15. Shader Interfaces

When a pipeline is created, the set of shaders specified in the corresponding Vk*PipelineCreateInfo structure are implicitly linked at a number of different interfaces.

Interface definitions make use of the following SPIR-V decorations:

  • DescriptorSet and Binding

  • Location, Component, and Index

  • Flat, NoPerspective, Centroid, and Sample

  • Block and BufferBlock

  • InputAttachmentIndex

  • Offset, ArrayStride, and MatrixStride

  • BuiltIn

  • PassthroughNV

This specification describes valid uses for Vulkan of these decorations. Any other use of one of these decorations is invalid, with the exception that, when using SPIR-V versions 1.4 and earlier: Block, BufferBlock, Offset, ArrayStride, and MatrixStride can also decorate types and type members used by variables in the Private and Function storage classes.

15.1. Shader Input and Output Interfaces

When multiple stages are present in a pipeline, the outputs of one stage form an interface with the inputs of the next stage. When such an interface involves a shader, shader outputs are matched against the inputs of the next stage, and shader inputs are matched against the outputs of the previous stage.

All the variables forming the shader input and output interfaces are listed as operands to the OpEntryPoint instruction and are declared with the Input or Output storage classes, respectively, in the SPIR-V module. These generally form the interfaces between consecutive shader stages, regardless of any non-shader stages between the consecutive shader stages.

There are two classes of variables that can be matched between shader stages, built-in variables and user-defined variables. Each class has a different set of matching criteria.

Output variables of a shader stage have undefined values until the shader writes to them or uses the Initializer operand when declaring the variable.

15.1.1. Built-in Interface Block

Shader built-in variables meeting the following requirements define the built-in interface block. They must

  • be explicitly declared (there are no implicit built-ins),

  • be identified with a BuiltIn decoration,

  • form object types as described in the Built-in Variables section, and

  • be declared in a block whose top-level members are the built-ins.

There must be no more than one built-in interface block per shader per interface.

Built-ins must not have any Location or Component decorations.

15.1.2. User-defined Variable Interface

The non-built-in variables listed by OpEntryPoint with the Input or Output storage class form the user-defined variable interface. These must have SPIR-V numerical types or, recursively, composite types of such types. By default, the components of such types have a width of 32 or 64 bits. If an implementation supports storageInputOutput16, components can also have a width of 16 bits. These variables must be identified with a Location decoration and can also be identified with a Component decoration.

15.1.3. Interface Matching

Interface matching rules only apply to built-ins when they are declared as members of the built-in interface block.

Tessellation control and mesh shader per-vertex output variables and blocks, and tessellation control, tessellation evaluation, and geometry shader per-vertex input variables and blocks are required to be declared as arrays, with each element representing input or output values for a single vertex of a multi-vertex primitive. For the purposes of interface matching, the outermost array dimension of such variables and blocks is ignored.

A user-defined output variable is considered to match an input variable in the subsequent stage if the two variables are declared with the same Location and Component decoration and match in type and decoration, except that interpolation decorations are not required to match. XfbBuffer, XfbStride, Offset, and Stream are also not required to match for the purposes of interface matching. For the purposes of interface matching, variables declared without a Component decoration are considered to have a Component decoration of zero.

Note

Matching rules for passthrough geometry shaders are slightly different and are described in the Passthrough Interface Matching section.

Variables or block members declared as structures are considered to match in type if and only if the structure members match in type, decoration, number, and declaration order. Variables or block members declared as arrays are considered to match in type only if both declarations specify the same element type and size.

At an interface between two non-fragment shader stages, the built-in interface block must match exactly, as described above, except for per-view outputs as described in Mesh Shader Per-View Outputs. At an interface involving the fragment shader inputs, the presence or absence of any built-in output does not affect the interface matching.

At an interface between two shader stages, the user-defined variable interface must match exactly, as described above.

Any input value to a shader stage is well-defined as long as the preceding stages writes to a matching output, as described above.

Additionally, scalar and vector inputs are well-defined if there is a corresponding output satisfying all of the following conditions:

  • the input and output match exactly in decoration,

  • the output is a vector with the same basic type and has at least as many components as the input, and

  • the common component type of the input and output is 16-bit integer or floating-point, or 32-bit integer or floating-point (64-bit component types are excluded).

In this case, the components of the input will be taken from the first components of the output, and any extra components of the output will be ignored.

15.1.4. Location Assignment

This section describes location assignments for user-defined variables and how many locations are consumed by a given user-variable type. As mentioned above, some inputs and outputs have an additional level of arrayness relative to other shader inputs and outputs. This outer array level is removed from the type before considering how many locations the type consumes.

The Location value specifies an interface slot comprised of a 32-bit four-component vector conveyed between stages. The Component specifies components within these vector locations. Only types with widths of 16, 32 or 64 are supported in shader interfaces.

Inputs and outputs of the following types consume a single interface location:

  • 16-bit scalar and vector types, and

  • 32-bit scalar and vector types, and

  • 64-bit scalar and 2-component vector types.

64-bit three- and four-component vectors consume two consecutive locations.

If a declared input or output is an array of size n and each element takes m locations, it will be assigned m × n consecutive locations starting with the location specified.

If the declared input or output is an n × m 16-, 32- or 64-bit matrix, it will be assigned multiple locations starting with the location specified. The number of locations assigned for each matrix will be the same as for an n-element array of m-component vectors.

An OpVariable with a structure type that is not a block must be decorated with a Location.

When an OpVariable with a structure type (either block or non-block) is decorated with a Location, the members in the structure type must not be decorated with a Location. The OpVariable’s members are assigned consecutive locations in declaration order, starting from the first member, which is assigned the location decoration from the OpVariable.

When a block-type OpVariable is declared without a Location decoration, each member in its structure type must be decorated with a Location. Types nested deeper than the top-level members must not have Location decorations.

The locations consumed by block and structure members are determined by applying the rules above in a depth-first traversal of the instantiated members as though the structure or block member were declared as an input or output variable of the same type.

Any two inputs listed as operands on the same OpEntryPoint must not be assigned the same location, either explicitly or implicitly. Any two outputs listed as operands on the same OpEntryPoint must not be assigned the same location, either explicitly or implicitly.

The number of input and output locations available for a shader input or output interface are limited, and dependent on the shader stage as described in Shader Input and Output Locations. All variables in both the built-in interface block and the user-defined variable interface count against these limits. Each effective Location must have a value less than the number of locations available for the given interface, as specified in the "Locations Available" column in Shader Input and Output Locations.

Table 18. Shader Input and Output Locations
Shader Interface Locations Available

vertex input

maxVertexInputAttributes

vertex output

maxVertexOutputComponents / 4

tessellation control input

maxTessellationControlPerVertexInputComponents / 4

tessellation control output

maxTessellationControlPerVertexOutputComponents / 4

tessellation evaluation input

maxTessellationEvaluationInputComponents / 4

tessellation evaluation output

maxTessellationEvaluationOutputComponents / 4

geometry input

maxGeometryInputComponents / 4

geometry output

maxGeometryOutputComponents / 4

fragment input

maxFragmentInputComponents / 4

fragment output

maxFragmentOutputAttachments

15.1.5. Component Assignment

The Component decoration allows the Location to be more finely specified for scalars and vectors, down to the individual components within a location that are consumed. The components within a location are 0, 1, 2, and 3. A variable or block member starting at component N will consume components N, N+1, N+2, …​ up through its size. For 16-, and 32-bit types, it is invalid if this sequence of components gets larger than 3. A scalar 64-bit type will consume two of these components in sequence, and a two-component 64-bit vector type will consume all four components available within a location. A three- or four-component 64-bit vector type must not specify a Component decoration. A three-component 64-bit vector type will consume all four components of the first location and components 0 and 1 of the second location. This leaves components 2 and 3 available for other component-qualified declarations.

A scalar or two-component 64-bit data type must not specify a Component decoration of 1 or 3. A Component decoration must not be specified for any type that is not a scalar or vector.

15.2. Vertex Input Interface

When the vertex stage is present in a pipeline, the vertex shader input variables form an interface with the vertex input attributes. The vertex shader input variables are matched by the Location and Component decorations to the vertex input attributes specified in the pVertexInputState member of the VkGraphicsPipelineCreateInfo structure.

The vertex shader input variables listed by OpEntryPoint with the Input storage class form the vertex input interface. These variables must be identified with a Location decoration and can also be identified with a Component decoration.

For the purposes of interface matching: variables declared without a Component decoration are considered to have a Component decoration of zero. The number of available vertex input locations is given by the maxVertexInputAttributes member of the VkPhysicalDeviceLimits structure.

All vertex shader inputs declared as above must have a corresponding attribute and binding in the pipeline.

15.3. Fragment Output Interface

When the fragment stage is present in a pipeline, the fragment shader outputs form an interface with the output attachments of the current subpass. The fragment shader output variables are matched by the Location and Component decorations to the color attachments specified in the pColorAttachments array of the VkSubpassDescription structure describing the subpass that the fragment shader is executed in.

The fragment shader output variables listed by OpEntryPoint with the Output storage class form the fragment output interface. These variables must be identified with a Location decoration. They can also be identified with a Component decoration and/or an Index decoration. For the purposes of interface matching: variables declared without a Component decoration are considered to have a Component decoration of zero, and variables declared without an Index decoration are considered to have an Index decoration of zero.

A fragment shader output variable identified with a Location decoration of i is directed to the color attachment indicated by pColorAttachments[i], after passing through the blending unit as described in Blending, if enabled. Locations are consumed as described in Location Assignment. The number of available fragment output locations is given by the maxFragmentOutputAttachments member of the VkPhysicalDeviceLimits structure.

Components of the output variables are assigned as described in Component Assignment. Output components identified as 0, 1, 2, and 3 will be directed to the R, G, B, and A inputs to the blending unit, respectively, or to the output attachment if blending is disabled. If two variables are placed within the same location, they must have the same underlying type (floating-point or integer). The input values to blending or color attachment writes are undefined for components which do not correspond to a fragment shader output.

Fragment outputs identified with an Index of zero are directed to the first input of the blending unit associated with the corresponding Location. Outputs identified with an Index of one are directed to the second input of the corresponding blending unit.

No component aliasing of output variables is allowed, that is there must not be two output variables which have the same location, component, and index, either explicitly declared or implied.

Output values written by a fragment shader must be declared with either OpTypeFloat or OpTypeInt, and a Width of 32. If storageInputOutput16 is supported, output values written by a fragment shader can be also declared with either OpTypeFloat or OpTypeInt and a Width of 16. Composites of these types are also permitted. If the color attachment has a signed or unsigned normalized fixed-point format, color values are assumed to be floating-point and are converted to fixed-point as described in Conversion from Floating-Point to Normalized Fixed-Point; If the color attachment has an integer format, color values are assumed to be integers and converted to the bit-depth of the target. Any value that cannot be represented in the attachment’s format is undefined. For any other attachment format no conversion is performed. If the type of the values written by the fragment shader do not match the format of the corresponding color attachment, the resulting values are undefined for those components.

15.4. Fragment Input Attachment Interface

When a fragment stage is present in a pipeline, the fragment shader subpass inputs form an interface with the input attachments of the current subpass. The fragment shader subpass input variables are matched by InputAttachmentIndex decorations to the input attachments specified in the pInputAttachments array of the VkSubpassDescription structure describing the subpass that the fragment shader is executed in.

The fragment shader subpass input variables with the UniformConstant storage class and a decoration of InputAttachmentIndex that are statically used by OpEntryPoint form the fragment input attachment interface. These variables must be declared with a type of OpTypeImage, a Dim operand of SubpassData, and a Sampled operand of 2.

A subpass input variable identified with an InputAttachmentIndex decoration of i reads from the input attachment indicated by pInputAttachments[i] member of VkSubpassDescription. If the subpass input variable is declared as an array of size N, it consumes N consecutive input attachments, starting with the index specified. There must not be more than one input variable with the same InputAttachmentIndex whether explicitly declared or implied by an array declaration. The number of available input attachment indices is given by the maxPerStageDescriptorInputAttachments member of the VkPhysicalDeviceLimits structure.

Variables identified with the InputAttachmentIndex must only be used by a fragment stage. The basic data type (floating-point, integer, unsigned integer) of the subpass input must match the basic format of the corresponding input attachment, or the values of subpass loads from these variables are undefined.

See Input Attachment for more details.

15.5. Ray Tracing Pipeline Interface

Ray tracing pipelines may have more stages than other pipelines with multiple instances of each stage and more dynamic interactions between the stages, but still has interface structures that obey the same generally rules as interfaces between shader stages in other pipelines. The three types of inter-stage interface variables for ray tracing pipelines are:

  • Ray payloads which contain data tracked for the entire lifetime of the ray.

  • Hit attributes which contain data about a specific hit for the duration of its processing.

  • Callable data for passing data into and out of a callable shader.

Ray payloads and callable data are used in explicit shader call instructions, so they have an incoming variant to distinguish the parameter passed to the invocation from any other payloads or data being used by subsequent shader call instructions.

An interface structure used between stages must match between the stages using it. Specifically:

  • The hit attribute structure read in an any-hit or closest hit shader must be the same structure as the hit attribute structure written in the corresponding intersection shader in the same hit group.

  • The incoming callable data for a callable shader must be the same structure as the callable data referenced by the execute callable instruction in the calling shader.

  • The ray payload for a shader invoked by a trace ray command must be the same structure for all shader stages using the payload for that ray.

Any shader with an incoming ray payload, incoming callable data, or hit attribute must only declare one variable of that type.

Table 19. Ray Pipeline Shader Interface
Shader Stage Ray Payload Incoming Ray Payload Hit Attribute Callable Data Incoming Callable Data

Ray Generation

r/w

r/w

r/w

Intersection

r/w

Any-Hit

r

Closest Hit

r/w

r/w

r

r/w

Miss

r/w

r/w

r/w

Callable

r/w

r/w

15.6. Shader Resource Interface

When a shader stage accesses buffer or image resources, as described in the Resource Descriptors section, the shader resource variables must be matched with the pipeline layout that is provided at pipeline creation time.

The set of shader variables that form the shader resource interface for a stage are the variables statically used by that stage’s OpEntryPoint with a storage class of Uniform, UniformConstant, StorageBuffer, or PushConstant. For the fragment shader, this includes the fragment input attachment interface.

The shader resource interface consists of two sub-interfaces: the push constant interface and the descriptor set interface.

15.6.1. Push Constant Interface

The shader variables defined with a storage class of PushConstant that are statically used by the shader entry points for the pipeline define the push constant interface. They must be:

  • typed as OpTypeStruct,

  • identified with a Block decoration, and

  • laid out explicitly using the Offset, ArrayStride, and MatrixStride decorations as specified in Offset and Stride Assignment.

