9. Pipelines

The following figure shows a block diagram of the Vulkan pipelines. Some Vulkan commands specify geometric objects to be drawn or computational work to be performed, while others specify state controlling how objects are handled by the various pipeline stages, or control data transfer between memory organized as images and buffers. Commands are effectively sent through a processing pipeline, either a graphics pipeline or a compute pipeline.

The first stage of the graphics pipeline (Input Assembler) assembles vertices to form geometric primitives such as points, lines, and triangles, based on a requested primitive topology. In the next stage (Vertex Shader) vertices can be transformed, computing positions and attributes for each vertex. If tessellation and/or geometry shaders are supported, they can then generate multiple primitives from a single input primitive, possibly changing the primitive topology or generating additional attribute data in the process.

The final resulting primitives are clipped to a clip volume in preparation for the next stage, Rasterization. The rasterizer produces a series of framebuffer addresses and values using a two-dimensional description of a point, line segment, or triangle. Each fragment so produced is fed to the next stage (Fragment Shader) that performs operations on individual fragments before they finally alter the framebuffer. These operations include conditional updates into the framebuffer based on incoming and previously stored depth values (to effect depth buffering), blending of incoming fragment colors with stored colors, as well as masking, stenciling, and other logical operations on fragment values.

Framebuffer operations read and write the color and depth/stencil attachments of the framebuffer for a given subpass of a render pass instance. The attachments can be used as input attachments in the fragment shader in a later subpass of the same render pass.

The compute pipeline is a separate pipeline from the graphics pipeline, which operates on one-, two-, or three-dimensional workgroups which can read from and write to buffer and image memory.

This ordering is meant only as a tool for describing Vulkan, not as a strict rule of how Vulkan is implemented, and we present it only as a means to organize the various operations of the pipelines. Actual ordering guarantees between pipeline stages are explained in detail in the synchronization chapter.

image/svg+xml Vertex Shader Draw Input Assembler Tessellation Control Shader Tessellation Primitive Generator Tessellation Evaluation Shader Rasterization Indirect Buffer Descriptor Sets Legend Geometry Shader Vertex Post-Processing Early Per-Fragment Tests Fragment Shader Late Per-Fragment Tests Blending Index Buffer Vertex Buffers Push Constants Uniform Buffers Uniform Texel Buffers Sampled Images Storage Buffers Storage Texel Buffers Storage Images Compute Shader Dispatch Depth/Stencil Attachments Input Attachments Color Attachments Fixed Function Stage Shader Stage Storage Images
Figure 2. Block diagram of the Vulkan pipeline

Each pipeline is controlled by a monolithic object created from a description of all of the shader stages and any relevant fixed-function stages. Linking the whole pipeline together allows the optimization of shaders based on their input/outputs and eliminates expensive draw time state validation.

A pipeline object is bound to the current state using vkCmdBindPipeline. Any pipeline object state that is specified as dynamic is not applied to the current state when the pipeline object is bound, but is instead set by dynamic state setting commands.

No state, including dynamic state, is inherited from one command buffer to another.

Compute and graphics pipelines are each represented by VkPipeline handles:

VK_DEFINE_NON_DISPATCHABLE_HANDLE(VkPipeline)

9.1. Compute Pipelines

Compute pipelines consist of a single static compute shader stage and the pipeline layout.

The compute pipeline represents a compute shader and is created by calling vkCreateComputePipelines with module and pName selecting an entry point from a shader module, where that entry point defines a valid compute shader, in the VkPipelineShaderStageCreateInfo structure contained within the VkComputePipelineCreateInfo structure.

To create compute pipelines, call:

VkResult vkCreateComputePipelines(
    VkDevice                                    device,
    VkPipelineCache                             pipelineCache,
    uint32_t                                    createInfoCount,
    const VkComputePipelineCreateInfo*          pCreateInfos,
    const VkAllocationCallbacks*                pAllocator,
    VkPipeline*                                 pPipelines);

  • device is the logical device that creates the compute pipelines.

  • pipelineCache is either VK_NULL_HANDLE, indicating that pipeline caching is disabled; or the handle of a valid pipeline cache object, in which case use of that cache is enabled for the duration of the command.

  • createInfoCount is the length of the pCreateInfos and pPipelines arrays.

  • pCreateInfos is a pointer to an array of VkComputePipelineCreateInfo structures.

  • pAllocator controls host memory allocation as described in the Memory Allocation chapter.

  • pPipelines is a pointer to an array of VkPipeline handles in which the resulting compute pipeline objects are returned.

