// Copyright (c) 2015-2016 The Khronos Group Inc. // Copyright notice at https://www.khronos.org/registry/speccopyright.html [[descriptorsets]] = Resource Descriptors Shaders access buffer and image resources by using special shader variables which are indirectly bound to buffer and image views via the API. These variables are organized into sets, where each set of bindings is represented by a _descriptor set_ object in the API and a descriptor set is bound all at once. A _descriptor_ is an opaque data structure representing a shader resource such as a buffer view, image view, sampler, or combined image sampler. The content of each set is determined by its _descriptor set layout_ and the sequence of set layouts that can: be used by resource variables in shaders within a pipeline is specified in a _pipeline layout_. Each shader can: use up to pname:maxBoundDescriptorSets (see <>) descriptor sets, and each descriptor set can: include bindings for descriptors of all descriptor types. Each shader resource variable is assigned a tuple of (set number, binding number, array element) that defines its location within a descriptor set layout. In GLSL, the set number and binding number are assigned via layout qualifiers, and the array element is implicitly assigned consecutively starting with index equal to zero for the first element of an array (and array element is zero for non-array variables): .GLSL example [source,{basebackend@docbook:c:glsl}] --------------------------------------------------- // Assign set number = M, binding number = N, array element = 0 layout (set=m, binding=n) uniform sampler2D variableName; // Assign set number = M, binding number = N for all array elements, and // array element = i for the i'th member of the array. layout (set=m, binding=n) uniform sampler2D variableNameArray[L]; --------------------------------------------------- .SPIR-V example --------------------------------------------------- // Assign set number = M, binding number = N, array element = 0 ... %1 = OpExtInstImport "GLSL.std.450" ... OpName %10 "variableName" OpDecorate %10 DescriptorSet m OpDecorate %10 Binding n %2 = OpTypeVoid %3 = OpTypeFunction %2 %6 = OpTypeFloat 32 %7 = OpTypeImage %6 2D 0 0 0 1 Unknown %8 = OpTypeSampledImage %7 %9 = OpTypePointer UniformConstant %8 %10 = OpVariable %9 UniformConstant ... // Assign set number = M, binding number = N for all array elements, and // array element = i for the i'th member of the array. ... %1 = OpExtInstImport "GLSL.std.450" ... OpName %13 "variableNameArray" OpDecorate %13 DescriptorSet m OpDecorate %13 Binding n %2 = OpTypeVoid %3 = OpTypeFunction %2 %6 = OpTypeFloat 32 %7 = OpTypeImage %6 2D 0 0 0 1 Unknown %8 = OpTypeSampledImage %7 %9 = OpTypeInt 32 0 %10 = OpConstant %9 L %11 = OpTypeArray %8 %10 %12 = OpTypePointer UniformConstant %11 %13 = OpVariable %12 UniformConstant ... --------------------------------------------------- [[descriptorsets-types]] == Descriptor Types The following sections outline the various descriptor types supported by {apiname}. Each section defines a descriptor type, and each descriptor type has a manifestation in the shading language and SPIR-V as well as in descriptor sets. There is mostly a one-to-one correspondence between descriptor types and classes of opaque types in the shading language, where the opaque types in the shading language must: refer to a descriptor in the pipeline layout of the corresponding descriptor type. But there is an exception to this rule as described in <>. [[descriptorsets-storageimage]] === Storage Image A _storage image_ (ename:VK_DESCRIPTOR_TYPE_STORAGE_IMAGE) is a descriptor type that is used for load, store, and atomic operations on image memory from within shaders bound to pipelines. Loads from storage images do not use samplers and are unfiltered and do not support coordinate wrapping or clamping. Loads are supported in all shader stages for image formats which report support for the <> feature bit via flink:vkGetPhysicalDeviceFormatProperties. Stores to storage images are supported in compute shaders for image formats which report support for the ename:VK_FORMAT_FEATURE_STORAGE_IMAGE_BIT feature. Storage images also support atomic operations in compute shaders for image formats which report support for the <> feature. Load and store operations on storage images can: only be done on images in ename:VK_IMAGE_LAYOUT_GENERAL layout. When the <> feature is enabled, stores and atomic operations are also supported for storage images in fragment shaders with the same set of image formats as supported in compute shaders. When the <> feature is enabled, stores and atomic operations are also supported in vertex, tessellation, and geometry shaders with the same set of image formats as supported in compute shaders. Storage image declarations must: specify the image format in the shader if the variable is used for atomic operations. If the <> feature is not enabled, storage image declarations must: specify the image format in the shader if the variable is used for load operations. If the <> feature is not enabled, storage image declarations must: specify the image format in the shader if the variable is used for store operations. Storage images are declared in GLSL shader source using uniform ``image'' variables of the appropriate dimensionality as well as a format layout qualifier (if necessary): .GLSL example [source,{basebackend@docbook:c:glsl}] --------------------------------------------------- layout (set=m, binding=n, r32f) uniform image2D myStorageImage; --------------------------------------------------- .SPIR-V example --------------------------------------------------- ... %1 = OpExtInstImport "GLSL.std.450" ... OpName %9 "myStorageImage" OpDecorate %9 DescriptorSet m OpDecorate %9 Binding n %2 = OpTypeVoid %3 = OpTypeFunction %2 %6 = OpTypeFloat 32 %7 = OpTypeImage %6 2D 0 0 0 2 R32f %8 = OpTypePointer UniformConstant %7 %9 = OpVariable %8 UniformConstant ... --------------------------------------------------- [[descriptorsets-sampler]] === Sampler A _sampler_ (ename:VK_DESCRIPTOR_TYPE_SAMPLER) represents a set of parameters which control address calculations, filtering behavior, and other properties, that can: be used to perform filtered loads from _sampled images_ (see <>). Samplers are declared in GLSL shader source using uniform ``sampler'' variables, where the sampler type has no associated texture dimensionality: .GLSL Example [source,{basebackend@docbook:c:glsl}] --------------------------------------------------- layout (set=m, binding=n) uniform sampler mySampler; --------------------------------------------------- .SPIR-V Example --------------------------------------------------- ... %1 = OpExtInstImport "GLSL.std.450" ... OpName %8 "mySampler" OpDecorate %8 DescriptorSet m OpDecorate %8 Binding n %2 = OpTypeVoid %3 = OpTypeFunction %2 %6 = OpTypeSampler %7 = OpTypePointer UniformConstant %6 %8 = OpVariable %7 UniformConstant ... --------------------------------------------------- [[descriptorsets-sampledimage]] === Sampled Image A _sampled image_ (ename:VK_DESCRIPTOR_TYPE_SAMPLED_IMAGE) can: be used (usually in conjunction