There must be no more than one push constant block statically used per shader entry point.

Each statically used member of a push constant block must be placed at an Offset such that the entire member is entirely contained within the VkPushConstantRange for each OpEntryPoint that uses it, and the stageFlags for that range must specify the appropriate VkShaderStageFlagBits for that stage. The Offset decoration for any member of a push constant block must not cause the space required for that member to extend outside the range [0, maxPushConstantsSize).

Any member of a push constant block that is declared as an array must only be accessed with dynamically uniform indices.

15.6.2. Descriptor Set Interface

The descriptor set interface is comprised of the shader variables with the storage class of StorageBuffer, Uniform or UniformConstant (including the variables in the fragment input attachment interface) that are statically used by the shader entry points for the pipeline.

These variables must have DescriptorSet and Binding decorations specified, which are assigned and matched with the VkDescriptorSetLayout objects in the pipeline layout as described in DescriptorSet and Binding Assignment.

The Image Format of an OpTypeImage declaration must not be Unknown, for variables which are used for OpImageRead, OpImageSparseRead, or OpImageWrite operations, except under the following conditions:

  • For OpImageWrite, if the shaderStorageImageWriteWithoutFormat feature is enabled and the shader module declares the StorageImageWriteWithoutFormat capability.

  • For OpImageRead or OpImageSparseRead, if the shaderStorageImageReadWithoutFormat feature is enabled and the shader module declares the StorageImageReadWithoutFormat capability.

  • For OpImageRead, if Dim is SubpassData (indicating a read from an input attachment).

The Image Format of an OpTypeImage declaration must not be Unknown, for variables which are used for OpAtomic* operations.

Variables identified with the Uniform storage class are used to access transparent buffer backed resources. Such variables must be:

  • typed as OpTypeStruct, or an array of this type,

  • identified with a Block or BufferBlock decoration, and

  • laid out explicitly using the Offset, ArrayStride, and MatrixStride decorations as specified in Offset and Stride Assignment.

Variables identified with the StorageBuffer storage class are used to access transparent buffer backed resources. Such variables must be:

  • typed as OpTypeStruct, or an array of this type,

  • identified with a Block decoration, and

  • laid out explicitly using the Offset, ArrayStride, and MatrixStride decorations as specified in Offset and Stride Assignment.

The Offset decoration for any member of a Block-decorated variable in the Uniform storage class must not cause the space required for that variable to extend outside the range [0, maxUniformBufferRange). The Offset decoration for any member of a Block-decorated variable in the StorageBuffer storage class must not cause the space required for that variable to extend outside the range [0, maxStorageBufferRange).

Variables identified with the Uniform storage class can also be used to access transparent descriptor set backed resources when the variable is assigned to a descriptor set layout binding with a descriptorType of VK_DESCRIPTOR_TYPE_INLINE_UNIFORM_BLOCK_EXT. In this case the variable must be typed as OpTypeStruct and cannot be aggregated into arrays of that type. Further, the Offset decoration for any member of such a variable must not cause the space required for that variable to extend outside the range [0,maxInlineUniformBlockSize).

Variables identified with a storage class of UniformConstant and a decoration of InputAttachmentIndex must be declared as described in Fragment Input Attachment Interface.

SPIR-V variables decorated with a descriptor set and binding that identify a combined image sampler descriptor can have a type of OpTypeImage, OpTypeSampler (Sampled=1), or OpTypeSampledImage.

Arrays of any of these types can be indexed with constant integral expressions. The following features must be enabled and capabilities must be declared in order to index such arrays with dynamically uniform or non-uniform indices:

  • Storage images (except storage texel buffers and input attachments):

    • Dynamically uniform: shaderStorageImageArrayDynamicIndexing and StorageImageArrayDynamicIndexing

    • Non-uniform: shaderStorageImageArrayNonUniformIndexing and StorageImageArrayNonUniformIndexing

  • Storage texel buffers:

    • Dynamically uniform: shaderStorageTexelBufferArrayDynamicIndexing and StorageTexelBufferArrayDynamicIndexing

    • Non-uniform: shaderStorageTexelBufferArrayNonUniformIndexing and StorageTexelBufferArrayNonUniformIndexing

  • Input attachments:

    • Dynamically uniform: shaderInputAttachmentArrayDynamicIndexing and InputAttachmentArrayDynamicIndexing

    • Non-uniform: shaderInputAttachmentArrayNonUniformIndexing and InputAttachmentArrayNonUniformIndexing

  • Sampled images (except uniform texel buffers), samplers and combined image samplers:

    • Dynamically uniform: shaderSampledImageArrayDynamicIndexing and SampledImageArrayDynamicIndexing

    • Non-uniform: shaderSampledImageArrayNonUniformIndexing and SampledImageArrayNonUniformIndexing

  • Uniform texel buffers:

    • Dynamically uniform: shaderUniformTexelBufferArrayDynamicIndexing and UniformTexelBufferArrayDynamicIndexing

    • Non-uniform: shaderUniformTexelBufferArrayNonUniformIndexing and UniformTexelBufferArrayNonUniformIndexing

  • Uniform buffers:

    • Dynamically uniform: shaderUniformBufferArrayDynamicIndexing and UniformBufferArrayDynamicIndexing

    • Non-uniform: shaderUniformBufferArrayNonUniformIndexing and UniformBufferArrayNonUniformIndexing

  • Storage buffers:

    • Dynamically uniform: shaderStorageBufferArrayDynamicIndexing and StorageBufferArrayDynamicIndexing

    • Non-uniform: shaderStorageBufferArrayNonUniformIndexing and StorageBufferArrayNonUniformIndexing

  • Acceleration structures:

    • Dynamically uniform: Always supported.

    • Non-uniform: Always supported.

If an instruction loads from or stores to a resource (including atomics and image instructions) and the resource descriptor being accessed is not dynamically uniform, then the corresponding non-uniform indexing feature must be enabled and the capability must be declared. If an instruction loads from or stores to a resource (including atomics and image instructions) and the resource descriptor being accessed is loaded from an array element with a non-constant index, then the corresponding dynamic or non-uniform indexing feature must be enabled and the capability must be declared.

If the combined image sampler enables sampler Y′CBCR conversion or samples a subsampled image, it must be indexed only by constant integral expressions when aggregated into arrays in shader code, irrespective of the shaderSampledImageArrayDynamicIndexing feature.

Table 20. Shader Resource and Descriptor Type Correspondence
Resource type Descriptor Type

sampler

VK_DESCRIPTOR_TYPE_SAMPLER or VK_DESCRIPTOR_TYPE_COMBINED_IMAGE_SAMPLER

sampled image

VK_DESCRIPTOR_TYPE_SAMPLED_IMAGE or VK_DESCRIPTOR_TYPE_COMBINED_IMAGE_SAMPLER

storage image

VK_DESCRIPTOR_TYPE_STORAGE_IMAGE

combined image sampler

VK_DESCRIPTOR_TYPE_COMBINED_IMAGE_SAMPLER

uniform texel buffer

VK_DESCRIPTOR_TYPE_UNIFORM_TEXEL_BUFFER

storage texel buffer

VK_DESCRIPTOR_TYPE_STORAGE_TEXEL_BUFFER

uniform buffer

VK_DESCRIPTOR_TYPE_UNIFORM_BUFFER or VK_DESCRIPTOR_TYPE_UNIFORM_BUFFER_DYNAMIC

storage buffer

VK_DESCRIPTOR_TYPE_STORAGE_BUFFER or VK_DESCRIPTOR_TYPE_STORAGE_BUFFER_DYNAMIC

input attachment

VK_DESCRIPTOR_TYPE_INPUT_ATTACHMENT

inline uniform block

VK_DESCRIPTOR_TYPE_INLINE_UNIFORM_BLOCK_EXT

acceleration structure

VK_DESCRIPTOR_TYPE_ACCELERATION_STRUCTURE_KHR or VK_DESCRIPTOR_TYPE_ACCELERATION_STRUCTURE_NV

Table 21. Shader Resource and Storage Class Correspondence
Resource type Storage Class Type Decoration(s)1

sampler

UniformConstant

OpTypeSampler

sampled image

UniformConstant

OpTypeImage (Sampled=1)

storage image

UniformConstant

OpTypeImage (Sampled=2)

combined image sampler

UniformConstant

OpTypeSampledImage
OpTypeImage (Sampled=1)
OpTypeSampler

uniform texel buffer

UniformConstant

OpTypeImage (Dim=Buffer, Sampled=1)

storage texel buffer

UniformConstant

OpTypeImage (Dim=Buffer, Sampled=2)

uniform buffer

Uniform

OpTypeStruct

Block, Offset, (ArrayStride), (MatrixStride)

storage buffer

Uniform

OpTypeStruct

BufferBlock, Offset, (ArrayStride), (MatrixStride)

StorageBuffer

Block, Offset, (ArrayStride), (MatrixStride)

input attachment

UniformConstant

OpTypeImage (Dim=SubpassData, Sampled=2)

InputAttachmentIndex

inline uniform block

Uniform

OpTypeStruct

Block, Offset, (ArrayStride), (MatrixStride)

acceleration structure

UniformConstant

OpTypeAccelerationStructureKHR

1

in addition to DescriptorSet and Binding

15.6.3. DescriptorSet and Binding Assignment

A variable decorated with a DescriptorSet decoration of s and a Binding decoration of b indicates that this variable is associated with the VkDescriptorSetLayoutBinding that has a binding equal to b in pSetLayouts[s] that was specified in VkPipelineLayoutCreateInfo.

DescriptorSet decoration values must be between zero and maxBoundDescriptorSets minus one, inclusive. Binding decoration values can be any 32-bit unsigned integer value, as described in Descriptor Set Layout. Each descriptor set has its own binding name space.

If the Binding decoration is used with an array, the entire array is assigned that binding value. The array must be a single-dimensional array and size of the array must be no larger than the number of descriptors in the binding. If the array is runtime-sized, then array elements greater than or equal to the size of that binding in the bound descriptor set must not be used. If the array is runtime-sized, the runtimeDescriptorArray feature must be enabled and the RuntimeDescriptorArray capability must be declared. The index of each element of the array is referred to as the arrayElement. For the purposes of interface matching and descriptor set operations, if a resource variable is not an array, it is treated as if it has an arrayElement of zero.

There is a limit on the number of resources of each type that can be accessed by a pipeline stage as shown in Shader Resource Limits. The “Resources Per Stage” column gives the limit on the number each type of resource that can be statically used for an entry point in any given stage in a pipeline. The “Resource Types” column lists which resource types are counted against the limit. Some resource types count against multiple limits.

The pipeline layout may include descriptor sets and bindings which are not referenced by any variables statically used by the entry points for the shader stages in the binding’s stageFlags.

However, if a variable assigned to a given DescriptorSet and Binding is statically used by the entry point for a shader stage, the pipeline layout must contain a descriptor set layout binding in that descriptor set layout and for that binding number, and that binding’s stageFlags must include the appropriate VkShaderStageFlagBits for that stage. The variable must be of a valid resource type determined by its SPIR-V type and storage class, as defined in Shader Resource and Storage Class Correspondence. The descriptor set layout binding must be of a corresponding descriptor type, as defined in Shader Resource and Descriptor Type Correspondence.

Note

There are no limits on the number of shader variables that can have overlapping set and binding values in a shader; but which resources are statically used has an impact. If any shader variable identifying a resource is statically used in a shader, then the underlying descriptor bound at the declared set and binding must support the declared type in the shader when the shader executes.

If multiple shader variables are declared with the same set and binding values, and with the same underlying descriptor type, they can all be statically used within the same shader. However, accesses are not automatically synchronized, and Aliased decorations should be used to avoid data hazards (see section 2.18.2 Aliasing in the SPIR-V specification).

If multiple shader variables with the same set and binding values are declared in a single shader, but with different declared types, where any of those are not supported by the relevant bound descriptor, that shader can only be executed if the variables with the unsupported type are not statically used.

A noteworthy example of using multiple statically-used shader variables sharing the same descriptor set and binding values is a descriptor of type VK_DESCRIPTOR_TYPE_COMBINED_IMAGE_SAMPLER that has multiple corresponding shader variables in the UniformConstant storage class, where some could be OpTypeImage, some could be OpTypeSampler (Sampled=1), and some could be OpTypeSampledImage.

Table 22. Shader Resource Limits
Resources per Stage Resource Types

maxPerStageDescriptorSamplers or maxPerStageDescriptorUpdateAfterBindSamplers

sampler

combined image sampler

maxPerStageDescriptorSampledImages or maxPerStageDescriptorUpdateAfterBindSampledImages

sampled image

combined image sampler

uniform texel buffer

maxPerStageDescriptorStorageImages or maxPerStageDescriptorUpdateAfterBindStorageImages

storage image

storage texel buffer

maxPerStageDescriptorUniformBuffers or maxPerStageDescriptorUpdateAfterBindUniformBuffers

uniform buffer

uniform buffer dynamic

maxPerStageDescriptorStorageBuffers or maxPerStageDescriptorUpdateAfterBindStorageBuffers

storage buffer

storage buffer dynamic

maxPerStageDescriptorInputAttachments or maxPerStageDescriptorUpdateAfterBindInputAttachments

input attachment1

maxPerStageDescriptorInlineUniformBlocks or maxPerStageDescriptorUpdateAfterBindInlineUniformBlocks

inline uniform block

VkPhysicalDeviceRayTracingPropertiesNV ::maxDescriptorSetAccelerationStructures or maxPerStageDescriptorAccelerationStructures or maxPerStageDescriptorUpdateAfterBindAccelerationStructures

acceleration structure

1

Input attachments can only be used in the fragment shader stage

15.6.4. Offset and Stride Assignment

Certain objects must be explicitly laid out using the Offset, ArrayStride, and MatrixStride, as described in SPIR-V explicit layout validation rules. All such layouts also must conform to the following requirements.

Note

The numeric order of Offset decorations does not need to follow member declaration order.

Alignment Requirements

There are different alignment requirements depending on the specific resources and on the features enabled on the device.

The scalar alignment of the type of an OpTypeStruct member is defined recursively as follows:

  • A scalar of size N has a scalar alignment of N.

  • A vector or matrix type has a scalar alignment equal to that of its component type.

  • An array type has a scalar alignment equal to that of its element type.

  • A structure has a scalar alignment equal to the largest scalar alignment of any of its members.

The base alignment of the type of an OpTypeStruct member is defined recursively as follows:

  • A scalar has a base alignment equal to its scalar alignment.

  • A two-component vector has a base alignment equal to twice its scalar alignment.

  • A three- or four-component vector has a base alignment equal to four times its scalar alignment.

  • An array has a base alignment equal to the base alignment of its element type.

  • A structure has a base alignment equal to the largest base alignment of any of its members.