Valid Usage

  • If the flags member of any element of pCreateInfos contains the VK_PIPELINE_CREATE_DERIVATIVE_BIT flag, and the basePipelineIndex member of that same element is not -1, basePipelineIndex must be less than the index into pCreateInfos that corresponds to that element

  • If the flags member of any element of pCreateInfos contains the VK_PIPELINE_CREATE_DERIVATIVE_BIT flag, the base pipeline must have been created with the VK_PIPELINE_CREATE_ALLOW_DERIVATIVES_BIT flag set

Valid Usage (Implicit)

  • device must be a valid VkDevice handle

  • If pipelineCache is not VK_NULL_HANDLE, pipelineCache must be a valid VkPipelineCache handle

  • pCreateInfos must be a valid pointer to an array of createInfoCount valid VkComputePipelineCreateInfo structures

  • If pAllocator is not NULL, pAllocator must be a valid pointer to a valid VkAllocationCallbacks structure

  • pPipelines must be a valid pointer to an array of createInfoCount VkPipeline handles

  • createInfoCount must be greater than 0

  • If pipelineCache is a valid handle, it must have been created, allocated, or retrieved from device

Return Codes
Success

  • VK_SUCCESS

Failure

  • VK_ERROR_OUT_OF_HOST_MEMORY

  • VK_ERROR_OUT_OF_DEVICE_MEMORY

The VkComputePipelineCreateInfo structure is defined as:

typedef struct VkComputePipelineCreateInfo {
    VkStructureType                    sType;
    const void*                        pNext;
    VkPipelineCreateFlags              flags;
    VkPipelineShaderStageCreateInfo    stage;
    VkPipelineLayout                   layout;
    VkPipeline                         basePipelineHandle;
    int32_t                            basePipelineIndex;
} VkComputePipelineCreateInfo;

  • sType is the type of this structure.

  • pNext is NULL or a pointer to an extension-specific structure.

  • flags is a bitmask of VkPipelineCreateFlagBits specifying how the pipeline will be generated.

  • stage is a VkPipelineShaderStageCreateInfo structure describing the compute shader.

  • layout is the description of binding locations used by both the pipeline and descriptor sets used with the pipeline.

  • basePipelineHandle is a pipeline to derive from

  • basePipelineIndex is an index into the pCreateInfos parameter to use as a pipeline to derive from

The parameters basePipelineHandle and basePipelineIndex are described in more detail in Pipeline Derivatives.

Valid Usage

  • If flags contains the VK_PIPELINE_CREATE_DERIVATIVE_BIT flag, and basePipelineIndex is -1, basePipelineHandle must be a valid handle to a compute VkPipeline

  • If flags contains the VK_PIPELINE_CREATE_DERIVATIVE_BIT flag, and basePipelineHandle is VK_NULL_HANDLE, basePipelineIndex must be a valid index into the calling command’s pCreateInfos parameter

  • If flags contains the VK_PIPELINE_CREATE_DERIVATIVE_BIT flag, and basePipelineIndex is not -1, basePipelineHandle must be VK_NULL_HANDLE

  • If flags contains the VK_PIPELINE_CREATE_DERIVATIVE_BIT flag, and basePipelineHandle is not VK_NULL_HANDLE, basePipelineIndex must be -1

  • The stage member of stage must be VK_SHADER_STAGE_COMPUTE_BIT

  • The shader code for the entry point identified by stage and the rest of the state identified by this structure must adhere to the pipeline linking rules described in the Shader Interfaces chapter

  • layout must be consistent with the layout of the compute shader specified in stage

  • The number of resources in layout accessible to the compute shader stage must be less than or equal to VkPhysicalDeviceLimits::maxPerStageResources

Valid Usage (Implicit)

  • sType must be VK_STRUCTURE_TYPE_COMPUTE_PIPELINE_CREATE_INFO

  • pNext must be NULL

  • flags must be a valid combination of VkPipelineCreateFlagBits values

  • stage must be a valid VkPipelineShaderStageCreateInfo structure

  • layout must be a valid VkPipelineLayout handle

  • Both of basePipelineHandle, and layout that are valid handles of non-ignored parameters must have been created, allocated, or retrieved from the same VkDevice

The VkPipelineShaderStageCreateInfo structure is defined as:

typedef struct VkPipelineShaderStageCreateInfo {
    VkStructureType                     sType;
    const void*                         pNext;
    VkPipelineShaderStageCreateFlags    flags;
    VkShaderStageFlagBits               stage;
    VkShaderModule                      module;
    const char*                         pName;
    const VkSpecializationInfo*         pSpecializationInfo;
} VkPipelineShaderStageCreateInfo;

  • sType is the type of this structure.

  • pNext is NULL or a pointer to an extension-specific structure.

  • flags is a bitmask of VkPipelineShaderStageCreateFlagBits specifying how the pipeline shader stage will be generated.

  • stage is a VkShaderStageFlagBits value specifying a single pipeline stage.

  • module is a VkShaderModule object containing the shader for this stage.

  • pName is a pointer to a null-terminated UTF-8 string specifying the entry point name of the shader for this stage.

  • pSpecializationInfo is a pointer to a VkSpecializationInfo structure, as described in Specialization Constants, or NULL.