with a sampler) to retrieve sampled image data. Shaders use a sampled image handle and a sampler handle to sample data, where the image handle generally defines the shape and format of the memory and the sampler generally defines how coordinate addressing is performed. The same sampler can: be used to sample from multiple images, and it is possible to sample from the same sampled image with multiple samplers, each containing a different set of sampling parameters. Sampled images are declared in GLSL shader source using uniform ``texture'' variables of the appropriate dimensionality: .GLSL example [source,{basebackend@docbook:c:glsl}] --------------------------------------------------- layout (set=m, binding=n) uniform texture2D mySampledImage; --------------------------------------------------- .SPIR-V example --------------------------------------------------- ... %1 = OpExtInstImport "GLSL.std.450" ... OpName %9 "mySampledImage" OpDecorate %9 DescriptorSet m OpDecorate %9 Binding n %2 = OpTypeVoid %3 = OpTypeFunction %2 %6 = OpTypeFloat 32 %7 = OpTypeImage %6 2D 0 0 0 1 Unknown %8 = OpTypePointer UniformConstant %7 %9 = OpVariable %8 UniformConstant ... --------------------------------------------------- [[descriptorsets-combinedimagesampler]] === Combined Image Sampler A _combined image sampler_ (ename:VK_DESCRIPTOR_TYPE_COMBINED_IMAGE_SAMPLER) represents a sampled image along with a set of sampling parameters. It is logically considered a sampled image and a sampler bound together. [NOTE] .Note ==== On some implementations, it may: be more efficient to sample from an image using a combination of sampler and sampled image that are stored together in the descriptor set in a combined descriptor. ==== Combined image samplers are declared in GLSL shader source using uniform ``sampler'' variables of the appropriate dimensionality: .GLSL example [source,{basebackend@docbook:c:glsl}] --------------------------------------------------- layout (set=m, binding=n) uniform sampler2D myCombinedImageSampler; --------------------------------------------------- .SPIR-V example --------------------------------------------------- ... %1 = OpExtInstImport "GLSL.std.450" ... OpName %10 "myCombinedImageSampler" OpDecorate %10 DescriptorSet m OpDecorate %10 Binding n %2 = OpTypeVoid %3 = OpTypeFunction %2 %6 = OpTypeFloat 32 %7 = OpTypeImage %6 2D 0 0 0 1 Unknown %8 = OpTypeSampledImage %7 %9 = OpTypePointer UniformConstant %8 %10 = OpVariable %9 UniformConstant ... --------------------------------------------------- ename:VK_DESCRIPTOR_TYPE_COMBINED_IMAGE_SAMPLER descriptor set entries can: also be accessed via separate sampler and sampled image shader variables. Such variables refer exclusively to the corresponding half of the descriptor, and can: be combined in the shader with samplers or sampled images that can: come from the same descriptor or from other combined or separate descriptor types. There are no additional restrictions on how a separate sampler or sampled image variable is used due to it originating from a combined descriptor. [[descriptorsets-uniformtexelbuffer]] === Uniform Texel Buffer A _uniform texel buffer_ (ename:VK_DESCRIPTOR_TYPE_UNIFORM_TEXEL_BUFFER) represents a tightly packed array of homogeneous formatted data that is stored in a buffer and is made accessible to shaders. Uniform texel buffers are read-only. Uniform texel buffers are declared in GLSL shader source using uniform ``samplerBuffer'' variables: .GLSL example [source,{basebackend@docbook:c:glsl}] --------------------------------------------------- layout (set=m, binding=n) uniform samplerBuffer myUniformTexelBuffer; --------------------------------------------------- .SPIR-V example --------------------------------------------------- ... %1 = OpExtInstImport "GLSL.std.450" ... OpName %10 "myUniformTexelBuffer" OpDecorate %10 DescriptorSet m OpDecorate %10 Binding n %2 = OpTypeVoid %3 = OpTypeFunction %2 %6 = OpTypeFloat 32 %7 = OpTypeImage %6 Buffer 0 0 0 1 Unknown %8 = OpTypeSampledImage %7 %9 = OpTypePointer UniformConstant %8 %10 = OpVariable %9 UniformConstant ... --------------------------------------------------- [[descriptorsets-storagetexelbuffer]] === Storage Texel Buffer A _storage texel buffer_ (ename:VK_DESCRIPTOR_TYPE_STORAGE_TEXEL_BUFFER) represents a tightly packed array of homogeneous formatted data that is stored in a buffer and is made accessible to shaders. Storage texel buffers differ from uniform texel buffers in that they support stores and atomic operations in shaders, may: support a different maximum length, and may: have different performance characteristics. Storage texel buffers are declared in GLSL shader source using uniform ``imageBuffer'' variables: .GLSL example [source,{basebackend@docbook:c:glsl}] --------------------------------------------------- layout (set=m, binding=n, r32f) uniform imageBuffer myStorageTexelBuffer; --------------------------------------------------- .SPIR-V example --------------------------------------------------- ... %1 = OpExtInstImport "GLSL.std.450" ... OpName %9 "myStorageTexelBuffer" OpDecorate %9 DescriptorSet m OpDecorate %9 Binding n %2 = OpTypeVoid %3 = OpTypeFunction %2 %6 = OpTypeFloat 32 %7 = OpTypeImage %6 Buffer 0 0 0 2 R32f %8 = OpTypePointer UniformConstant %7 %9 = OpVariable %8 UniformConstant ... --------------------------------------------------- [[descriptorsets-uniformbuffer]] === Uniform Buffer A _uniform buffer_ (ename:VK_DESCRIPTOR_TYPE_UNIFORM_BUFFER) is a region of structured storage that is made accessible for read-only access to shaders. It is typically used to store medium sized arrays of constants such as shader parameters, matrices and other related data. Uniform buffers are declared in GLSL shader source using the uniform storage qualifier and block syntax: .GLSL example [source,{basebackend@docbook:c:glsl}] --------------------------------------------------- layout (set=m, binding=n) uniform myUniformBuffer { vec4 myElement[32]; }; --------------------------------------------------- .SPIR-V example --------------------------------------------------- ... %1 = OpExtInstImport "GLSL.std.450" ... OpName %11 "myUniformBuffer" OpMemberName %11 0 "myElement" OpName %13 "" OpDecorate %10 ArrayStride 16 OpMemberDecorate %11 0 Offset 0 OpDecorate %11 Block OpDecorate %13 DescriptorSet m OpDecorate %13 Binding n %2 = OpTypeVoid %3 = OpTypeFunction %2 %6 = OpTypeFloat 32 %7 = OpTypeVector %6 4 %8 = OpTypeInt 32 0 %9 = OpConstant %8 32 %10 = OpTypeArray %7 %9 %11 = OpTypeStruct %10 %12 = OpTypePointer Uniform %11 %13 = OpVariable %12 Uniform ... --------------------------------------------------- [[descriptorsets-storagebuffer]] === Storage Buffer A _storage buffer_ (ename:VK_DESCRIPTOR_TYPE_STORAGE_BUFFER) is a region of structured storage that supports both read and write access for shaders. In addition to general read and write operations, some members of storage buffers can: be used as the target of atomic operations. In general, atomic operations are only supported on members that have unsigned integer formats. Storage buffers are declared in GLSL shader source using buffer storage qualifier