  • A row-major matrix of C columns has a base alignment equal to the base alignment of a vector of C matrix components.

  • A column-major matrix has a base alignment equal to the base alignment of the matrix column type.

The extended alignment of the type of an OpTypeStruct member is similarly defined as follows:

  • A scalar, vector or matrix type has an extended alignment equal to its base alignment.

  • An array or structure type has an extended alignment equal to the largest extended alignment of any of its members, rounded up to a multiple of 16.

A member is defined to improperly straddle if either of the following are true:

  • It is a vector with total size less than or equal to 16 bytes, and has Offset decorations placing its first byte at F and its last byte at L, where floor(F / 16) != floor(L / 16).

  • It is a vector with total size greater than 16 bytes and has its Offset decorations placing its first byte at a non-integer multiple of 16.

Standard Buffer Layout

Every member of an OpTypeStruct that is required to be explicitly laid out must be aligned according to the first matching rule as follows. If the struct is contained in pointer types of multiple storage classes, it must satisfy the requirements for every storage class used to reference it.

  1. If the scalarBlockLayout feature is enabled on the device then every member must be aligned according to its scalar alignment.

  2. All vectors must be aligned according to their scalar alignment.

  3. If the uniformBufferStandardLayout feature is not enabled on the device, then any member of an OpTypeStruct with a storage class of Uniform and a decoration of Block must be aligned according to its extended alignment.

  4. Every other member must be aligned according to its base alignment.

Note

Even if scalar alignment is supported, it is generally more performant to use the base alignment.

The memory layout must obey the following rules:

  • The Offset decoration of any member must be a multiple of its alignment.

  • Any ArrayStride or MatrixStride decoration must be a multiple of the alignment of the array or matrix as defined above.

Unless the scalarBlockLayout feature is enabled on the device:

  • Vectors must not improperly straddle, as defined above.

  • The Offset decoration of a member must not place it between the end of a structure or an array and the next multiple of the alignment of that structure or array.

Note

The std430 layout in GLSL satisfies these rules for types using the base alignment. The std140 layout satisfies the rules for types using the extended alignment.

15.7. Built-In Variables

Built-in variables are accessed in shaders by declaring a variable decorated with a BuiltIn SPIR-V decoration. The meaning of each BuiltIn decoration is as follows. In the remainder of this section, the name of a built-in is used interchangeably with a term equivalent to a variable decorated with that particular built-in. Built-ins that represent integer values can be declared as either signed or unsigned 32-bit integers.

As mentioned above, some inputs and outputs have an additional level of arrayness relative to other shader inputs and outputs. This level of arrayness is not included in the type descriptions below, but must be included when declaring the built-in.

BaryCoordNV

The BaryCoordNV decoration can be used to decorate a fragment shader input variable. This variable will contain a three-component floating-point vector with barycentric weights that indicate the location of the fragment relative to the screen-space locations of vertices of its primitive, obtained using perspective interpolation.

Valid Usage
  • VUID-BaryCoordNV-BaryCoordNV-04154
    The BaryCoordNV decoration must be used only within the Fragment Execution Model

  • VUID-BaryCoordNV-BaryCoordNV-04155
    The variable decorated with BaryCoordNV must be declared using the Input Storage Class

  • VUID-BaryCoordNV-BaryCoordNV-04156
    The variable decorated with BaryCoordNV must be declared as a three-component vector of 32-bit floating-point values

BaryCoordNoPerspAMD

The BaryCoordNoPerspAMD decoration can be used to decorate a fragment shader input variable. This variable will contain the (I,J) pair of the barycentric coordinates corresponding to the fragment evaluated using linear interpolation at the fragment’s center. The K coordinate of the barycentric coordinates can be derived given the identity I + J + K = 1.0.

Valid Usage
  • VUID-BaryCoordNoPerspAMD-BaryCoordNoPerspAMD-04157
    The BaryCoordNoPerspAMD decoration must be used only within the Fragment Execution Model

  • VUID-BaryCoordNoPerspAMD-BaryCoordNoPerspAMD-04158
    The variable decorated with BaryCoordNoPerspAMD must be declared using the Input Storage Class

  • VUID-BaryCoordNoPerspAMD-BaryCoordNoPerspAMD-04159
    The variable decorated with BaryCoordNoPerspAMD must be declared as a two-component vector of 32-bit floating-point values

BaryCoordNoPerspNV

The BaryCoordNoPerspNV decoration can be used to decorate a fragment shader input variable. This variable will contain a three-component floating-point vector with barycentric weights that indicate the location of the fragment relative to the screen-space locations of vertices of its primitive, obtained using linear interpolation.

Valid Usage
  • VUID-BaryCoordNoPerspNV-BaryCoordNoPerspNV-04160
    The BaryCoordNoPerspNV decoration must be used only within the Fragment Execution Model

  • VUID-BaryCoordNoPerspNV-BaryCoordNoPerspNV-04161
    The variable decorated with BaryCoordNoPerspNV must be declared using the Input Storage Class

  • VUID-BaryCoordNoPerspNV-BaryCoordNoPerspNV-04162
    The variable decorated with BaryCoordNoPerspNV must be declared as a three-component vector of 32-bit floating-point values

BaryCoordNoPerspCentroidAMD

The BaryCoordNoPerspCentroidAMD decoration can be used to decorate a fragment shader input variable. This variable will contain the (I,J) pair of the barycentric coordinates corresponding to the fragment evaluated using linear interpolation at the centroid. The K coordinate of the barycentric coordinates can be derived given the identity I + J + K = 1.0.

Valid Usage
  • VUID-BaryCoordNoPerspCentroidAMD-BaryCoordNoPerspCentroidAMD-04163
    The BaryCoordNoPerspCentroidAMD decoration must be used only within the Fragment Execution Model

  • VUID-BaryCoordNoPerspCentroidAMD-BaryCoordNoPerspCentroidAMD-04164
    The variable decorated with BaryCoordNoPerspCentroidAMD must be declared using the Input Storage Class

  • VUID-BaryCoordNoPerspCentroidAMD-BaryCoordNoPerspCentroidAMD-04165
    The variable decorated with BaryCoordNoPerspCentroidAMD must be declared as a three-component vector of 32-bit floating-point values

BaryCoordNoPerspSampleAMD

The BaryCoordNoPerspSampleAMD decoration can be used to decorate a fragment shader input variable. This variable will contain the (I,J) pair of the barycentric coordinates corresponding to the fragment evaluated using linear interpolation at each covered sample. The K coordinate of the barycentric coordinates can be derived given the identity I + J + K = 1.0.

Valid Usage
  • VUID-BaryCoordNoPerspSampleAMD-BaryCoordNoPerspSampleAMD-04166
    The BaryCoordNoPerspSampleAMD decoration must be used only within the Fragment Execution Model

  • VUID-BaryCoordNoPerspSampleAMD-BaryCoordNoPerspSampleAMD-04167
    The variable decorated with BaryCoordNoPerspSampleAMD must be declared using the Input Storage Class

  • VUID-BaryCoordNoPerspSampleAMD-BaryCoordNoPerspSampleAMD-04168
    The variable decorated with BaryCoordNoPerspSampleAMD must be declared as a two-component vector of 32-bit floating-point values

BaryCoordPullModelAMD

The BaryCoordPullModelAMD decoration can be used to decorate a fragment shader input variable. This variable will contain (1/W, 1/I, 1/J) evaluated at the fragment center and can be used to calculate gradients and then interpolate I, J, and W at any desired sample location.

Valid Usage
  • VUID-BaryCoordPullModelAMD-BaryCoordPullModelAMD-04169
    The BaryCoordPullModelAMD decoration must be used only within the Fragment Execution Model

  • VUID-BaryCoordPullModelAMD-BaryCoordPullModelAMD-04170
    The variable decorated with BaryCoordPullModelAMD must be declared using the Input Storage Class

  • VUID-BaryCoordPullModelAMD-BaryCoordPullModelAMD-04171
    The variable decorated with BaryCoordPullModelAMD must be declared as a three-component vector of 32-bit floating-point values

BaryCoordSmoothAMD

The BaryCoordSmoothAMD decoration can be used to decorate a fragment shader input variable. This variable will contain the (I,J) pair of the barycentric coordinates corresponding to the fragment evaluated using perspective interpolation at the fragment’s center. The K coordinate of the barycentric coordinates can be derived given the identity I + J + K = 1.0.

Valid Usage
  • VUID-BaryCoordSmoothAMD-BaryCoordSmoothAMD-04172
    The BaryCoordSmoothAMD decoration must be used only within the Fragment Execution Model

  • VUID-BaryCoordSmoothAMD-BaryCoordSmoothAMD-04173
    The variable decorated with BaryCoordSmoothAMD must be declared using the Input Storage Class

  • VUID-BaryCoordSmoothAMD-BaryCoordSmoothAMD-04174
    The variable decorated with BaryCoordSmoothAMD must be declared as a two-component vector of 32-bit floating-point values

BaryCoordSmoothCentroidAMD

The BaryCoordSmoothCentroidAMD decoration can be used to decorate a fragment shader input variable. This variable will contain the (I,J) pair of the barycentric coordinates corresponding to the fragment evaluated using perspective interpolation at the centroid. The K coordinate of the barycentric coordinates can be derived given the identity I + J + K = 1.0.

Valid Usage
  • VUID-BaryCoordSmoothCentroidAMD-BaryCoordSmoothCentroidAMD-04175
    The BaryCoordSmoothCentroidAMD decoration must be used only within the Fragment Execution Model

  • VUID-BaryCoordSmoothCentroidAMD-BaryCoordSmoothCentroidAMD-04176
    The variable decorated with BaryCoordSmoothCentroidAMD must be declared using the Input Storage Class

  • VUID-BaryCoordSmoothCentroidAMD-BaryCoordSmoothCentroidAMD-04177
    The variable decorated with BaryCoordSmoothCentroidAMD must be declared as a two-component vector of 32-bit floating-point values

BaryCoordSmoothSampleAMD

The BaryCoordSmoothSampleAMD decoration can be used to decorate a fragment shader input variable. This variable will contain the (I,J) pair of the barycentric coordinates corresponding to the fragment evaluated using perspective interpolation at each covered sample. The K coordinate of the barycentric coordinates can be derived given the identity I + J + K = 1.0.

Valid Usage
  • VUID-BaryCoordSmoothSampleAMD-BaryCoordSmoothSampleAMD-04178
    The BaryCoordSmoothSampleAMD decoration must be used only within the Fragment Execution Model

  • VUID-BaryCoordSmoothSampleAMD-BaryCoordSmoothSampleAMD-04179
    The variable decorated with BaryCoordSmoothSampleAMD must be declared using the Input Storage Class

  • VUID-BaryCoordSmoothSampleAMD-BaryCoordSmoothSampleAMD-04180
    The variable decorated with BaryCoordSmoothSampleAMD must be declared as a two-component vector of 32-bit floating-point values

BaseInstance

Decorating a variable with the BaseInstance built-in will make that variable contain the integer value corresponding to the first instance that was passed to the command that invoked the current vertex shader invocation. BaseInstance is the firstInstance parameter to a direct drawing command or the firstInstance member of a structure consumed by an indirect drawing command.

Valid Usage
  • VUID-BaseInstance-BaseInstance-04181
    The BaseInstance decoration must be used only within the Vertex Execution Model

  • VUID-BaseInstance-BaseInstance-04182
    The variable decorated with BaseInstance must be declared using the Input Storage Class

  • VUID-BaseInstance-BaseInstance-04183
    The variable decorated with BaseInstance must be declared as a scalar 32-bit integer value

BaseVertex

Decorating a variable with the BaseVertex built-in will make that variable contain the integer value corresponding to the first vertex or vertex offset that was passed to the command that invoked the current vertex shader invocation. For non-indexed drawing commands, this variable is the firstVertex parameter to a direct drawing command or the firstVertex member of the structure consumed by an indirect drawing command. For indexed drawing commands, this variable is the vertexOffset parameter to a direct drawing command or the vertexOffset member of the structure consumed by an indirect drawing command.

Valid Usage
  • VUID-BaseVertex-BaseVertex-04184
    The BaseVertex decoration must be used only within the Vertex Execution Model

  • VUID-BaseVertex-BaseVertex-04185
    The variable decorated with BaseVertex must be declared using the Input Storage Class

  • VUID-BaseVertex-BaseVertex-04186
    The variable decorated with BaseVertex must be declared as a scalar 32-bit integer value

ClipDistance

Decorating a variable with the ClipDistance built-in decoration will make that variable contain the mechanism for controlling user clipping. ClipDistance is an array such that the ith element of the array specifies the clip distance for plane i. A clip distance of 0 means the vertex is on the plane, a positive distance means the vertex is inside the clip half-space, and a negative distance means the point is outside the clip half-space.

Note

The array variable decorated with ClipDistance is explicitly sized by the shader.

Note

In the last vertex processing stage, these values will be linearly interpolated across the primitive and the portion of the primitive with interpolated distances less than 0 will be considered outside the clip volume. If ClipDistance is then used by a fragment shader, ClipDistance contains these linearly interpolated values.

Valid Usage
  • VUID-ClipDistance-ClipDistance-04187
    The ClipDistance decoration must be used only within the MeshNV, Vertex, Fragment, TessellationControl, TessellationEvaluation, or Geometry Execution Model

  • VUID-ClipDistance-ClipDistance-04188
    The variable decorated with ClipDistance within the MeshNV or Vertex Execution Model must be declared using the Output Storage Class

  • VUID-ClipDistance-ClipDistance-04189
    The variable decorated with ClipDistance within the Fragment Execution Model must be declared using the Input Storage Class

  • VUID-ClipDistance-ClipDistance-04190
    The variable decorated with ClipDistance within the TessellationControl, TessellationEvaluation, or Geometry Execution Model must not be declared in a Storage Class other than Input or Output

  • VUID-ClipDistance-ClipDistance-04191
    The variable decorated with ClipDistance must be declared as an array of 32-bit floating-point values

ClipDistancePerViewNV

Decorating a variable with the ClipDistancePerViewNV built-in decoration will make that variable contain the per-view clip distances. The per-view clip distances have the same semantics as ClipDistance.

Valid Usage
  • VUID-ClipDistancePerViewNV-ClipDistancePerViewNV-04192
    The ClipDistancePerViewNV decoration must be used only within the MeshNV Execution Model

  • VUID-ClipDistancePerViewNV-ClipDistancePerViewNV-04193
    The variable decorated with ClipDistancePerViewNV must be declared using the Output Storage Class

  • VUID-ClipDistancePerViewNV-ClipDistancePerViewNV-04194
    The variable decorated with ClipDistancePerViewNV must also be decorated with the PerViewNV decoration.

  • VUID-ClipDistancePerViewNV-ClipDistancePerViewNV-04195
    The variable decorated with ClipDistancePerViewNV must be declared as a two-dimensional array of 32-bit floating-point values

CullDistance

Decorating a variable with the CullDistance built-in decoration will make that variable contain the mechanism for controlling user culling. If any member of this array is assigned a negative value for all vertices belonging to a primitive, then the primitive is discarded before rasterization.

Note

In fragment shaders, the values of the CullDistance array are linearly interpolated across each primitive.

Note

If CullDistance decorates an input variable, that variable will contain the corresponding value from the CullDistance decorated output variable from the previous shader stage.

Valid Usage
  • VUID-CullDistance-CullDistance-04196
    The CullDistance decoration must be used only within the MeshNV, Vertex, Fragment, TessellationControl, TessellationEvaluation, or Geometry Execution Model

  • VUID-CullDistance-CullDistance-04197
    The variable decorated with CullDistance within the MeshNV or Vertex Execution Model must be declared using the Output Storage Class

  • VUID-CullDistance-CullDistance-04198
    The variable decorated with CullDistance within the Fragment Execution Model must be declared using the Input Storage Class

  • VUID-CullDistance-CullDistance-04199
    The variable decorated with CullDistance within the TessellationControl, TessellationEvaluation, or Geometry Execution Model must not be declared using a Storage Class other than Input or Output

  • VUID-CullDistance-CullDistance-04200
    The variable decorated with CullDistance must be declared as an array of 32-bit floating-point values

CullDistancePerViewNV

Decorating a variable with the CullDistancePerViewNV built-in decoration will make that variable contain the per-view cull distances. The per-view clip distances have the same semantics as CullDistance.

Valid Usage
  • VUID-CullDistancePerViewNV-CullDistancePerViewNV-04201
    The CullDistancePerViewNV decoration must be used only within the MeshNV Execution Model

  • VUID-CullDistancePerViewNV-CullDistancePerViewNV-04202
    The variable decorated with CullDistancePerViewNV must be declared using the Output Storage Class

  • VUID-CullDistancePerViewNV-CullDistancePerViewNV-04203
    The variable decorated with CullDistancePerViewNV must also be decorated with the PerViewNV decoration.

  • VUID-CullDistancePerViewNV-CullDistancePerViewNV-04204
    The variable decorated with CullDistancePerViewNV must be declared as a two-dimensional array of 32-bit floating-point values

DeviceIndex

The DeviceIndex decoration can be applied to a shader input which will be filled with the device index of the physical device that is executing the current shader invocation. This value will be in the range , where physicalDeviceCount is the physicalDeviceCount member of VkDeviceGroupDeviceCreateInfo.

Valid Usage
  • VUID-DeviceIndex-DeviceIndex-04205
    The variable decorated with DeviceIndex must be declared using the Input Storage Class

  • VUID-DeviceIndex-DeviceIndex-04206
    The variable decorated with DeviceIndex must be declared as a scalar 32-bit integer value

DrawIndex

Decorating a variable with the DrawIndex built-in will make that variable contain the integer value corresponding to the zero-based index of the drawing command that invoked the current task, mesh, or vertex shader invocation. For indirect drawing commands, DrawIndex begins at zero and increments by one for each draw command executed. The number of draw commands is given by the drawCount parameter. For direct drawing commands, DrawIndex is always zero. DrawIndex is dynamically uniform.

When task or mesh shaders are used, only the first active stage will have proper access to the variable. The value read by other stages is undefined.

Valid Usage
  • VUID-DrawIndex-DrawIndex-04207
    The DrawIndex decoration must be used only within the Vertex, MeshNV, or TaskNV Execution Model

  • VUID-DrawIndex-DrawIndex-04208
    The variable decorated with DrawIndex must be declared using the Input Storage Class

  • VUID-DrawIndex-DrawIndex-04209
    The variable decorated with DrawIndex must be declared as a scalar 32-bit integer value

FragCoord

Decorating a variable with the FragCoord built-in decoration will make that variable contain the framebuffer coordinate of the fragment being processed. The (x,y) coordinate (0,0) is the upper left corner of the upper left pixel in the framebuffer.

When Sample Shading is enabled, the x and y components of FragCoord reflect the location of one of the samples corresponding to the shader invocation.

Otherwise, the x and y components of FragCoord reflect the location of the center of the fragment.

The z component of FragCoord is the interpolated depth value of the primitive.

The w component is the interpolated .

The Centroid interpolation decoration is ignored, but allowed, on FragCoord.

Valid Usage
  • VUID-FragCoord-FragCoord-04210
    The FragCoord decoration must be used only within the Fragment Execution Model

  • VUID-FragCoord-FragCoord-04211
    The variable decorated with FragCoord must be declared using the Input Storage Class

  • VUID-FragCoord-FragCoord-04212
    The variable decorated with FragCoord must be declared as a four-component vector of 32-bit floating-point values

FragDepth

To have a shader supply a fragment-depth value, the shader must declare the DepthReplacing execution mode. Such a shader’s fragment-depth value will come from the variable decorated with the FragDepth built-in decoration.

This value will be used for any subsequent depth testing performed by the implementation or writes to the depth attachment.

Valid Usage
  • VUID-FragDepth-FragDepth-04213
    The FragDepth decoration must be used only within the Fragment Execution Model

  • VUID-FragDepth-FragDepth-04214
    The variable decorated with FragDepth must be declared using the Output Storage Class

  • VUID-FragDepth-FragDepth-04215
    The variable decorated with FragDepth must be declared as a scalar 32-bit floating-point value

  • VUID-FragDepth-FragDepth-04216
    If the shader dynamically writes to the variable decorated with FragDepth, the DepthReplacing Execution Mode must be declared

FragInvocationCountEXT

Decorating a variable with the FragInvocationCountEXT built-in decoration will make that variable contain the maximum number of fragment shader invocations for the fragment, as determined by minSampleShading.

If Sample Shading is not enabled, FragInvocationCountEXT will be filled with a value of 1.

Valid Usage
  • VUID-FragInvocationCountEXT-FragInvocationCountEXT-04217
    The FragInvocationCountEXT decoration must be used only within the Fragment Execution Model

  • VUID-FragInvocationCountEXT-FragInvocationCountEXT-04218
    The variable decorated with FragInvocationCountEXT must be declared using the Input Storage Class

  • VUID-FragInvocationCountEXT-FragInvocationCountEXT-04219
    The variable decorated with FragInvocationCountEXT must be declared as a scalar 32-bit integer value

FragSizeEXT

Decorating a variable with the FragSizeEXT built-in decoration will make that variable contain the dimensions in pixels of the area that the fragment covers for that invocation.

If fragment density map is not enabled, FragSizeEXT will be filled with a value of (1,1).

Valid Usage
  • VUID-FragSizeEXT-FragSizeEXT-04220
    The FragSizeEXT decoration must be used only within the Fragment Execution Model

  • VUID-FragSizeEXT-FragSizeEXT-04221
    The variable decorated with FragSizeEXT must be declared using the Input Storage Class

  • VUID-FragSizeEXT-FragSizeEXT-04222
    The variable decorated with FragSizeEXT must be declared as a two-component vector of 32-bit integer values

FragStencilRefEXT

Decorating a variable with the FragStencilRefEXT built-in decoration will make that variable contain the new stencil reference value for all samples covered by the fragment. This value will be used as the stencil reference value used in stencil testing.

To write to FragStencilRefEXT, a shader must declare the StencilRefReplacingEXT execution mode. If a shader declares the StencilRefReplacingEXT execution mode and there is an execution path through the shader that does not set FragStencilRefEXT, then the fragment’s stencil reference value is undefined for executions of the shader that take that path.

Only the least significant s bits of the integer value of the variable decorated with FragStencilRefEXT are considered for stencil testing, where s is the number of bits in the stencil framebuffer attachment, and higher order bits are discarded.

Valid Usage
  • VUID-FragStencilRefEXT-FragStencilRefEXT-04223
    The FragStencilRefEXT decoration must be used only within the Fragment Execution Model

  • VUID-FragStencilRefEXT-FragStencilRefEXT-04224
    The variable decorated with FragStencilRefEXT must be declared using the Output Storage Class

  • VUID-FragStencilRefEXT-FragStencilRefEXT-04225
    The variable decorated with FragStencilRefEXT must be declared as a scalar integer value

FragmentSizeNV

Decorating a variable with the FragmentSizeNV built-in decoration will make that variable contain the width and height of the fragment.

Valid Usage
  • VUID-FragmentSizeNV-FragmentSizeNV-04226
    The FragmentSizeNV decoration must be used only within the Fragment Execution Model

  • VUID-FragmentSizeNV-FragmentSizeNV-04227
    The variable decorated with FragmentSizeNV must be declared using the Input Storage Class

  • VUID-FragmentSizeNV-FragmentSizeNV-04228
    The variable decorated with FragmentSizeNV must be declared as a two-component vector of 32-bit integer values

FrontFacing

Decorating a variable with the FrontFacing built-in decoration will make that variable contain whether the fragment is front or back facing. This variable is non-zero if the current fragment is considered to be part of a front-facing polygon primitive or of a non-polygon primitive and is zero if the fragment is considered to be part of a back-facing polygon primitive.

Valid Usage
  • VUID-FrontFacing-FrontFacing-04229
    The FrontFacing decoration must be used only within the Fragment Execution Model

  • VUID-FrontFacing-FrontFacing-04230
    The variable decorated with FrontFacing must be declared using the Input Storage Class

  • VUID-FrontFacing-FrontFacing-04231
    The variable decorated with FrontFacing must be declared as a boolean value

FullyCoveredEXT

Decorating a variable with the FullyCoveredEXT built-in decoration will make that variable indicate whether the fragment area is fully covered by the generating primitive. This variable is non-zero if conservative rasterization is enabled and the current fragment area is fully covered by the generating primitive, and is zero if the fragment is not covered or partially covered, or conservative rasterization is disabled.

If the implementation supports VkPhysicalDeviceConservativeRasterizationPropertiesEXT::conservativeRasterizationPostDepthCoverage and the PostDepthCoverage execution mode is specified the SampleMask built-in input variable will reflect the coverage after the early per-fragment depth and stencil tests are applied.

Valid Usage
  • VUID-FullyCoveredEXT-FullyCoveredEXT-04232
    The FullyCoveredEXT decoration must be used only within the Fragment Execution Model

  • VUID-FullyCoveredEXT-FullyCoveredEXT-04233
    The variable decorated with FullyCoveredEXT must be declared using the Input Storage Class

  • VUID-FullyCoveredEXT-FullyCoveredEXT-04234
    The variable decorated with FullyCoveredEXT must be declared as a boolean value

  • VUID-FullyCoveredEXT-conservativeRasterizationPostDepthCoverage-04235
    If VkPhysicalDeviceConservativeRasterizationPropertiesEXT::conservativeRasterizationPostDepthCoverage is not supported the PostDepthCoverage Execution Mode must not be declared, when a variable with the FullyCoveredEXT decoration is declared

GlobalInvocationId

Decorating a variable with the GlobalInvocationId built-in decoration will make that variable contain the location of the current invocation within the global workgroup. Each component is equal to the index of the local workgroup multiplied by the size of the local workgroup plus LocalInvocationId.

Valid Usage
  • VUID-GlobalInvocationId-GlobalInvocationId-04236
    The GlobalInvocationId decoration must be used only within the GLCompute, MeshNV, or TaskNV Execution Model

  • VUID-GlobalInvocationId-GlobalInvocationId-04237
    The variable decorated with GlobalInvocationId must be declared using the Input Storage Class

  • VUID-GlobalInvocationId-GlobalInvocationId-04238
    The variable decorated with GlobalInvocationId must be declared as a three-component vector of 32-bit integer values

HelperInvocation

Decorating a variable with the HelperInvocation built-in decoration will make that variable contain whether the current invocation is a helper invocation. This variable is non-zero if the current fragment being shaded is a helper invocation and zero otherwise. A helper invocation is an invocation of the shader that is produced to satisfy internal requirements such as the generation of derivatives.

Note

It is very likely that a helper invocation will have a value of SampleMask fragment shader input value that is zero.

Valid Usage
  • VUID-HelperInvocation-HelperInvocation-04239
    The HelperInvocation decoration must be used only within the Fragment Execution Model

  • VUID-HelperInvocation-HelperInvocation-04240
    The variable decorated with HelperInvocation must be declared using the Input Storage Class

  • VUID-HelperInvocation-HelperInvocation-04241
    The variable decorated with HelperInvocation must be declared as a boolean value

HitKindKHR

A variable decorated with the HitKindKHR decoration will describe the intersection that triggered the execution of the current shader. The values are determined by the intersection shader. For user-defined intersection shaders this is the value that was passed to the “Hit Kind” operand of OpReportIntersectionKHR. For triangle intersection candidates, this will be one of HitKindFrontFacingTriangleKHR or HitKindBackFacingTriangleKHR.

Valid Usage
  • VUID-HitKindKHR-HitKindKHR-04242
    The HitKindKHR decoration must be used only within the AnyHitKHR or ClosestHitKHR Execution Model

  • VUID-HitKindKHR-HitKindKHR-04243
    The variable decorated with HitKindKHR must be declared using the Input Storage Class

  • VUID-HitKindKHR-HitKindKHR-04244
    The variable decorated with HitKindKHR must be declared as a scalar 32-bit integer value

HitTNV

A variable decorated with the HitTNV decoration is equivalent to a variable decorated with the RayTmaxKHR decoration.

Valid Usage
  • VUID-HitTNV-HitTNV-04245
    The HitTNV decoration must be used only within the AnyHitNV or ClosestHitNV Execution Model

  • VUID-HitTNV-HitTNV-04246
    The variable decorated with HitTNV must be declared using the Input Storage Class

  • VUID-HitTNV-HitTNV-04247
    The variable decorated with HitTNV must be declared as a scalar 32-bit floating-point value

IncomingRayFlagsKHR

A variable with the IncomingRayFlagsKHR decoration will contain the ray flags passed in to the trace call that invoked this particular shader.

Valid Usage
  • VUID-IncomingRayFlagsKHR-IncomingRayFlagsKHR-04248
    The IncomingRayFlagsKHR decoration must be used only within the IntersectionKHR, AnyHitKHR, ClosestHitKHR, or MissKHR Execution Model

  • VUID-IncomingRayFlagsKHR-IncomingRayFlagsKHR-04249
    The variable decorated with IncomingRayFlagsKHR must be declared using the Input Storage Class

  • VUID-IncomingRayFlagsKHR-IncomingRayFlagsKHR-04250
    The variable decorated with IncomingRayFlagsKHR must be declared as a scalar 32-bit integer value

InstanceCustomIndexKHR

A variable decorated with the InstanceCustomIndexKHR decoration will contain the application-defined value of the instance that intersects the current ray. This variable contains the value that was specified in VkAccelerationStructureInstanceKHR::instanceCustomIndex for the current acceleration structure instance in the lower 24 bits and the upper 8 bits will be zero.