and block syntax: .GLSL example [source,{basebackend@docbook:c:glsl}] --------------------------------------------------- layout (set=m, binding=n) buffer myStorageBuffer { vec4 myElement[]; }; --------------------------------------------------- .SPIR-V example --------------------------------------------------- ... %1 = OpExtInstImport "GLSL.std.450" ... OpName %9 "myStorageBuffer" OpMemberName %9 0 "myElement" OpName %11 "" OpDecorate %8 ArrayStride 16 OpMemberDecorate %9 0 Offset 0 OpDecorate %9 BufferBlock OpDecorate %11 DescriptorSet m OpDecorate %11 Binding n %2 = OpTypeVoid %3 = OpTypeFunction %2 %6 = OpTypeFloat 32 %7 = OpTypeVector %6 4 %8 = OpTypeRuntimeArray %7 %9 = OpTypeStruct %8 %10 = OpTypePointer Uniform %9 %11 = OpVariable %10 Uniform ... --------------------------------------------------- [[descriptorsets-uniformbufferdynamic]] === Dynamic Uniform Buffer A _dynamic uniform buffer_ (ename:VK_DESCRIPTOR_TYPE_UNIFORM_BUFFER_DYNAMIC) differs from a uniform buffer only in how its address and length are specified. Uniform buffers bind a buffer address and length that is specified in the descriptor set update by a buffer handle, offset and range (see <>). With dynamic uniform buffers the buffer handle, offset and range specified in the descriptor set define the base address and length. The dynamic offset which is relative to this base address is taken from the pname:pDynamicOffsets parameter to flink:vkCmdBindDescriptorSets (see <>). The address used for a dynamic uniform buffer is the sum of the buffer base address and the relative offset. The length is unmodified and remains the range as specified in the descriptor update. The shader syntax is identical for uniform buffers and dynamic uniform buffers. [[descriptorsets-storagebufferdynamic]] === Dynamic Storage Buffer A _dynamic storage buffer_ (ename:VK_DESCRIPTOR_TYPE_STORAGE_BUFFER_DYNAMIC) differs from a storage buffer only in how its address and length are specified. The difference is identical to the difference between uniform buffers and dynamic uniform buffers (see <>). The shader syntax is identical for storage buffers and dynamic storage buffers. [[descriptorsets-inputattachment]] === Input Attachment An _input attachment_ (ename:VK_DESCRIPTOR_TYPE_INPUT_ATTACHMENT) is an image view that can: be used for pixel local load operations from within fragment shaders bound to pipelines. Loads from input attachments are unfiltered. All image formats that are supported for color attachments (ename:VK_FORMAT_FEATURE_COLOR_ATTACHMENT_BIT) or depth/stencil attachments (ename:VK_FORMAT_FEATURE_DEPTH_STENCIL_ATTACHMENT_BIT) for a given image tiling mode are also supported for input attachments. In the shader, input attachments must: be decorated with their input attachment index in addition to descriptor set and binding numbers. .GLSL example [source,{basebackend@docbook:c:glsl}] --------------------------------------------------- layout (input_attachment_index=i, set=m, binding=n) uniform subpassInput myInputAttachment; --------------------------------------------------- .SPIR-V example --------------------------------------------------- ... %1 = OpExtInstImport "GLSL.std.450" ... OpName %9 "myInputAttachment" OpDecorate %9 DescriptorSet m OpDecorate %9 Binding n OpDecorate %9 InputAttachmentIndex i %2 = OpTypeVoid %3 = OpTypeFunction %2 %6 = OpTypeFloat 32 %7 = OpTypeImage %6 SubpassData 0 0 0 2 Unknown %8 = OpTypePointer UniformConstant %7 %9 = OpVariable %8 UniformConstant ... --------------------------------------------------- [[descriptorsets-sets]] == Descriptor Sets Descriptors are grouped together into descriptor set objects. A descriptor set object is an opaque object that contains storage for a set of descriptors, where the types and number of descriptors is defined by a descriptor set layout. The layout object may: be used to define the association of each descriptor binding with memory or other hardware resources. The layout is used both for determining the resources that need to be associated with the descriptor set, and determining the interface between shader stages and shader resources. [[descriptorsets-setlayout]] === Descriptor Set Layout A descriptor set layout object is defined by an array of zero or more descriptor bindings. Each individual descriptor binding is specified by a descriptor type, a count (array size) of the number of descriptors in the binding, a set of shader stages that can: access the binding, and (if using immutable samplers) an array of sampler descriptors. Descriptor set layouts are represented by sname:VkDescriptorSetLayout objects which are created by calling: include::../protos/vkCreateDescriptorSetLayout.txt[] * pname:device is the logical device that creates the descriptor set layout. * pname:pCreateInfo is a pointer to an instance of the slink:VkDescriptorSetLayoutCreateInfo structure specifying the state of the descriptor set layout object. * pname:pAllocator controls host memory allocation as described in the <> chapter. * pname:pSetLayout points to a sname:VkDescriptorSetLayout handle in which the resulting descriptor set layout object is returned. include::../validity/protos/vkCreateDescriptorSetLayout.txt[] Information about the descriptor set layout is passed in an instance of the sname:VkDescriptorSetLayoutCreateInfo structure: include::../structs/VkDescriptorSetLayoutCreateInfo.txt[] * pname:sType is the type of this structure. * pname:pNext is `NULL` or a pointer to an extension-specific structure. * pname:flags is reserved for future use. * pname:bindingCount is the number of elements in pname:pBindings. * pname:pBindings is a pointer to an array of slink:VkDescriptorSetLayoutBinding structures. include::../validity/structs/VkDescriptorSetLayoutCreateInfo.txt[] The sname:VkDescriptorSetLayoutBinding structure is defined as: include::../structs/VkDescriptorSetLayoutBinding.txt[] * pname:binding is the binding number of this entry and corresponds to a resource of the same binding number in the shader stages. * pname:descriptorType is an elink:VkDescriptorType specifying which type of resource descriptors are used for this binding. * pname:descriptorCount is the number of descriptors contained in the binding, accessed in a shader as an array. If pname:descriptorCount is zero this binding entry is reserved and the resource mustnot: be accessed from any stage via this binding within any pipeline using the set layout. * pname:stageFlags member is a bitfield of elink:VkShaderStageFlagBits specifying which pipeline shader stages can: access a resource for this binding. ename:VK_SHADER_STAGE_ALL is a shorthand specifying that all defined shader stages, including any additional stages defined by extensions, can: access the resource. + If a shader stage is not included in pname:stageFlags, then a resource mustnot: be accessed from that stage via this binding within any pipeline using the set layout. There are no limitations on what combinations of stages can: be used by a descriptor binding, and in particular a binding can: be used by both graphics stages and the compute stage. * pname:pImmutableSamplers affects initialization of