Valid Usage
  • VUID-InstanceCustomIndexKHR-InstanceCustomIndexKHR-04251
    The InstanceCustomIndexKHR decoration must be used only within the IntersectionKHR, AnyHitKHR, or ClosestHitKHR Execution Model

  • VUID-InstanceCustomIndexKHR-InstanceCustomIndexKHR-04252
    The variable decorated with InstanceCustomIndexKHR must be declared using the Input Storage Class

  • VUID-InstanceCustomIndexKHR-InstanceCustomIndexKHR-04253
    The variable decorated with InstanceCustomIndexKHR must be declared as a scalar 32-bit integer value

InstanceId

Decorating a variable in an intersection, any-hit, or closest hit shader with the InstanceId decoration will make that variable contain the index of the instance that intersects the current ray.

Valid Usage
  • VUID-InstanceId-InstanceId-04254
    The InstanceId decoration must be used only within the IntersectionKHR, AnyHitKHR, or ClosestHitKHR Execution Model

  • VUID-InstanceId-InstanceId-04255
    The variable decorated with InstanceId must be declared using the Input Storage Class

  • VUID-InstanceId-InstanceId-04256
    The variable decorated with InstanceId must be declared as a scalar 32-bit integer value

InvocationId

Decorating a variable with the InvocationId built-in decoration will make that variable contain the index of the current shader invocation in a geometry shader, or the index of the output patch vertex in a tessellation control shader.

In a geometry shader, the index of the current shader invocation ranges from zero to the number of instances declared in the shader minus one. If the instance count of the geometry shader is one or is not specified, then InvocationId will be zero.

Valid Usage
  • VUID-InvocationId-InvocationId-04257
    The InvocationId decoration must be used only within the TessellationControl or Geometry Execution Model

  • VUID-InvocationId-InvocationId-04258
    The variable decorated with InvocationId must be declared using the Input Storage Class

  • VUID-InvocationId-InvocationId-04259
    The variable decorated with InvocationId must be declared as a scalar 32-bit integer value

InvocationsPerPixelNV

Decorating a variable with the InvocationsPerPixelNV built-in decoration will make that variable contain the maximum number of fragment shader invocations per pixel, as derived from the effective shading rate for the fragment. If a primitive does not fully cover a pixel, the number of fragment shader invocations for that pixel may be less than the value of InvocationsPerPixelNV. If the shading rate indicates a fragment covering multiple pixels, then InvocationsPerPixelNV will be one.

Valid Usage
  • VUID-InvocationsPerPixelNV-InvocationsPerPixelNV-04260
    The InvocationsPerPixelNV decoration must be used only within the Fragment Execution Model

  • VUID-InvocationsPerPixelNV-InvocationsPerPixelNV-04261
    The variable decorated with InvocationsPerPixelNV must be declared using the Input Storage Class

  • VUID-InvocationsPerPixelNV-InvocationsPerPixelNV-04262
    The variable decorated with InvocationsPerPixelNV must be declared as a scalar 32-bit integer value

InstanceIndex

Decorating a variable in a vertex shader with the InstanceIndex built-in decoration will make that variable contain the index of the instance that is being processed by the current vertex shader invocation. InstanceIndex begins at the firstInstance parameter to vkCmdDraw or vkCmdDrawIndexed or at the firstInstance member of a structure consumed by vkCmdDrawIndirect or vkCmdDrawIndexedIndirect.

Valid Usage
  • VUID-InstanceIndex-InstanceIndex-04263
    The InstanceIndex decoration must be used only within the Vertex Execution Model

  • VUID-InstanceIndex-InstanceIndex-04264
    The variable decorated with InstanceIndex must be declared using the Input Storage Class

  • VUID-InstanceIndex-InstanceIndex-04265
    The variable decorated with InstanceIndex must be declared as a scalar 32-bit integer value

LaunchIDKHR

A variable decorated with the LaunchIDKHR decoration will specify the index of the work item being process. One work item is generated for each of the width × height × depth items dispatched by a vkCmdTraceRaysKHR command. All shader invocations inherit the same value for variables decorated with LaunchIDKHR.

Valid Usage
  • VUID-LaunchIDKHR-LaunchIDKHR-04266
    The LaunchIDKHR decoration must be used only within the RayGenerationKHR, IntersectionKHR, AnyHitKHR, ClosestHitKHR, or MissKHR Execution Model

  • VUID-LaunchIDKHR-LaunchIDKHR-04267
    The variable decorated with LaunchIDKHR must be declared using the Input Storage Class

  • VUID-LaunchIDKHR-LaunchIDKHR-04268
    The variable decorated with LaunchIDKHR must be declared as a three-component vector of 32-bit integer values

LaunchSizeKHR

A variable decorated with the LaunchSizeKHR decoration will contain the width, height, and depth dimensions passed to the vkCmdTraceRaysKHR command that initiated this shader execution. The width is in the first component, the height is in the second component, and the depth is in the third component.

Valid Usage
  • VUID-LaunchSizeKHR-LaunchSizeKHR-04269
    The LaunchSizeKHR decoration must be used only within the RayGenerationKHR, IntersectionKHR, AnyHitKHR, ClosestHitKHR, or MissKHR Execution Model

  • VUID-LaunchSizeKHR-LaunchSizeKHR-04270
    The variable decorated with LaunchSizeKHR must be declared using the Input Storage Class

  • VUID-LaunchSizeKHR-LaunchSizeKHR-04271
    The variable decorated with LaunchSizeKHR must be declared as a three-component vector of 32-bit integer values

Layer

Decorating a variable with the Layer built-in decoration will make that variable contain the select layer of a multi-layer framebuffer attachment.

In a mesh, vertex, tessellation evaluation, or geometry shader, any variable decorated with Layer can be written with the framebuffer layer index to which the primitive produced by that shader will be directed.

The last active vertex processing stage (in pipeline order) controls the Layer that is used. Outputs in previous shader stages are not used, even if the last stage fails to write the Layer.

If the last active vertex processing stage shader entry point’s interface does not include a variable decorated with Layer, then the first layer is used. If a vertex processing stage shader entry point’s interface includes a variable decorated with Layer, it must write the same value to Layer for all output vertices of a given primitive. If the Layer value is less than 0 or greater than or equal to the number of layers in the framebuffer, then primitives may still be rasterized, fragment shaders may be executed, and the framebuffer values for all layers are undefined.

If a variable with the Layer decoration is also decorated with ViewportRelativeNV, then the ViewportIndex is added to the layer that is used for rendering and that is made available in the fragment shader. If the shader writes to a variable decorated ViewportMaskNV, then the layer selected has a different value for each viewport a primitive is rendered to.

In a fragment shader, a variable decorated with Layer contains the layer index of the primitive that the fragment invocation belongs to.

Valid Usage
  • VUID-Layer-Layer-04272
    The Layer decoration must be used only within the MeshNV, Vertex, TessellationEvaluation, Geometry, or Fragment Execution Model

  • VUID-Layer-Layer-04273
    If the shaderOutputLayer feature is not enabled then the Layer decoration must be used only within the Geometry or Fragment Execution Model

  • VUID-Layer-Layer-04274
    The variable decorated with Layer within the MeshNV, Vertex, TessellationEvaluation, or Geometry Execution Model must be declared using the Output Storage Class

  • VUID-Layer-Layer-04275
    The variable decorated with Layer within the Fragment Execution Model must be declared using the Input Storage Class

  • VUID-Layer-Layer-04276
    The variable decorated with Layer must be declared as a scalar 32-bit integer value

LayerPerViewNV

Decorating a variable with the LayerPerViewNV built-in decoration will make that variable contain the per-view layer information. The per-view layer has the same semantics as Layer, for each view.

Valid Usage
  • VUID-LayerPerViewNV-LayerPerViewNV-04277
    The LayerPerViewNV decoration must be used only within the MeshNV Execution Model

  • VUID-LayerPerViewNV-LayerPerViewNV-04278
    The variable decorated with LayerPerViewNV must be declared using the Output Storage Class

  • VUID-LayerPerViewNV-LayerPerViewNV-04279
    The variable decorated with LayerPerViewNV must also be decorated with the PerViewNV decoration.

  • VUID-LayerPerViewNV-LayerPerViewNV-04280
    The variable decorated with LayerPerViewNV must be declared as an array of scalar 32-bit integer values

LocalInvocationId

Decorating a variable with the LocalInvocationId built-in decoration will make that variable contain the location of the current task, mesh, or compute shader invocation within the local workgroup. Each component ranges from zero through to the size of the workgroup in that dimension minus one.

Note

If the size of the workgroup in a particular dimension is one, then the LocalInvocationId in that dimension will be zero. If the workgroup is effectively two-dimensional, then LocalInvocationId.z will be zero. If the workgroup is effectively one-dimensional, then both LocalInvocationId.y and LocalInvocationId.z will be zero.

Valid Usage
  • VUID-LocalInvocationId-LocalInvocationId-04281
    The LocalInvocationId decoration must be used only within the GLCompute, MeshNV, or TaskNV Execution Model

  • VUID-LocalInvocationId-LocalInvocationId-04282
    The variable decorated with LocalInvocationId must be declared using the Input Storage Class

  • VUID-LocalInvocationId-LocalInvocationId-04283
    The variable decorated with LocalInvocationId must be declared as a three-component vector of 32-bit integer values

LocalInvocationIndex

Decorating a variable with the LocalInvocationIndex built-in decoration will make that variable contain a one-dimensional representation of LocalInvocationId. This is computed as:

LocalInvocationIndex =
    LocalInvocationId.z * WorkgroupSize.x * WorkgroupSize.y +
    LocalInvocationId.y * WorkgroupSize.x +
    LocalInvocationId.x;
Valid Usage
  • VUID-LocalInvocationIndex-LocalInvocationIndex-04284
    The LocalInvocationIndex decoration must be used only within the GLCompute, MeshNV, or TaskNV Execution Model

  • VUID-LocalInvocationIndex-LocalInvocationIndex-04285
    The variable decorated with LocalInvocationIndex must be declared using the Input Storage Class

  • VUID-LocalInvocationIndex-LocalInvocationIndex-04286
    The variable decorated with LocalInvocationIndex must be declared as a scalar 32-bit integer value

MeshViewCountNV

Decorating a variable with the MeshViewCountNV built-in decoration will make that variable contain the number of views processed by the current mesh or task shader invocations.

Valid Usage
  • VUID-MeshViewCountNV-MeshViewCountNV-04287
    The MeshViewCountNV decoration must be used only within the MeshNV or TaskNV Execution Model

  • VUID-MeshViewCountNV-MeshViewCountNV-04288
    The variable decorated with MeshViewCountNV must be declared using the Input Storage Class

  • VUID-MeshViewCountNV-MeshViewCountNV-04289
    The variable decorated with MeshViewCountNV must be declared as a scalar 32-bit integer value

MeshViewIndicesNV

Decorating a variable with the MeshViewIndicesNV built-in decoration will make that variable contain the mesh view indices. The mesh view indices is an array of values where each element holds the view number of one of the views being processed by the current mesh or task shader invocations. The values of array elements with indices great than or equal to MeshViewCountNV are undefined. If the value of MeshViewIndicesNV[i] is j, then any outputs decorated with PerViewNV will take on the value of array element i when processing primitives for view index j.

Valid Usage
  • VUID-MeshViewIndicesNV-MeshViewIndicesNV-04290
    The MeshViewIndicesNV decoration must be used only within the MeshNV or TaskNV Execution Model

  • VUID-MeshViewIndicesNV-MeshViewIndicesNV-04291
    The variable decorated with MeshViewIndicesNV must be declared using the Input Storage Class

  • VUID-MeshViewIndicesNV-MeshViewIndicesNV-04292
    The variable decorated with MeshViewIndicesNV must be declared as an array of scalar 32-bit integer values

NumSubgroups

Decorating a variable with the NumSubgroups built-in decoration will make that variable contain the number of subgroups in the local workgroup.

Valid Usage
  • VUID-NumSubgroups-NumSubgroups-04293
    The NumSubgroups decoration must be used only within the GLCompute, MeshNV, or TaskNV Execution Model

  • VUID-NumSubgroups-NumSubgroups-04294
    The variable decorated with NumSubgroups must be declared using the Input Storage Class

  • VUID-NumSubgroups-NumSubgroups-04295
    The variable decorated with NumSubgroups must be declared as a scalar 32-bit integer value

NumWorkgroups

Decorating a variable with the NumWorkgroups built-in decoration will make that variable contain the number of local workgroups that are part of the dispatch that the invocation belongs to. Each component is equal to the values of the workgroup count parameters passed into the dispatch commands.

Valid Usage
  • VUID-NumWorkgroups-NumWorkgroups-04296
    The NumWorkgroups decoration must be used only within the GLCompute Execution Model

  • VUID-NumWorkgroups-NumWorkgroups-04297
    The variable decorated with NumWorkgroups must be declared using the Input Storage Class

  • VUID-NumWorkgroups-NumWorkgroups-04298
    The variable decorated with NumWorkgroups must be declared as a three-component vector of 32-bit integer values

ObjectRayDirectionKHR

A variable decorated with the ObjectRayDirectionKHR decoration will specify the direction of the ray being processed, in object space.

Valid Usage
  • VUID-ObjectRayDirectionKHR-ObjectRayDirectionKHR-04299
    The ObjectRayDirectionKHR decoration must be used only within the IntersectionKHR, AnyHitKHR, or ClosestHitKHR Execution Model

  • VUID-ObjectRayDirectionKHR-ObjectRayDirectionKHR-04300
    The variable decorated with ObjectRayDirectionKHR must be declared using the Input Storage Class

  • VUID-ObjectRayDirectionKHR-ObjectRayDirectionKHR-04301
    The variable decorated with ObjectRayDirectionKHR must be declared as a three-component vector of 32-bit floating-point values

ObjectRayOriginKHR

A variable decorated with the ObjectRayOriginKHR decoration will specify the origin of the ray being processed, in object space.

Valid Usage
  • VUID-ObjectRayOriginKHR-ObjectRayOriginKHR-04302
    The ObjectRayOriginKHR decoration must be used only within the IntersectionKHR, AnyHitKHR, or ClosestHitKHR Execution Model

  • VUID-ObjectRayOriginKHR-ObjectRayOriginKHR-04303
    The variable decorated with ObjectRayOriginKHR must be declared using the Input Storage Class

  • VUID-ObjectRayOriginKHR-ObjectRayOriginKHR-04304
    The variable decorated with ObjectRayOriginKHR must be declared as a three-component vector of 32-bit floating-point values

ObjectToWorldKHR

A variable decorated with the ObjectToWorldKHR decoration will contain the current object-to-world transformation matrix, which is determined by the instance of the current intersection.