samplers. If pname:descriptorType specifies a ename:VK_DESCRIPTOR_TYPE_SAMPLER or ename:VK_DESCRIPTOR_TYPE_COMBINED_IMAGE_SAMPLER type descriptor, then pname:pImmutableSamplers can: be used to initialize a set of _immutable samplers_. Immutable samplers are permanently bound into the set layout; later binding a sampler into an immutable sampler slot in a descriptor set is not allowed. If pname:pImmutableSamplers is not `NULL`, then it is considered to be a pointer to an array of sampler handles that will be consumed by the set layout and used for the corresponding binding. If pname:pImmutableSamplers is `NULL`, then the sampler slots are dynamic and sampler handles must: be bound into descriptor sets using this layout. If pname:descriptorType is not one of these descriptor types, then pname:pImmutableSamplers is ignored. The above layout definition allows the descriptor bindings to be specified sparsely such that not all binding numbers between 0 and the maximum binding number need to be specified in the pname:pBindings array. However, all binding numbers between 0 and the maximum binding number may: consume memory in the descriptor set layout even if not all descriptor bindings are used, though it shouldnot: consume additional memory from the descriptor pool. [NOTE] .Note ==== The maximum binding number specified should: be as compact as possible to avoid wasted memory. ==== include::../validity/structs/VkDescriptorSetLayoutBinding.txt[] The following examples show a shader snippet using two descriptor sets, and application code that creates corresponding descriptor set layouts. .GLSL example [source,{basebackend@docbook:c:glsl}] --------------------------------------------------- // // binding to a single sampled image descriptor in set 0 // layout (set=0, binding=0) uniform texture2D mySampledImage; // // binding to an array of sampled image descriptors in set 0 // layout (set=0, binding=1) uniform texture2D myArrayOfSampledImages[12]; // // binding to a single uniform buffer descriptor in set 1 // layout (set=1, binding=0) uniform myUniformBuffer { vec4 myElement[32]; }; --------------------------------------------------- .SPIR-V example --------------------------------------------------- ... %1 = OpExtInstImport "GLSL.std.450" ... OpName %9 "mySampledImage" OpName %14 "myArrayOfSampledImages" OpName %18 "myUniformBuffer" OpMemberName %18 0 "myElement" OpName %20 "" OpDecorate %9 DescriptorSet 0 OpDecorate %9 Binding 0 OpDecorate %14 DescriptorSet 0 OpDecorate %14 Binding 1 OpDecorate %17 ArrayStride 16 OpMemberDecorate %18 0 Offset 0 OpDecorate %18 Block OpDecorate %20 DescriptorSet 1 OpDecorate %20 Binding 0 %2 = OpTypeVoid %3 = OpTypeFunction %2 %6 = OpTypeFloat 32 %7 = OpTypeImage %6 2D 0 0 0 1 Unknown %8 = OpTypePointer UniformConstant %7 %9 = OpVariable %8 UniformConstant %10 = OpTypeInt 32 0 %11 = OpConstant %10 12 %12 = OpTypeArray %7 %11 %13 = OpTypePointer UniformConstant %12 %14 = OpVariable %13 UniformConstant %15 = OpTypeVector %6 4 %16 = OpConstant %10 32 %17 = OpTypeArray %15 %16 %18 = OpTypeStruct %17 %19 = OpTypePointer Uniform %18 %20 = OpVariable %19 Uniform ... --------------------------------------------------- .API example [source,{basebackend@docbook:c++:cpp}] ------------------------------------------------------------------------------- VkResult myResult; const VkDescriptorSetLayoutBinding myDescriptorSetLayoutBinding[] = { // binding to a single image descriptor { 0, // binding VK_DESCRIPTOR_TYPE_SAMPLED_IMAGE, // descriptorType 1, // descriptorCount VK_SHADER_STAGE_FRAGMENT_BIT, // stageFlags NULL // pImmutableSamplers }, // binding to an array of image descriptors { 1, // binding VK_DESCRIPTOR_TYPE_SAMPLED_IMAGE, // descriptorType 12, // descriptorCount VK_SHADER_STAGE_FRAGMENT_BIT, // stageFlags NULL // pImmutableSamplers }, // binding to a single uniform buffer descriptor { 0, // binding VK_DESCRIPTOR_TYPE_UNIFORM_BUFFER, // descriptorType 1, // descriptorCount VK_SHADER_STAGE_FRAGMENT_BIT, // stageFlags NULL // pImmutableSamplers } }; const VkDescriptorSetLayoutCreateInfo myDescriptorSetLayoutCreateInfo[] = { // Create info for first descriptor set with two descriptor bindings { VK_STRUCTURE_TYPE_DESCRIPTOR_SET_LAYOUT_CREATE_INFO, // sType NULL, // pNext 0, // flags 2, // bindingCount &myDescriptorSetLayoutBinding[0] // pBindings }, // Create info for second descriptor set with one descriptor binding { VK_STRUCTURE_TYPE_DESCRIPTOR_SET_LAYOUT_CREATE_INFO, // sType NULL, // pNext 0, // flags 1, // bindingCount &myDescriptorSetLayoutBinding[2] // pBindings } }; VkDescriptorSetLayout myDescriptorSetLayout[2]; // // Create first descriptor set layout // myResult = vkCreateDescriptorSetLayout( myDevice, &myDescriptorSetLayoutCreateInfo[0], NULL, &myDescriptorSetLayout[0]); // // Create second descriptor set layout // myResult = vkCreateDescriptorSetLayout( myDevice, &myDescriptorSetLayoutCreateInfo[1], NULL, &myDescriptorSetLayout[1]); ------------------------------------------------------------------------------- To destroy a descriptor set layout, call: include::../protos/vkDestroyDescriptorSetLayout.txt[] * pname:device is the logical device that destroys the descriptor set layout. * pname:descriptorSetLayout is the descriptor set layout to destroy. * pname:pAllocator controls host memory allocation as described in the <> chapter. include::../validity/protos/vkDestroyDescriptorSetLayout.txt[] [[descriptorsets-pipelinelayout]] === Pipeline Layouts Access to descriptor sets from a pipeline is accomplished through a _pipeline layout_. Zero or more descriptor set layouts and zero or more push constant ranges are combined to form a pipeline layout object which describes the complete set of resources that can: be accessed by a pipeline. The pipeline layout represents a sequence of descriptor sets with each having a specific layout. This sequence of layouts is used to determine the interface between shader stages and shader resources. Each pipeline is created using a pipeline layout. A pipeline layout is created by calling: include::../protos/vkCreatePipelineLayout.txt[] * pname:device is the logical device that creates the pipeline layout. * pname:pCreateInfo is a pointer to an instance of the slink:VkPipelineLayoutCreateInfo structure specifying the state of the pipeline layout object. * pname:pAllocator controls host memory allocation as described in the <> chapter. * pname:pPipelineLayout points to a sname:VkPipelineLayout handle in which the resulting pipeline layout object is returned. include::../validity/protos/vkCreatePipelineLayout.txt[] The slink:VkPipelineLayoutCreateInfo structure is defined as: include::../structs/VkPipelineLayoutCreateInfo.txt[] * pname:sType is the type of this structure. * pname:pNext is `NULL` or a pointer to an extension-specific structure. * pname:flags is reserved for future use. * pname:setLayoutCount is the number of descriptor sets included in the pipeline layout. * pname:pSetLayouts is a pointer to an array of sname:VkDescriptorSetLayout objects. * pname:pushConstantRangeCount is the number of push constant ranges included in the pipeline layout. * pname:pPushConstantRanges is a