Valid Usage
  • VUID-ObjectToWorldKHR-ObjectToWorldKHR-04305
    The ObjectToWorldKHR decoration must be used only within the IntersectionKHR, AnyHitKHR, or ClosestHitKHR Execution Model

  • VUID-ObjectToWorldKHR-ObjectToWorldKHR-04306
    The variable decorated with ObjectToWorldKHR must be declared using the Input Storage Class

  • VUID-ObjectToWorldKHR-ObjectToWorldKHR-04307
    The variable decorated with ObjectToWorldKHR must be declared as a matrix with four columns of three-component vectors of 32-bit floating-point values

PatchVertices

Decorating a variable with the PatchVertices built-in decoration will make that variable contain the number of vertices in the input patch being processed by the shader. A single tessellation control or tessellation evaluation shader can read patches of differing sizes, so the value of the PatchVertices variable may differ between patches.

Valid Usage
  • VUID-PatchVertices-PatchVertices-04308
    The PatchVertices decoration must be used only within the TessellationControl or TessellationEvaluation Execution Model

  • VUID-PatchVertices-PatchVertices-04309
    The variable decorated with PatchVertices must be declared using the Input Storage Class

  • VUID-PatchVertices-PatchVertices-04310
    The variable decorated with PatchVertices must be declared as a scalar 32-bit integer value

PointCoord

Decorating a variable with the PointCoord built-in decoration will make that variable contain the coordinate of the current fragment within the point being rasterized, normalized to the size of the point with origin in the upper left corner of the point, as described in Basic Point Rasterization. If the primitive the fragment shader invocation belongs to is not a point, then the variable decorated with PointCoord contains an undefined value.

Note

Depending on how the point is rasterized, PointCoord may never reach (0,0) or (1,1).

Valid Usage
  • VUID-PointCoord-PointCoord-04311
    The PointCoord decoration must be used only within the Fragment Execution Model

  • VUID-PointCoord-PointCoord-04312
    The variable decorated with PointCoord must be declared using the Input Storage Class

  • VUID-PointCoord-PointCoord-04313
    The variable decorated with PointCoord must be declared as a two-component vector of 32-bit floating-point values

PointSize

Decorating a variable with the PointSize built-in decoration will make that variable contain the size of point primitives. The value written to the variable decorated with PointSize by the last vertex processing stage in the pipeline is used as the framebuffer-space size of points produced by rasterization.

Note

When PointSize decorates a variable in the Input Storage Class, it contains the data written to the output variable decorated with PointSize from the previous shader stage.

Valid Usage
  • VUID-PointSize-PointSize-04314
    The PointSize decoration must be used only within the MeshNV, Vertex, TessellationControl, TessellationEvaluation, or Geometry Execution Model

  • VUID-PointSize-PointSize-04315
    The variable decorated with PointSize within the MeshNV or Vertex Execution Model must be declared using the Output Storage Class

  • VUID-PointSize-PointSize-04316
    The variable decorated with PointSize within the TessellationControl, TessellationEvaluation, or Geometry Execution Model must not be declared using a Storage Class other than Input or Output

  • VUID-PointSize-PointSize-04317
    The variable decorated with PointSize must be declared as a scalar 32-bit floating-point value

Position

Decorating a variable with the Position built-in decoration will make that variable contain the position of the current vertex. In the last vertex processing stage, the value of the variable decorated with Position is used in subsequent primitive assembly, clipping, and rasterization operations.

Note

When Position decorates a variable in the Input Storage Class, it contains the data written to the output variable decorated with Position from the previous shader stage.

Valid Usage
  • VUID-Position-Position-04318
    The Position decoration must be used only within the MeshNV, Vertex, TessellationControl, TessellationEvaluation, or Geometry Execution Model

  • VUID-Position-Position-04319
    The variable decorated with Position within MeshNV or Vertex Execution Model must be declared using the Output Storage Class

  • VUID-Position-Position-04320
    The variable decorated with Position within TessellationControl, TessellationEvaluation, or Geometry Execution Model must not be declared using a Storage Class other than Input or Output

  • VUID-Position-Position-04321
    The variable decorated with Position must be declared as a four-component vector of 32-bit floating-point values

PositionPerViewNV

Decorating a variable with the PositionPerViewNV built-in decoration will make that variable contain the position of the current vertex, for each view.

Elements of the array correspond to views in a multiview subpass, and those elements corresponding to views in the view mask of the subpass the shader is compiled against will be used as the position value for those views. For the final vertex processing stage in the pipeline, values written to an output variable decorated with PositionPerViewNV are used in subsequent primitive assembly, clipping, and rasterization operations, as with Position. PositionPerViewNV output in an earlier vertex processing stage is available as an input in the subsequent vertex processing stage.

If a shader is compiled against a subpass that has the VK_SUBPASS_DESCRIPTION_PER_VIEW_POSITION_X_ONLY_BIT_NVX bit set, then the position values for each view must not differ in any component other than the X component. If the values do differ, one will be chosen in an implementation-dependent manner.

Valid Usage
  • VUID-PositionPerViewNV-PositionPerViewNV-04322
    The PositionPerViewNV decoration must be used only within the MeshNV, Vertex, TessellationControl, TessellationEvaluation, or Geometry Execution Model

  • VUID-PositionPerViewNV-PositionPerViewNV-04323
    The variable decorated with PositionPerViewNV within the Vertex, or MeshNV Execution Model must be declared using the Output Storage Class

  • VUID-PositionPerViewNV-PositionPerViewNV-04324
    The variable decorated with PositionPerViewNV within the TessellationControl, TessellationEvaluation, or Geometry Execution Model must not be declared using a Storage Class other than Input or Output

  • VUID-PositionPerViewNV-PositionPerViewNV-04325
    The variable decorated with PositionPerViewNV must be declared as an array of four-component vector of 32-bit floating-point values with at least as many elements as the maximum view in the subpass’s view mask plus one

  • VUID-PositionPerViewNV-PositionPerViewNV-04326
    The array variable decorated with PositionPerViewNV must only be indexed by a constant or specialization constant

PrimitiveCountNV

Decorating a variable with the PrimitiveCountNV decoration will make that variable contain the primitive count. The primitive count specifies the number of primitives in the output mesh produced by the mesh shader that will be processed by subsequent pipeline stages.

Valid Usage
  • VUID-PrimitiveCountNV-PrimitiveCountNV-04327
    The PrimitiveCountNV decoration must be used only within the MeshNV Execution Model

  • VUID-PrimitiveCountNV-PrimitiveCountNV-04328
    The variable decorated with PrimitiveCountNV must be declared using the Output Storage Class

  • VUID-PrimitiveCountNV-PrimitiveCountNV-04329
    The variable decorated with PrimitiveCountNV must be declared as a scalar 32-bit integer value

PrimitiveId

Decorating a variable with the PrimitiveId built-in decoration will make that variable contain the index of the current primitive.

The index of the first primitive generated by a drawing command is zero, and the index is incremented after every individual point, line, or triangle primitive is processed.

For triangles drawn as points or line segments (see Polygon Mode), the primitive index is incremented only once, even if multiple points or lines are eventually drawn.

Variables decorated with PrimitiveId are reset to zero between each instance drawn.

Restarting a primitive topology using primitive restart has no effect on the value of variables decorated with PrimitiveId.

In tessellation control and tessellation evaluation shaders, it will contain the index of the patch within the current set of rendering primitives that correspond to the shader invocation.

In a geometry shader, it will contain the number of primitives presented as input to the shader since the current set of rendering primitives was started.

In a fragment shader, it will contain the primitive index written by the geometry shader if a geometry shader is present, or with the value that would have been presented as input to the geometry shader had it been present.

In an intersection, any-hit, or closest hit shader, it will contain the index within the geometry of the triangle or bounding box being processed.

Note

When the PrimitiveId decoration is applied to an output variable in the mesh shader or geometry shader, the resulting value is seen through the PrimitiveId decorated input variable in the fragment shader.

The fragment shader using PrimitiveId will need to declare either the Geometry or Tessellation capability to satisfy the requirement SPIR-V has to use PrimitiveId.

Valid Usage
  • VUID-PrimitiveId-PrimitiveId-04330
    The PrimitiveId decoration must be used only within the MeshNV, IntersectionKHR, AnyHitKHR, ClosestHitKHR, TessellationControl, TessellationEvaluation, Geometry, or Fragment Execution Model

  • VUID-PrimitiveId-Fragment-04331
    If pipeline contains both the Fragment and Geometry Execution Model and a variable decorated with PrimitiveId is read from Fragment shader, then the Geometry shader must write to the output variables decorated with PrimitiveId in all execution paths

  • VUID-PrimitiveId-Fragment-04332
    If pipeline contains both the Fragment and MeshNV Execution Model and a variable decorated with PrimitiveId is read from Fragment shader, then the MeshNV shader must write to the output variables decorated with PrimitiveId in all execution paths

  • VUID-PrimitiveId-Fragment-04333
    If Fragment Execution Model contains a variable decorated with PrimitiveId either the Geometry or Tessellation capability must also be declared

  • VUID-PrimitiveId-PrimitiveId-04334
    The variable decorated with PrimitiveId within the TessellationControl, TessellationEvaluation, Fragment, IntersectionKHR, AnyHitKHR, or ClosestHitKHR Execution Model must be declared using the Input Storage Class

  • VUID-PrimitiveId-PrimitiveId-04335
    The variable decorated with PrimitiveId within the Geometry Execution Model must be declared using the Input or Output Storage Class

  • VUID-PrimitiveId-PrimitiveId-04336
    The variable decorated with PrimitiveId within the MeshNV Execution Model must be declared using the Output Storage Class

  • VUID-PrimitiveId-PrimitiveId-04337
    The variable decorated with PrimitiveId must be declared as a scalar 32-bit integer value

PrimitiveIndicesNV

Decorating a variable with the PrimitiveIndicesNV decoration will make that variable contain the output array of vertex index values. Depending on the output primitive type declared using the execution mode, the indices are split into groups of one (OutputPoints), two (OutputLinesNV), or three (OutputTriangles) indices and each group generates a primitive.

Valid Usage
  • VUID-PrimitiveIndicesNV-PrimitiveIndicesNV-04338
    The PrimitiveIndicesNV decoration must be used only within the MeshNV Execution Model

  • VUID-PrimitiveIndicesNV-PrimitiveIndicesNV-04339
    The variable decorated with PrimitiveIndicesNV must be declared using the Output Storage Class

  • VUID-PrimitiveIndicesNV-PrimitiveIndicesNV-04340
    The variable decorated with PrimitiveIndicesNV must be declared as an array of scalar 32-bit integer values

  • VUID-PrimitiveIndicesNV-PrimitiveIndicesNV-04341
    All index values of the array decorated with PrimitiveIndicesNV must be in the range [0, N-1], where N is the value specified by the OutputVertices Execution Mode

  • VUID-PrimitiveIndicesNV-OutputPoints-04342
    If the Execution Mode is OutputPoints, then the array decorated with PrimitiveIndicesNV must be the size of the value specified by OutputPrimitivesNV

  • VUID-PrimitiveIndicesNV-OutputLinesNV-04343
    If the Execution Mode is OutputLinesNV, then the array decorated with PrimitiveIndicesNV must be the size of two times the value specified by OutputPrimitivesNV

  • VUID-PrimitiveIndicesNV-OutputTrianglesNV-04344
    If the Execution Mode is OutputTrianglesNV, then the array decorated with PrimitiveIndicesNV must be the size of three times the value specified by OutputPrimitivesNV

PrimitiveShadingRateKHR

Decorating a variable with the PrimitiveShadingRateKHR built-in decoration will make that variable contain the primitive fragment shading rate.

The value written to the variable decorated with PrimitiveShadingRateKHR by the last vertex processing stage in the pipeline is used as the primitive fragment shading rate. Outputs in previous shader stages are ignored.

If the last active vertex processing stage shader entry point’s interface does not include a variable decorated with PrimitiveShadingRateKHR, then it is as if the shader specified a fragment shading rate value of 0, indicating a horizontal and vertical rate of 1 pixel.

If a shader has PrimitiveShadingRateKHR in the output interface and there is an execution path through the shader that does not write to it, its value is undefined for executions of the shader that take that path.

Valid Usage
  • VUID-PrimitiveShadingRateKHR-PrimitiveShadingRateKHR-04484
    The PrimitiveShadingRateKHR decoration must be used only within the MeshNV, Vertex, or Geometry Execution Model

  • VUID-PrimitiveShadingRateKHR-PrimitiveShadingRateKHR-04485
    The variable decorated with PrimitiveShadingRateKHR must be declared using the Output Storage Class

  • VUID-PrimitiveShadingRateKHR-PrimitiveShadingRateKHR-04486
    The variable decorated with PrimitiveShadingRateKHR must be declared as a scalar 32-bit integer value

  • VUID-PrimitiveShadingRateKHR-PrimitiveShadingRateKHR-04487
    The value written to PrimitiveShadingRateKHR must include no more than one of Vertical2Pixels and Vertical4Pixels

  • VUID-PrimitiveShadingRateKHR-PrimitiveShadingRateKHR-04488
    The value written to PrimitiveShadingRateKHR must include no more than one of Horizontal2Pixels and Horizontal4Pixels

  • VUID-PrimitiveShadingRateKHR-PrimitiveShadingRateKHR-04489
    The value written to PrimitiveShadingRateKHR must not have any bits set other than those defined by Fragment Shading Rate Flags enumerants in the SPIR-V specification

RayGeometryIndexKHR

A variable decorated with the RayGeometryIndexKHR decoration will contain the geometry index for the acceleration structure geometry currently being shaded.

Valid Usage
  • VUID-RayGeometryIndexKHR-RayGeometryIndexKHR-04345
    The RayGeometryIndexKHR decoration must be used only within the IntersectionKHR, AnyHitKHR, or ClosestHitKHR Execution Model

  • VUID-RayGeometryIndexKHR-RayGeometryIndexKHR-04346
    The variable decorated with RayGeometryIndexKHR must be declared using the Input Storage Class

  • VUID-RayGeometryIndexKHR-RayGeometryIndexKHR-04347
    The variable decorated with RayGeometryIndexKHR must be declared as a scalar 32-bit integer value

RayTmaxKHR

A variable decorated with the RayTmaxKHR decoration will contain the parametric tmax values of the ray being processed. The values are independent of the space in which the ray origin and direction exist.

The tmax value changes throughout the lifetime of the ray query that produced the intersection. In the closest hit shader, the value reflects the closest distance to the intersected primitive. In the any-hit shader, it reflects the distance to the primitive currently being intersected. In the intersection shader, it reflects the distance to the closest primitive intersected so far. The value can change in the intersection shader after calling OpReportIntersectionKHR if the corresponding any-hit shader does not ignore the intersection. In a miss shader, the value is identical to the parameter passed into OpTraceRayKHR.

Valid Usage
  • VUID-RayTmaxKHR-RayTmaxKHR-04348
    The RayTmaxKHR decoration must be used only within the IntersectionKHR, AnyHitKHR, ClosestHitKHR, or MissKHR Execution Model

  • VUID-RayTmaxKHR-RayTmaxKHR-04349
    The variable decorated with RayTmaxKHR must be declared using the Input Storage Class

  • VUID-RayTmaxKHR-RayTmaxKHR-04350
    The variable decorated with RayTmaxKHR must be declared as a scalar 32-bit floating-point value

RayTminKHR

A variable decorated with the RayTminKHR decoration will contain the parametric tmin values of the ray being processed. The values are independent of the space in which the ray origin and direction exist.

The tmin value remains constant for the duration of the ray query.

Valid Usage
  • VUID-RayTminKHR-RayTminKHR-04351
    The RayTminKHR decoration must be used only within the IntersectionKHR, AnyHitKHR, ClosestHitKHR, or MissKHR Execution Model

  • VUID-RayTminKHR-RayTminKHR-04352
    The variable decorated with RayTminKHR must be declared using the Input Storage Class

  • VUID-RayTminKHR-RayTminKHR-04353
    The variable decorated with RayTminKHR must be declared as a scalar 32-bit floating-point value

SampleId

Decorating a variable with the SampleId built-in decoration will make that variable contain the coverage index for the current fragment shader invocation. SampleId ranges from zero to the number of samples in the framebuffer minus one. If a fragment shader entry point’s interface includes an input variable decorated with SampleId, Sample Shading is considered enabled with a minSampleShading value of 1.0.

Valid Usage
  • VUID-SampleId-SampleId-04354
    The SampleId decoration must be used only within the Fragment Execution Model

  • VUID-SampleId-SampleId-04355
    The variable decorated with SampleId must be declared using the Input Storage Class

  • VUID-SampleId-SampleId-04356
    The variable decorated with SampleId must be declared as a scalar 32-bit integer value

SampleMask

Decorating a variable with the SampleMask built-in decoration will make any variable contain the coverage mask for the current fragment shader invocation.

A variable in the Input storage class decorated with SampleMask will contain a bitmask of the set of samples covered by the primitive generating the fragment during rasterization. It has a sample bit set if and only if the sample is considered covered for this fragment shader invocation. SampleMask[] is an array of integers. Bits are mapped to samples in a manner where bit B of mask M (SampleMask[M]) corresponds to sample 32 × M + B.

When state specifies multiple fragment shader invocations for a given fragment, the sample mask for any single fragment shader invocation specifies the subset of the covered samples for the fragment that correspond to the invocation. In this case, the bit corresponding to each covered sample will be set in exactly one fragment shader invocation.

If the PostDepthCoverage execution mode is specified, the sample is considered covered if and only if the sample is covered by the primitive, and the sample is still covered after depth testing. Otherwise the sample is considered covered if the sample is covered by the primitive, regardless of the result of the fragment tests.

A variable in the Output storage class decorated with SampleMask is an array of integers forming a bit array in a manner similar an input variable decorated with SampleMask, but where each bit represents coverage as computed by the shader. Modifying the sample mask by writing zero to a bit of SampleMask causes the sample to be considered uncovered. If this variable is also decorated with OverrideCoverageNV, the fragment coverage is replaced with the sample mask bits set in the shader otherwise the fragment coverage is ANDed with the bits of the sample mask. If the fragment shader is being evaluated at any frequency other than per-fragment, bits of the sample mask not corresponding to the current fragment shader invocation are ignored. This array must be sized in the fragment shader either implicitly or explicitly, to be no larger than the implementation-dependent maximum sample-mask (as an array of 32-bit elements), determined by the maximum number of samples. If a fragment shader entry point’s interface includes an output variable decorated with SampleMask, the sample mask will be undefined for any array elements of any fragment shader invocations that fail to assign a value. If a fragment shader entry point’s interface does not include an output variable decorated with SampleMask, the sample mask has no effect on the processing of a fragment.

Valid Usage
  • VUID-SampleMask-SampleMask-04357
    The SampleMask decoration must be used only within the Fragment Execution Model

  • VUID-SampleMask-SampleMask-04358
    The variable decorated with SampleMask must be declared using the Input or Output Storage Class

  • VUID-SampleMask-SampleMask-04359
    The variable decorated with SampleMask must be declared as an array of 32-bit integer values

SamplePosition

Decorating a variable with the SamplePosition built-in decoration will make that variable contain the sub-pixel position of the sample being shaded. The top left of the pixel is considered to be at coordinate (0,0) and the bottom right of the pixel is considered to be at coordinate (1,1).

If the render pass has a fragment density map attachment, the variable will instead contain the sub-fragment position of the sample being shaded. The top left of the fragment is considered to be at coordinate (0,0) and the bottom right of the fragment is considered to be at coordinate (1,1) for any fragment area.

If a fragment shader entry point’s interface includes an input variable decorated with SamplePosition, Sample Shading is considered enabled with a minSampleShading value of 1.0.

If the current pipeline uses custom sample locations the value of any variable decorated with the SamplePosition built-in decoration is undefined.

Valid Usage
  • VUID-SamplePosition-SamplePosition-04360
    The SamplePosition decoration must be used only within the Fragment Execution Model

  • VUID-SamplePosition-SamplePosition-04361
    The variable decorated with SamplePosition must be declared using the Input Storage Class

  • VUID-SamplePosition-SamplePosition-04362
    The variable decorated with SamplePosition must be declared as a two-component vector of 32-bit floating-point values

ShadingRateKHR

Decorating a variable with the ShadingRateKHR built-in decoration will make that variable contain the fragment shading rate for the current fragment invocation.

Valid Usage
  • VUID-ShadingRateKHR-ShadingRateKHR-04490
    The ShadingRateKHR decoration must be used only within the Fragment Execution Model

  • VUID-ShadingRateKHR-ShadingRateKHR-04491
    The variable decorated with ShadingRateKHR must be declared using the Input Storage Class

  • VUID-ShadingRateKHR-ShadingRateKHR-04492
    The variable decorated with ShadingRateKHR must be declared as a scalar 32-bit integer value

SMCountNV

Decorating a variable with the SMCountNV built-in decoration will make that variable contain the number of SMs on the device.

Valid Usage
  • VUID-SMCountNV-SMCountNV-04363
    The variable decorated with SMCountNV must be declared using the Input Storage Class

  • VUID-SMCountNV-SMCountNV-04364
    The variable decorated with SMCountNV must be declared as a scalar 32-bit integer value

SMIDNV

Decorating a variable with the SMIDNV built-in decoration will make that variable contain the ID of the SM on which the current shader invocation is running. This variable is in the range [0, SMCountNV-1].

Valid Usage
  • VUID-SMIDNV-SMIDNV-04365
    The variable decorated with SMIDNV must be declared using the Input Storage Class

  • VUID-SMIDNV-SMIDNV-04366
    The variable decorated with SMIDNV must be declared as a scalar 32-bit integer value

SubgroupId

Decorating a variable with the SubgroupId built-in decoration will make that variable contain the index of the subgroup within the local workgroup. This variable is in range [0, NumSubgroups-1].

Valid Usage
  • VUID-SubgroupId-SubgroupId-04367
    The SubgroupId decoration must be used only within the GLCompute, MeshNV, or TaskNV Execution Model

  • VUID-SubgroupId-SubgroupId-04368
    The variable decorated with SubgroupId must be declared using the Input Storage Class

  • VUID-SubgroupId-SubgroupId-04369
    The variable decorated with SubgroupId must be declared as a scalar 32-bit integer value

SubgroupEqMask

Decorating a variable with the SubgroupEqMask builtin decoration will make that variable contain the subgroup mask of the current subgroup invocation. The bit corresponding to the SubgroupLocalInvocationId is set in the variable decorated with SubgroupEqMask. All other bits are set to zero.

SubgroupEqMaskKHR is an alias of SubgroupEqMask.

Valid Usage
  • VUID-SubgroupEqMask-SubgroupEqMask-04370
    The variable decorated with SubgroupEqMask must be declared using the Input Storage Class

  • VUID-SubgroupEqMask-SubgroupEqMask-04371
    The variable decorated with SubgroupEqMask must be declared as a four-component vector of 32-bit integer values

SubgroupGeMask

Decorating a variable with the SubgroupGeMask builtin decoration will make that variable contain the subgroup mask of the current subgroup invocation. The bits corresponding to the invocations greater than or equal to SubgroupLocalInvocationId through SubgroupSize-1 are set in the variable decorated with SubgroupGeMask. All other bits are set to zero.

SubgroupGeMaskKHR is an alias of SubgroupGeMask.

Valid Usage
  • VUID-SubgroupGeMask-SubgroupGeMask-04372
    The variable decorated with SubgroupGeMask must be declared using the Input Storage Class

  • VUID-SubgroupGeMask-SubgroupGeMask-04373
    The variable decorated with SubgroupGeMask must be declared as a four-component vector of 32-bit integer values

SubgroupGtMask

Decorating a variable with the SubgroupGtMask builtin decoration will make that variable contain the subgroup mask of the current subgroup invocation. The bits corresponding to the invocations greater than SubgroupLocalInvocationId through SubgroupSize-1 are set in the variable decorated with SubgroupGtMask. All other bits are set to zero.

SubgroupGtMaskKHR is an alias of SubgroupGtMask.

Valid Usage
  • VUID-SubgroupGtMask-SubgroupGtMask-04374
    The variable decorated with SubgroupGtMask must be declared using the Input Storage Class

  • VUID-SubgroupGtMask-SubgroupGtMask-04375
    The variable decorated with SubgroupGtMask must be declared as a four-component vector of 32-bit integer values

SubgroupLeMask

Decorating a variable with the SubgroupLeMask builtin decoration will make that variable contain the subgroup mask of the current subgroup invocation. The bits corresponding to the invocations less than or equal to SubgroupLocalInvocationId are set in the variable decorated with SubgroupLeMask. All other bits are set to zero.

SubgroupLeMaskKHR is an alias of SubgroupLeMask.

Valid Usage
  • VUID-SubgroupLeMask-SubgroupLeMask-04376
    The variable decorated with SubgroupLeMask must be declared using the Input Storage Class

  • VUID-SubgroupLeMask-SubgroupLeMask-04377
    The variable decorated with SubgroupLeMask must be declared as a four-component vector of 32-bit integer values

SubgroupLtMask

Decorating a variable with the SubgroupLtMask builtin decoration will make that variable contain the subgroup mask of the current subgroup invocation. The bits corresponding to the invocations less than SubgroupLocalInvocationId are set in the variable decorated with SubgroupLtMask. All other bits are set to zero.

SubgroupLtMaskKHR is an alias of SubgroupLtMask.

Valid Usage
  • VUID-SubgroupLtMask-SubgroupLtMask-04378
    The variable decorated with SubgroupLtMask must be declared using the Input Storage Class

  • VUID-SubgroupLtMask-SubgroupLtMask-04379
    The variable decorated with SubgroupLtMask must be declared as a four-component vector of 32-bit integer values

SubgroupLocalInvocationId

Decorating a variable with the SubgroupLocalInvocationId builtin decoration will make that variable contain the index of the invocation within the subgroup. This variable is in range [0,SubgroupSize-1].

Note

There is no direct relationship between SubgroupLocalInvocationId and LocalInvocationId or LocalInvocationIndex. If the pipeline was created with VK_PIPELINE_SHADER_STAGE_CREATE_REQUIRE_FULL_SUBGROUPS_BIT_EXT, applications can compute their own local invocation index to serve the same purpose:

index = SubgroupLocalInvocationId + SubgroupId * SubgroupSize

If full subgroups are not enabled, some subgroups may be dispatched with inactive invocations that don’t correspond to a local workgroup invocation, making the value of index unreliable.

Valid Usage
  • VUID-SubgroupLocalInvocationId-SubgroupLocalInvocationId-04380
    The variable decorated with SubgroupLocalInvocationId must be declared using the Input Storage Class

  • VUID-SubgroupLocalInvocationId-SubgroupLocalInvocationId-04381
    The variable decorated with SubgroupLocalInvocationId must be declared as a scalar 32-bit integer value

SubgroupSize

Decorating a variable with the SubgroupSize builtin decoration will make that variable contain the implementation-dependent number of invocations in a subgroup. This value must be a power-of-two integer.

If the pipeline was created with the VK_PIPELINE_SHADER_STAGE_CREATE_ALLOW_VARYING_SUBGROUP_SIZE_BIT_EXT flag set, the SubgroupSize decorated variable will contain the subgroup size for each subgroup that gets dispatched. This value must be between minSubgroupSize and maxSubgroupSize and must be uniform with subgroup scope. The value may vary across a single draw or dispatch call, and for fragment shaders may vary across a single primitive.

If the pipeline was created with a chained VkPipelineShaderStageRequiredSubgroupSizeCreateInfoEXT structure, the SubgroupSize decorated variable will match requiredSubgroupSize.

If the pipeline was not created with the VK_PIPELINE_SHADER_STAGE_CREATE_ALLOW_VARYING_SUBGROUP_SIZE_BIT_EXT flag set and no VkPipelineShaderStageRequiredSubgroupSizeCreateInfoEXT structure was chained, the variable decorated with SubgroupSize will match subgroupSize.

The maximum number of invocations that an implementation can support per subgroup is 128.

Valid Usage
  • VUID-SubgroupSize-SubgroupSize-04382
    The variable decorated with SubgroupSize must be declared using the Input Storage Class

  • VUID-SubgroupSize-SubgroupSize-04383
    The variable decorated with SubgroupSize must be declared as a scalar 32-bit integer value

TaskCountNV

Decorating a variable with the TaskCountNV decoration will make that variable contain the task count. The task count specifies the number of subsequent mesh shader workgroups that get generated upon completion of the task shader.

Valid Usage
  • VUID-TaskCountNV-TaskCountNV-04384
    The TaskCountNV decoration must be used only within the TaskNV Execution Model

  • VUID-TaskCountNV-TaskCountNV-04385
    The variable decorated with TaskCountNV must be declared using the Output Storage Class

  • VUID-TaskCountNV-TaskCountNV-04386
    The variable decorated with TaskCountNV must be declared as a scalar 32-bit integer value

TessCoord

Decorating a variable with the TessCoord built-in decoration will make that variable contain the three-dimensional (u,v,w) barycentric coordinate of the tessellated vertex within the patch. u, v, and w are in the range [0,1] and vary linearly across the primitive being subdivided. For the tessellation modes of Quads or IsoLines, the third component is always zero.