pointer to an array of sname:VkPushConstantRange structures defining a set of push constant ranges for use in a single pipeline layout. In addition to descriptor set layouts, a pipeline layout also describes how many push constants can: be accessed by each stage of the pipeline. + [NOTE] .Note ==== Push constants represent a high speed path to modify constant data in pipelines that is expected to outperform memory-backed resource updates. ==== include::../validity/structs/VkPipelineLayoutCreateInfo.txt[] The sname:VkPushConstantRange structure is defined as: include::../structs/VkPushConstantRange.txt[] * pname:stageFlags is a set of stage flags describing the shader stages that will access a range of push constants. If a particular stage is not included in the range, then accessing members of that range of push constants from the corresponding shader stage will result in undefined data being read. * pname:offset and pname:size are the start offset and size, respectively, consumed by the range. Both pname:offset and pname:size are in units of bytes and must: be a multiple of 4. The layout of the push constant variables is specified in the shader. include::../validity/structs/VkPushConstantRange.txt[] Once created, pipeline layouts are used as part of pipeline creation (see <>), as part of binding descriptor sets (see <>), and as part of setting push constants (see <>). Pipeline creation accepts a pipeline layout as input, and the layout may: be used to map (set, binding, arrayElement) tuples to hardware resources or memory locations within a descriptor set. The assignment of hardware resources depends only on the bindings defined in the descriptor sets that comprise the pipeline layout, and not on any shader source. [[descriptorsets-pipelinelayout-consistency]] All resource variables <> in all shaders in a pipeline must: be declared with a (set,binding,arrayElement) that exists in the corresponding descriptor set layout and is of an appropriate descriptor type and includes the set of shader stages it is used by in pname:stageFlags. The pipeline layout can: include entries that are not used by a particular pipeline, or that are dead-code eliminated from any of the shaders. The pipeline layout allows the application to provide a consistent set of bindings across multiple pipeline compiles, which enables those pipelines to be compiled in a way that the implementation may: cheaply switch pipelines without reprogramming the bindings. Similarly, the push constant block declared in each shader (if present) must: only place variables at offsets that are each included in a push constant range with pname:stageFlags including the bit corresponding to the shader stage that uses it. The pipeline layout can: include ranges or portions of ranges that are not used by a particular pipeline, or for which the variables have been dead-code eliminated from any of the shaders. There is a limit on the total number of resources of each type that can: be included in bindings in all descriptor set layouts in a pipeline layout as shown in <>. The ``Total Resources Available'' column gives the limit on the number of each type of resource that can: be included in bindings in all descriptor sets in the pipeline layout. Some resource types count against multiple limits. Additionally, there are limits on the total number of each type of resource that can: be used in any pipeline stage as described in <>. [[descriptorsets-pipelinelayout-limits]] .Pipeline Layout Resource Limits [width="80%",cols="<37,<22",options="header"] |============================= | Total Resources Available | Resource Types .2+<.^| maxDescriptorSetSamplers | sampler | combined image sampler .3+<.^| maxDescriptorSetSampledImages | sampled image | combined image sampler | uniform texel buffer .2+<.^| maxDescriptorSetStorageImages | storage image | storage texel buffer .2+<.^| maxDescriptorSetUniformBuffers | uniform buffer | uniform buffer dynamic | maxDescriptorSetUniformBuffersDynamic | uniform buffer dynamic .2+<.^| maxDescriptorSetStorageBuffers | storage buffer | storage buffer dynamic | maxDescriptorSetStorageBuffersDynamic | storage buffer dynamic | maxDescriptorSetInputAttachments | input attachment |============================= To destroy a pipeline layout, call: include::../protos/vkDestroyPipelineLayout.txt[] * pname:device is the logical device that destroys the pipeline layout. * pname:pipelineLayout is the pipeline layout to destroy. * pname:pAllocator controls host memory allocation as described in the <> chapter. include::../validity/protos/vkDestroyPipelineLayout.txt[] [[descriptorsets-compatibility]] ==== Pipeline Layout Compatibility Two pipeline layouts are defined to be ``compatible for <>'' if they were created with identical push constant ranges. Two pipeline layouts are defined to be ``compatible for set N'' if they were created with matching (the same, or identically defined) descriptor set layouts for sets zero through N, and if they were created with identical push constant ranges. When binding a descriptor set (see <>) to set number N, if the previously bound descriptor sets for sets zero through N-1 were all bound using compatible pipeline layouts, then performing this binding does not disturb any of the lower numbered sets. If, additionally, the previous bound descriptor set for set N was bound using a pipeline layout compatible for set N, then the bindings in sets numbered greater than N are also not disturbed. Similarly, when binding a pipeline, the pipeline can: correctly access any previously bound descriptor sets which were bound with compatible pipeline layouts, as long as all lower numbered sets were also bound with compatible layouts. Layout compatibility means that descriptor sets can: be bound to a command buffer for use by any pipeline created with a compatible pipeline layout, and without having bound a particular pipeline first. It also means that descriptor sets can: remain valid across a pipeline change, and the same resources will be accessible to the newly bound pipeline. ifdef::implementation-guide[] .Implementor's Note **** A consequence of layout compatibility is that when the implementation compiles a pipeline layout and assigns hardware units to resources, the mechanism to assign hardware units for set N should: only be a function of sets [0..N]. **** endif::implementation-guide[] [NOTE] .Note ==== Place the least frequently changing descriptor sets near the start of the pipeline layout, and place the descriptor sets representing the most frequently changing resources near the end. When pipelines are switched, only the descriptor set bindings that have been invalidated will need to be updated and the remainder of the descriptor set bindings will remain in place. ==== The maximum number of descriptor sets that can: be bound to a pipeline layout is queried from physical device properties (see pname:maxBoundDescriptorSets in <>). .API example [source,{basebackend@docbook:c++:cpp}] --------------------------------------------------- const VkDescriptorSetLayout layouts[] = { layout1, layout2 }; const VkPushConstantRange ranges[] = { { VK_PIPELINE_STAGE_VERTEX_SHADER_BIT, // stageFlags 