Valid Usage
  • VUID-TessCoord-TessCoord-04387
    The TessCoord decoration must be used only within the TessellationEvaluation Execution Model

  • VUID-TessCoord-TessCoord-04388
    The variable decorated with TessCoord must be declared using the Input Storage Class

  • VUID-TessCoord-TessCoord-04389
    The variable decorated with TessCoord must be declared as a three-component vector of 32-bit floating-point values

TessLevelOuter

Decorating a variable with the TessLevelOuter built-in decoration will make that variable contain the outer tessellation levels for the current patch.

In tessellation control shaders, the variable decorated with TessLevelOuter can be written to, which controls the tessellation factors for the resulting patch. These values are used by the tessellator to control primitive tessellation and can be read by tessellation evaluation shaders.

In tessellation evaluation shaders, the variable decorated with TessLevelOuter can read the values written by the tessellation control shader.

Valid Usage
  • VUID-TessLevelOuter-TessLevelOuter-04390
    The TessLevelOuter decoration must be used only within the TessellationControl or TessellationEvaluation Execution Model

  • VUID-TessLevelOuter-TessLevelOuter-04391
    The variable decorated with TessLevelOuter within the TessellationControl Execution Model must be declared using the Output Storage Class

  • VUID-TessLevelOuter-TessLevelOuter-04392
    The variable decorated with TessLevelOuter within the TessellationEvaluation Execution Model must be declared using the Input Storage Class

  • VUID-TessLevelOuter-TessLevelOuter-04393
    The variable decorated with TessLevelOuter must be declared as an array of size four, containing 32-bit floating-point values

TessLevelInner

Decorating a variable with the TessLevelInner built-in decoration will make that variable contain the inner tessellation levels for the current patch.

In tessellation control shaders, the variable decorated with TessLevelInner can be written to, which controls the tessellation factors for the resulting patch. These values are used by the tessellator to control primitive tessellation and can be read by tessellation evaluation shaders.

In tessellation evaluation shaders, the variable decorated with TessLevelInner can read the values written by the tessellation control shader.

Valid Usage
  • VUID-TessLevelInner-TessLevelInner-04394
    The TessLevelInner decoration must be used only within the TessellationControl or TessellationEvaluation Execution Model

  • VUID-TessLevelInner-TessLevelInner-04395
    The variable decorated with TessLevelInner within the TessellationControl Execution Model must be declared using the Output Storage Class

  • VUID-TessLevelInner-TessLevelInner-04396
    The variable decorated with TessLevelInner within the TessellationEvaluation Execution Model must be declared using the Input Storage Class

  • VUID-TessLevelInner-TessLevelInner-04397
    The variable decorated with TessLevelInner must be declared as an array of size two, containing 32-bit floating-point values

VertexIndex

Decorating a variable with the VertexIndex built-in decoration will make that variable contain the index of the vertex that is being processed by the current vertex shader invocation. For non-indexed draws, this variable begins at the firstVertex parameter to vkCmdDraw or the firstVertex member of a structure consumed by vkCmdDrawIndirect and increments by one for each vertex in the draw. For indexed draws, its value is the content of the index buffer for the vertex plus the vertexOffset parameter to vkCmdDrawIndexed or the vertexOffset member of the structure consumed by vkCmdDrawIndexedIndirect.

Note

VertexIndex starts at the same starting value for each instance.

Valid Usage
  • VUID-VertexIndex-VertexIndex-04398
    The VertexIndex decoration must be used only within the Vertex Execution Model

  • VUID-VertexIndex-VertexIndex-04399
    The variable decorated with VertexIndex must be declared using the Input Storage Class

  • VUID-VertexIndex-VertexIndex-04400
    The variable decorated with VertexIndex must be declared as a scalar 32-bit integer value

ViewIndex

The ViewIndex decoration can be applied to a shader input which will be filled with the index of the view that is being processed by the current shader invocation.

If multiview is enabled in the render pass, this value will be one of the bits set in the view mask of the subpass the pipeline is compiled against. If multiview is not enabled in the render pass, this value will be zero.

Valid Usage
  • VUID-ViewIndex-ViewIndex-04401
    The ViewIndex decoration must not be used within the GLCompute Execution Model

  • VUID-ViewIndex-ViewIndex-04402
    The variable decorated with ViewIndex must be declared using the Input Storage Class

  • VUID-ViewIndex-ViewIndex-04403
    The variable decorated with ViewIndex must be declared as a scalar 32-bit integer value

ViewportIndex

Decorating a variable with the ViewportIndex built-in decoration will make that variable contain the index of the viewport.

In a mesh, vertex, tessellation evaluation, or geometry shader, the variable decorated with ViewportIndex can be written to with the viewport index to which the primitive produced by that shader will be directed.

The selected viewport index is used to select the viewport transform, scissor rectangle, and exclusive scissor rectangle.

The last active vertex processing stage (in pipeline order) controls the ViewportIndex that is used. Outputs in previous shader stages are not used, even if the last stage fails to write the ViewportIndex.

If the last active vertex processing stage shader entry point’s interface does not include a variable decorated with ViewportIndex, then the first viewport is used. If a vertex processing stage shader entry point’s interface includes a variable decorated with ViewportIndex, it must write the same value to ViewportIndex for all output vertices of a given primitive.

In a fragment shader, the variable decorated with ViewportIndex contains the viewport index of the primitive that the fragment invocation belongs to.

Valid Usage
  • VUID-ViewportIndex-ViewportIndex-04404
    The ViewportIndex decoration must be used only within the MeshNV, Vertex, TessellationEvaluation, Geometry, or Fragment Execution Model

  • VUID-ViewportIndex-ViewportIndex-04405
    If the shaderOutputViewportIndex feature is not enabled then the ViewportIndex decoration must be used only within the Geometry or Fragment Execution Model

  • VUID-ViewportIndex-ViewportIndex-04406
    The variable decorated with ViewportIndex within the MeshNV, Vertex, TessellationEvaluation, or Geometry Execution Model must be declared using the Output Storage Class

  • VUID-ViewportIndex-ViewportIndex-04407
    The variable decorated with ViewportIndex within the Fragment Execution Model must be declared using the Input Storage Class

  • VUID-ViewportIndex-ViewportIndex-04408
    The variable decorated with ViewportIndex must be declared as a scalar 32-bit integer value

ViewportMaskNV

Decorating a variable with the ViewportMaskNV built-in decoration will make that variable contain the viewport mask.

In a mesh, vertex, tessellation evaluation, or geometry shader, the variable decorated with ViewportMaskNV can be written to with the mask of which viewports the primitive produced by that shader will directed.

The ViewportMaskNV variable must be an array that has ⌈(VkPhysicalDeviceLimits::maxViewports / 32)⌉ elements. When a shader writes to this variable, bit B of element M controls whether a primitive is emitted to viewport 32 × M + B. The viewports indicated by the mask are used to select the viewport transform, scissor rectangle, and exclusive scissor rectangle that a primitive will be transformed by.

The last active vertex processing stage (in pipeline order) controls the ViewportMaskNV that is used. Outputs in previous shader stages are not used, even if the last stage fails to write the ViewportMaskNV. When ViewportMaskNV is written by the final vertex processing stage, any variable decorated with ViewportIndex in the fragment shader will have the index of the viewport that was used in generating that fragment.

If a vertex processing stage shader entry point’s interface includes a variable decorated with ViewportMaskNV, it must write the same value to ViewportMaskNV for all output vertices of a given primitive.

Valid Usage
  • VUID-ViewportMaskNV-ViewportMaskNV-04409
    The ViewportMaskNV decoration must be used only within the Vertex, MeshNV, TessellationEvaluation, or Geometry Execution Model

  • VUID-ViewportMaskNV-ViewportMaskNV-04410
    The variable decorated with ViewportMaskNV must be declared using the Output Storage Class

  • VUID-ViewportMaskNV-ViewportMaskNV-04411
    The variable decorated with ViewportMaskNV must be declared as an array of 32-bit integer values

ViewportMaskPerViewNV

Decorating a variable with the ViewportMaskPerViewNV built-in decoration will make that variable contain the mask of viewports primitives are broadcast to, for each view.

The value written to an element of ViewportMaskPerViewNV in the last vertex processing stage is a bitmask indicating which viewports the primitive will be directed to. The primitive will be broadcast to the viewport corresponding to each non-zero bit of the bitmask, and that viewport index is used to select the viewport transform, scissor rectangle, and exclusive scissor rectangle, for each view. The same values must be written to all vertices in a given primitive, or else the set of viewports used for that primitive is undefined.

Elements of the array correspond to views in a multiview subpass, and those elements corresponding to views in the view mask of the subpass the shader is compiled against will be used as the viewport mask value for those views. ViewportMaskPerViewNV output in an earlier vertex processing stage is not available as an input in the subsequent vertex processing stage.

Although ViewportMaskNV is an array, ViewportMaskPerViewNV is not a two-dimensional array. Instead, ViewportMaskPerViewNV is limited to 32 viewports.

Valid Usage
  • VUID-ViewportMaskPerViewNV-ViewportMaskPerViewNV-04412
    The ViewportMaskPerViewNV decoration must be used only within the Vertex, MeshNV, TessellationControl, TessellationEvaluation, or Geometry Execution Model

  • VUID-ViewportMaskPerViewNV-ViewportMaskPerViewNV-04413
    The variable decorated with ViewportMaskPerViewNV must be declared using the Output Storage Class

  • VUID-ViewportMaskPerViewNV-ViewportMaskPerViewNV-04414
    The variable decorated with ViewportMaskPerViewNV must be declared as an array of 32-bit integer values

  • VUID-ViewportMaskPerViewNV-ViewportMaskPerViewNV-04415
    The array decorated with ViewportMaskPerViewNV must be a size less than or equal to 32

  • VUID-ViewportMaskPerViewNV-ViewportMaskPerViewNV-04416
    The array decorated with ViewportMaskPerViewNV must be a size greater than the maximum view in the subpass’s view mask

  • VUID-ViewportMaskPerViewNV-ViewportMaskPerViewNV-04417
    The array variable decorated with ViewportMaskPerViewNV must only be indexed by a constant or specialization constant.

WarpsPerSMNV

Decorating a variable with the WarpsPerSMNV built-in decoration will make that variable contain the maximum number of warps executing on a SM.

Valid Usage
  • VUID-WarpsPerSMNV-WarpsPerSMNV-04418
    The variable decorated with WarpsPerSMNV must be declared using the Input Storage Class

  • VUID-WarpsPerSMNV-WarpsPerSMNV-04419
    The variable decorated with WarpsPerSMNV must be declared as a scalar 32-bit integer value

WarpIDNV

Decorating a variable with the WarpIDNV built-in decoration will make that variable contain the ID of the warp on a SM on which the current shader invocation is running. This variable is in the range [0, WarpsPerSMNV-1].

Valid Usage
  • VUID-WarpIDNV-WarpIDNV-04420
    The variable decorated with WarpIDNV must be declared using the Input Storage Class

  • VUID-WarpIDNV-WarpIDNV-04421
    The variable decorated with WarpIDNV must be declared as a scalar 32-bit integer value

WorkgroupId

Decorating a variable with the WorkgroupId built-in decoration will make that variable contain the global workgroup that the current invocation is a member of. Each component ranges from a base value to a base + count value, based on the parameters passed into the dispatch commands.

Valid Usage
  • VUID-WorkgroupId-WorkgroupId-04422
    The WorkgroupId decoration must be used only within the GLCompute, MeshNV, or TaskNV Execution Model

  • VUID-WorkgroupId-WorkgroupId-04423
    The variable decorated with WorkgroupId must be declared using the Input Storage Class

  • VUID-WorkgroupId-WorkgroupId-04424
    The variable decorated with WorkgroupId must be declared as a three-component vector of 32-bit integer values

WorkgroupSize

Decorating an object with the WorkgroupSize built-in decoration will make that object contain the dimensions of a local workgroup. If an object is decorated with the WorkgroupSize decoration, this must take precedence over any execution mode set for LocalSize.

Valid Usage
  • VUID-WorkgroupSize-WorkgroupSize-04425
    The WorkgroupSize decoration must be used only within the GLCompute, MeshNV, or TaskNV Execution Model

  • VUID-WorkgroupSize-WorkgroupSize-04426
    The variable decorated with WorkgroupSize must be a specialization constant or a constant

  • VUID-WorkgroupSize-WorkgroupSize-04427
    The variable decorated with WorkgroupSize must be declared as a three-component vector of 32-bit integer values

WorldRayDirectionKHR

A variable decorated with the WorldRayDirectionKHR decoration will specify the direction of the ray being processed, in world space.

Valid Usage
  • VUID-WorldRayDirectionKHR-WorldRayDirectionKHR-04428
    The WorldRayDirectionKHR decoration must be used only within the IntersectionKHR, AnyHitKHR, ClosestHitKHR, or MissKHR Execution Model

  • VUID-WorldRayDirectionKHR-WorldRayDirectionKHR-04429
    The variable decorated with WorldRayDirectionKHR must be declared using the Input Storage Class

  • VUID-WorldRayDirectionKHR-WorldRayDirectionKHR-04430
    The variable decorated with WorldRayDirectionKHR must be declared as a three-component vector of 32-bit floating-point values

WorldRayOriginKHR

A variable decorated with the WorldRayOriginKHR decoration will specify the origin of the ray being processed, in world space.

Valid Usage
  • VUID-WorldRayOriginKHR-WorldRayOriginKHR-04431
    The WorldRayOriginKHR decoration must be used only within the IntersectionKHR, AnyHitKHR, ClosestHitKHR, or MissKHR Execution Model

  • VUID-WorldRayOriginKHR-WorldRayOriginKHR-04432
    The variable decorated with WorldRayOriginKHR must be declared using the Input Storage Class

  • VUID-WorldRayOriginKHR-WorldRayOriginKHR-04433
    The variable decorated with WorldRayOriginKHR must be declared as a three-component vector of 32-bit floating-point values

WorldToObjectKHR

A variable decorated with the WorldToObjectKHR decoration will contain the current world-to-object transformation matrix, which is determined by the instance of the current intersection.

Valid Usage
  • VUID-WorldToObjectKHR-WorldToObjectKHR-04434
    The WorldToObjectKHR decoration must be used only within the IntersectionKHR, AnyHitKHR, or ClosestHitKHR Execution Model

  • VUID-WorldToObjectKHR-WorldToObjectKHR-04435
    The variable decorated with WorldToObjectKHR must be declared using the Input Storage Class

  • VUID-WorldToObjectKHR-WorldToObjectKHR-04436
    The variable decorated with WorldToObjectKHR must be declared as a matrix with four columns of three-component vectors of 32-bit floating-point values