0, // offset 4 // size }, { VK_PIPELINE_STAGE_FRAGMENT_SHADER_BIT, // stageFlags 4, // offset 4 // size }, }; const VkPipelineLayoutCreateInfo createInfo = { VK_STRUCTURE_TYPE_PIPELINE_LAYOUT_CREATE_INFO, // sType NULL, // pNext 0, // flags 2, // setLayoutCount layouts, // pSetLayouts 2, // pushConstantRangeCount ranges // pPushConstantRanges }; VkPipelineLayout myPipelineLayout; myResult = vkCreatePipelineLayout( myDevice, &createInfo, NULL, &myPipelineLayout); --------------------------------------------------- [[descriptorsets-allocation]] === Allocation of Descriptor Sets Descriptor sets are allocated from _descriptor pool_ objects. A descriptor pool maintains a pool of descriptors, from which sets are allocated. Descriptor pools are externally synchronized, meaning that the application mustnot: allocate and/or free descriptor sets from the same pool in multiple threads simultaneously. To create a descriptor pool object, call: include::../protos/vkCreateDescriptorPool.txt[] * pname:device is the logical device that creates the descriptor pool. * pname:pCreateInfo is a pointer to an instance of the slink:VkDescriptorPoolCreateInfo structure specifying the state of the descriptor pool object. * pname:pAllocator controls host memory allocation as described in the <> chapter. * pname:pDescriptorPool points to a sname:VkDescriptorPool handle in which the resulting descriptor pool object is returned. pname:pAllocator controls host memory allocation as described in the <> chapter. The created descriptor pool is returned in pname:pDescriptorPool. include::../validity/protos/vkCreateDescriptorPool.txt[] Additional information about the pool is passed in an instance of the sname:VkDescriptorPoolCreateInfo structure: include::../structs/VkDescriptorPoolCreateInfo.txt[] * pname:sType is the type of this structure. * pname:pNext is `NULL` or a pointer to an extension-specific structure. * pname:flags specifies certain supported operations on the pool, with possible values defined below. * pname:maxSets is the maximum number of descriptor sets that can: be allocated from the pool. * pname:poolSizeCount is the number of elements in pname:pPoolSizes. * pname:pPoolSizes is a pointer to an array of sname:VkDescriptorPoolSize structures, each containing a descriptor type and number of descriptors of that type to be allocated in the pool. include::../validity/structs/VkDescriptorPoolCreateInfo.txt[] If multiple sname:VkDescriptorPoolSize structures appear in the pname:pPoolSizes array then the pool will be created with enough storage for the total number of descriptors of each type. Fragmentation of a descriptor pool is possible and may: lead to descriptor set allocation failures. A failure due to fragmentation is defined as failing a descriptor set allocation despite the sum of all outstanding descriptor set allocations from the pool plus the requested allocation requiring no more than the total number of descriptors requested at pool creation. Implementations provide certain guarantees of when fragmentation mustnot: cause allocation failure, as described below. If a descriptor pool has not had any descriptor sets freed since it was created or most recently reset then fragmentation mustnot: cause an allocation failure (note that this is always the case for a pool created without the ename:VK_DESCRIPTOR_POOL_CREATE_FREE_DESCRIPTOR_SET_BIT bit set). Additionally, if all sets allocated from the pool since it was created or most recently reset use the same number of descriptors (of each type) and the requested allocation also uses that same number of descriptors (of each type), then fragmentation mustnot: cause an allocation failure. If an allocation failure occurs due to fragmentation, an application can: create an additional descriptor pool to perform further descriptor set allocations. The pname:flags member of sname:VkDescriptorPoolCreateInfo can: include the following values: include::../enums/VkDescriptorPoolCreateFlagBits.txt[] If pname:flags includes ename:VK_DESCRIPTOR_POOL_CREATE_FREE_DESCRIPTOR_SET_BIT, then descriptor sets can: return their individual allocations to the pool, i.e. all of fname:vkAllocateDescriptorSets, fname:vkFreeDescriptorSets, and fname:vkResetDescriptorPool are allowed. Otherwise, descriptor sets allocated from the pool mustnot: be individually freed back to the pool, i.e. only fname:vkAllocateDescriptorSets and fname:vkResetDescriptorPool are allowed. The sname:VkDescriptorPoolSize structure is defined as: include::../structs/VkDescriptorPoolSize.txt[] * pname:type is the type of descriptor. * pname:descriptorCount is the number of descriptors of that type to allocate. include::../validity/structs/VkDescriptorPoolSize.txt[] To destroy a descriptor pool, call: include::../protos/vkDestroyDescriptorPool.txt[] * pname:device is the logical device that destroys the descriptor pool. * pname:descriptorPool is the descriptor pool to destroy. * pname:pAllocator controls host memory allocation as described in the <> chapter. include::../validity/protos/vkDestroyDescriptorPool.txt[] When a pool is destroyed, all descriptor sets allocated from the pool are implicitly freed and become invalid. Descriptor sets allocated from a given pool do not need to be freed before destroying that descriptor pool. Descriptor sets are allocated from a descriptor pool by calling: include::../protos/vkAllocateDescriptorSets.txt[] * pname:device is the logical device that owns the descriptor pool. * pname:pAllocateInfo is a pointer to an instance of the slink:VkDescriptorSetAllocateInfo structure describing parameters of the allocation. * pname:pDescriptorSets is a pointer to an array of sname:VkDescriptorSet handles in which the resulting descriptor set objects are returned. The array must: be at least the length specified by the pname:descriptorSetCount member of pname:pAllocateInfo. include::../validity/protos/vkAllocateDescriptorSets.txt[] The sname:VkDescriptorSetAllocateInfo structure is defined as: include::../structs/VkDescriptorSetAllocateInfo.txt[] * pname:sType is the type of this structure. * pname:pNext is `NULL` or a pointer to an extension-specific structure. * pname:descriptorPool is the pool which the sets will be allocated from. * pname:descriptorSetCount determines the number of descriptor sets to be allocated from the pool. * pname:pSetLayouts is an array of descriptor set layouts, with each member specifying how the corresponding descriptor set is allocated. The allocated descriptor sets are returned in pname:pDescriptorSets. include::../validity/structs/VkDescriptorSetAllocateInfo.txt[] When a descriptor set is allocated, the initial state is largely uninitialized and all descriptors are undefined. However, the descriptor set can: be bound in a command buffer without causing errors or exceptions. All entries that are statically used by a pipeline in a drawing or dispatching command must: have been populated before the descriptor set is bound for use by that command. Entries that are not statically used by a pipeline can: have uninitialized descriptors or descriptors of resources that have been destroyed, and executing a draw or dispatch with such a descriptor set bound does not cause undefined behavior. This means applications need not populate unused entries with dummy descriptors. Allocated descriptor sets are freed by calling: include::../protos/vkFreeDescriptorSets.txt[] * pname:device is the logical device that owns the descriptor pool. * pname:descriptorPool is the descriptor pool from which the descriptor sets were allocated. * pname:descriptorSetCount is the number of elements in the pname:pDescriptorSets array. * pname:pDescriptorSets is an array of handles to sname:VkDescriptorSet objects. All elements of pname:pDescriptorSets must: have been allocated from pname:descriptorPool. In order to free individual descriptor sets, pname:descriptorPool must: have been created with the ename:VK_DESCRIPTOR_POOL_CREATE_FREE_DESCRIPTOR_SET_BIT flag. ifdef::editing-notes[] [NOTE] .editing-note ==== (Jon) Several comments above seem like they belong in validity XML. ==== endif::editing-notes[] include::../validity/protos/vkFreeDescriptorSets.txt[] After a successful call to fname:vkFreeDescriptorSets, all descriptor sets in pname:pDescriptorSets are invalid. Rather than freeing individual descriptor sets, all descriptor sets allocated from a given pool can: be returned to the pool by calling: include::../protos/vkResetDescriptorPool.txt[] * pname:device is the logical device that owns the descriptor pool. * pname:descriptorPool is the descriptor pool to be reset. * pname:flags is currently unused and must: be zero. include::../validity/protos/vkResetDescriptorPool.txt[] Resetting a descriptor pool recycles all of the resources from all of the descriptor sets allocated from the descriptor pool back to the descriptor pool, and the descriptor sets are implicitly freed. [[descriptorsets-updates]] === Descriptor Set Updates Once allocated, descriptor sets can: be updated with a combination of write and copy operations. To update descriptor sets, call: include::../protos/vkUpdateDescriptorSets.txt[] * pname:device is the logical device that updates the descriptor sets. * pname:descriptorWriteCount is the number of elements in the pname:pDescriptorWrites array. * pname:pDescriptorWrites is a pointer to an array of slink:VkWriteDescriptorSet structures describing the descriptor sets to write to. * pname:descriptorCopyCount is the number of elements in the pname:pDescriptorCopies array. * pname:pDescriptorCopies is a pointer to an array of slink:VkCopyDescriptorSet structures describing the descriptor sets to copy between. The operations described by pname:pDescriptorWrites are performed first, followed by the operations described by pname:pDescriptorCopies. Within each array, the operations are performed in the order they appear in the array. include::../validity/protos/vkUpdateDescriptorSets.txt[] Each element in the pname:pDescriptorWrites array describes an operation updating the descriptor set using descriptors for resources specified in the structure. The sname:VkWriteDescriptorSet structure is defined as: include::../structs/VkWriteDescriptorSet.txt[] * pname:sType is the type of this structure. * pname:pNext is `NULL` or a pointer to an extension-specific structure. * pname:dstSet is the destination descriptor set to update. * pname:dstBinding is the descriptor binding within that set. * pname:dstArrayElement is the starting element in that array. * pname:descriptorCount is the number of descriptors to update (the number of elements in pname:pImageInfo, pname:pBufferInfo, or pname:pTexelBufferView). * pname:descriptorType is the type of each descriptor in pname:pImageInfo, pname:pBufferInfo, or pname:pTexelBufferView, and must: be the same type as what was specified in sname:VkDescriptorSetLayoutBinding for pname:dstSet at pname:dstBinding. The type of the descriptor also controls which array the descriptors are taken from. pname:descriptorType can: take on values including: include::../enums/VkDescriptorType.txt[] * pname:pImageInfo points to an array of sname:VkDescriptorImageInfo structures or is ignored, as described below. * pname:pBufferInfo points to an array of sname:VkDescriptorBufferInfo structures or is ignored, as described below. * pname:pTexelBufferView points to an array of sname:VkBufferView handles or is ignored, as described below. include::../validity/structs/VkWriteDescriptorSet.txt[] Only one of pname:pImageInfo, pname:pBufferInfo, or pname:pTexelBufferView members is used according to the descriptor type specified in the pname:descriptorType member of the containing sname:VkWriteDescriptorSet structure, as specified below. If pname:descriptorType is ename:VK_DESCRIPTOR_TYPE_UNIFORM_BUFFER, ename:VK_DESCRIPTOR_TYPE_STORAGE_BUFFER, ename:VK_DESCRIPTOR_TYPE_UNIFORM_BUFFER_DYNAMIC, or ename:VK_DESCRIPTOR_TYPE_STORAGE_BUFFER_DYNAMIC, the elements of the pname:pBufferInfo array of sname:VkDescriptorBufferInfo structures will be used to update the descriptors, and other arrays will be ignored. The sname:VkDescriptorBufferInfo structure is defined as: include::../structs/VkDescriptorBufferInfo.txt[] * pname:buffer is the buffer resource. * pname:offset is the offset in bytes from the start of pname:buffer. Access to buffer memory via this descriptor uses addressing that is relative to this starting offset. * pname:range is the size in bytes that is used for this descriptor update, or ename:VK_WHOLE_SIZE to use the range from pname:offset to the end of the buffer. include::../validity/structs/VkDescriptorBufferInfo.txt[] For ename:VK_DESCRIPTOR_TYPE_UNIFORM_BUFFER_DYNAMIC and ename:VK_DESCRIPTOR_TYPE_STORAGE_BUFFER_DYNAMIC descriptor types, pname:offset is the base offset from which the dynamic offset is applied and pname:range is the static size used for all dynamic offsets. If pname:descriptorType is ename:VK_DESCRIPTOR_TYPE_UNIFORM_TEXEL_BUFFER or ename:VK_DESCRIPTOR_TYPE_STORAGE_TEXEL_BUFFER, the pname:pTexelBufferView array will be used to update the descriptors, and other arrays will be ignored. If pname:descriptorType is ename:VK_DESCRIPTOR_TYPE_SAMPLER, ename:VK_DESCRIPTOR_TYPE_COMBINED_IMAGE_SAMPLER, ename:VK_DESCRIPTOR_TYPE_SAMPLED_IMAGE, ename:VK_DESCRIPTOR_TYPE_STORAGE_IMAGE, or ename:VK_DESCRIPTOR_TYPE_INPUT_ATTACHMENT, the elements of the pname:pImageInfo array of sname:VkDescriptorImageInfo structures will be used to update the descriptors, and other arrays will be ignored. The sname:VkDescriptorImageInfo structure is defined as: include::../structs/VkDescriptorImageInfo.txt[] * pname:sampler is a sampler handle, and is used in descriptor updates for types ename:VK_DESCRIPTOR_TYPE_SAMPLER and ename:VK_DESCRIPTOR_TYPE_COMBINED_IMAGE_SAMPLER if the binding being updated does not use immutable samplers. * pname:imageView is an image view handle, and is used in descriptor updates for types ename:VK_DESCRIPTOR_TYPE_SAMPLED_IMAGE, ename:VK_DESCRIPTOR_TYPE_STORAGE_IMAGE, ename:VK_DESCRIPTOR_TYPE_COMBINED_IMAGE_SAMPLER, and ename:VK_DESCRIPTOR_TYPE_INPUT_ATTACHMENT. * pname:imageLayout is the layout that the image will be in at the time this descriptor is accessed. pname:imageLayout is used in descriptor updates for types ename:VK_DESCRIPTOR_TYPE_SAMPLED_IMAGE, ename:VK_DESCRIPTOR_TYPE_STORAGE_IMAGE, ename:VK_DESCRIPTOR_TYPE_COMBINED_IMAGE_SAMPLER, and ename:VK_DESCRIPTOR_TYPE_INPUT_ATTACHMENT. include::../validity/structs/VkDescriptorImageInfo.txt[] Members of sname:VkDescriptorImageInfo that are not used in an update (as described above) are ignored. [[descriptorsets-updates-consecutive, consecutive binding updates]] If the pname:dstBinding has fewer than pname:descriptorCount array elements remaining starting from pname:dstArrayElement, then the remainder will be used to update the subsequent binding - pname:dstBinding+1 starting at array element zero. This behavior applies recursively, with the update affecting consecutive bindings as needed to update all pname:descriptorCount descriptors. All consecutive bindings updated via a single sname:VkWriteDescriptorSet structure must: have identical pname:descriptorType and pname:stageFlags, and must: all either use immutable samplers or must: all not use immutable samplers. Each element in the pname:pDescriptorCopies array is a slink:VkCopyDescriptorSet structure describing an operation copying descriptors between sets. The sname:VkCopyDescriptorSet structure is defined as: include::../structs/VkCopyDescriptorSet.txt[] * pname:sType is the type of this structure. * pname:pNext is `NULL` or a pointer to an extension-specific structure. * pname:srcSet, pname:srcBinding, and pname:srcArrayElement are the source set, binding, and array element, respectively. * pname:dstSet, pname:dstBinding, and pname:dstArrayElement are the destination set, binding, and array element, respectively. * pname:descriptorCount is the number of descriptors to copy from the source to destination. If pname:descriptorCount is greater than the number of remaining array elements in the source or destination binding, those affect consecutive bindings in a manner similar to slink:VkWriteDescriptorSet above. include::../validity/structs/VkCopyDescriptorSet.txt[] [[descriptorsets-binding]] === Descriptor Set Binding Once descriptor sets have been allocated, one or more descriptor sets can: be bound to the command buffer by calling: include::../protos/vkCmdBindDescriptorSets.txt[] * pname:commandBuffer is the command buffer that the descriptor sets will be bound to. * pname:pipelineBindPoint is a elink:VkPipelineBindPoint indicating whether the descriptors will be used by graphics pipelines or compute pipelines. There is a separate set of bind points for each of graphics and compute, so binding one does not disturb the other. * pname:layout is a sname:VkPipelineLayout object used to program the bindings. * pname:firstSet is the set number of the first descriptor set to be bound. * pname:descriptorSetCount is the number of elements in the pname:pDescriptorSets array. * pname:pDescriptorSets is an array of handles to sname:VkDescriptorSet objects describing the descriptor sets to write to. * pname:dynamicOffsetCount is the number of dynamic offsets in the pname:pDynamicOffsets array. * pname:pDynamicOffsets is a pointer to an array of basetype:uint32_t values specifying dynamic offsets. fname:vkCmdBindDescriptorSets causes the sets numbered [pname:firstSet.. pname:firstSet+pname:descriptorSetCount-1] to use the bindings stored in pname:pDescriptorSets[0..pname:descriptorSetCount-1] for subsequent rendering commands (either compute or graphics, according to the pname:pipelineBindPoint). Any bindings that were previously applied via these sets are no longer valid. Once bound, a descriptor set affects rendering of subsequent graphics or compute commands in the command buffer until a different set is bound to the same set number, or else until the set is disturbed as described in <>. A compatible descriptor set must: be bound for all set numbers that any shaders in a pipeline access, at the time that a draw or dispatch command is recorded to execute using that pipeline. However, if none of the shaders in a pipeline statically use any bindings with a particular set number, then no descriptor set need be bound for that set number, even if the pipeline layout includes a non-trivial descriptor set layout for that set number. If any of the sets being bound include dynamic uniform or storage buffers, then pname:pDynamicOffsets includes one element for each array element in each dynamic descriptor type binding in each set. Values are taken from pname:pDynamicOffsets in an order such that all entries for set N come before set N+1; within a set, entries are ordered by the binding numbers in the descriptor set layouts; and within a binding array, elements are in order. pname:dynamicOffsetCount must: equal the total number of dynamic descriptors in the sets being bound. The effective offset used for dynamic uniform and storage buffer bindings is the sum of the relative offset taken from pname:pDynamicOffsets, and the base address of the buffer plus base offset in the descriptor set. The length of the dynamic uniform and storage buffer bindings is the buffer range as specified in the descriptor set. Each of the pname:pDescriptorSets must: be compatible with the pipeline layout specified by pname:layout. The layout used to program the bindings must: also be compatible with the pipeline used in subsequent graphics or compute commands, as defined in the <> section. The descriptor set contents bound by a call to fname:vkCmdBindDescriptorSets may: be consumed during host execution of the command, or during shader execution of the resulting draws, or any time in between. Thus, the contents mustnot: be altered (overwritten by an update command, or freed) between when the command is recorded and when the command completes executing on the queue. The contents of pname:pDynamicOffsets are consumed immediately during execution of fname:vkCmdBindDescriptorSets. Once all pending uses have completed, it is legal to update and reuse a descriptor set. include::../validity/protos/vkCmdBindDescriptorSets.txt[] === Push Constant Updates [[descriptorsets-push-constants]] As described above in section <>, the pipeline layout defines shader push constants which are updated via {apiname} commands rather than via writes to memory or copy commands. [NOTE] .Note ==== Push constants represent a high speed path to modify constant data in pipelines that is expected to outperform memory-backed resource updates. ==== The contents of the push constants are undefined at the start of a command buffer. Push constants are updated by calling: include::../protos/vkCmdPushConstants.txt[] * pname:commandBuffer is the command buffer in which the push constant update will be recorded. * pname:layout is the pipeline layout used to program the push constant updates. * pname:stageFlags is a bitmask of elink:VkShaderStageFlagBits specifying the shader stages that will use the push constants in the updated range. * pname:offset is the start offset of the push constant range to update, in units of bytes. * pname:size is the size of the push constant range to update, in units of bytes. * pname:pValues is an array of pname:size bytes containing the new push constant values. include::../validity/protos/vkCmdPushConstants.txt[]