Valid Usage

  • If the geometry shaders feature is not enabled, stage must not be VK_SHADER_STAGE_GEOMETRY_BIT

  • If the tessellation shaders feature is not enabled, stage must not be VK_SHADER_STAGE_TESSELLATION_CONTROL_BIT or VK_SHADER_STAGE_TESSELLATION_EVALUATION_BIT

  • stage must not be VK_SHADER_STAGE_ALL_GRAPHICS, or VK_SHADER_STAGE_ALL

  • pName must be the name of an OpEntryPoint in module with an execution model that matches stage

  • If the identified entry point includes any variable in its interface that is declared with the ClipDistance BuiltIn decoration, that variable must not have an array size greater than VkPhysicalDeviceLimits::maxClipDistances

  • If the identified entry point includes any variable in its interface that is declared with the CullDistance BuiltIn decoration, that variable must not have an array size greater than VkPhysicalDeviceLimits::maxCullDistances

  • If the identified entry point includes any variables in its interface that are declared with the ClipDistance or CullDistance BuiltIn decoration, those variables must not have array sizes which sum to more than VkPhysicalDeviceLimits::maxCombinedClipAndCullDistances

  • If the identified entry point includes any variable in its interface that is declared with the SampleMask BuiltIn decoration, that variable must not have an array size greater than VkPhysicalDeviceLimits::maxSampleMaskWords

  • If stage is VK_SHADER_STAGE_VERTEX_BIT, the identified entry point must not include any input variable in its interface that is decorated with CullDistance

  • If stage is VK_SHADER_STAGE_TESSELLATION_CONTROL_BIT or VK_SHADER_STAGE_TESSELLATION_EVALUATION_BIT, and the identified entry point has an OpExecutionMode instruction that specifies a patch size with OutputVertices, the patch size must be greater than 0 and less than or equal to VkPhysicalDeviceLimits::maxTessellationPatchSize

  • If stage is VK_SHADER_STAGE_GEOMETRY_BIT, the identified entry point must have an OpExecutionMode instruction that specifies a maximum output vertex count that is greater than 0 and less than or equal to VkPhysicalDeviceLimits::maxGeometryOutputVertices

  • If stage is VK_SHADER_STAGE_GEOMETRY_BIT, the identified entry point must have an OpExecutionMode instruction that specifies an invocation count that is greater than 0 and less than or equal to VkPhysicalDeviceLimits::maxGeometryShaderInvocations

  • If stage is a vertex processing stage, and the identified entry point writes to Layer for any primitive, it must write the same value to Layer for all vertices of a given primitive

  • If stage is a vertex processing stage, and the identified entry point writes to ViewportIndex for any primitive, it must write the same value to ViewportIndex for all vertices of a given primitive

  • If stage is VK_SHADER_STAGE_FRAGMENT_BIT, the identified entry point must not include any output variables in its interface decorated with CullDistance

  • If stage is VK_SHADER_STAGE_FRAGMENT_BIT, and the identified entry point writes to FragDepth in any execution path, it must write to FragDepth in all execution paths

Valid Usage (Implicit)

  • sType must be VK_STRUCTURE_TYPE_PIPELINE_SHADER_STAGE_CREATE_INFO

  • pNext must be NULL

  • flags must be 0

  • stage must be a valid VkShaderStageFlagBits value

  • module must be a valid VkShaderModule handle

  • pName must be a null-terminated UTF-8 string

  • If pSpecializationInfo is not NULL, pSpecializationInfo must be a valid pointer to a valid VkSpecializationInfo structure

typedef VkFlags VkPipelineShaderStageCreateFlags;

VkPipelineShaderStageCreateFlags is a bitmask type for setting a mask of zero or more VkPipelineShaderStageCreateFlagBits.

Possible values of the flags member of VkPipelineShaderStageCreateInfo specifying how a pipeline shader stage is created, are:

typedef enum VkPipelineShaderStageCreateFlagBits {
    VK_PIPELINE_SHADER_STAGE_CREATE_FLAG_BITS_MAX_ENUM = 0x7FFFFFFF
} VkPipelineShaderStageCreateFlagBits;

Commands and structures which need to specify one or more shader stages do so using a bitmask whose bits correspond to stages. Bits which can be set to specify shader stages are:

typedef enum VkShaderStageFlagBits {
    VK_SHADER_STAGE_VERTEX_BIT = 0x00000001,
    VK_SHADER_STAGE_TESSELLATION_CONTROL_BIT = 0x00000002,
    VK_SHADER_STAGE_TESSELLATION_EVALUATION_BIT = 0x00000004,
    VK_SHADER_STAGE_GEOMETRY_BIT = 0x00000008,
    VK_SHADER_STAGE_FRAGMENT_BIT = 0x00000010,
    VK_SHADER_STAGE_COMPUTE_BIT = 0x00000020,
    VK_SHADER_STAGE_ALL_GRAPHICS = 0x0000001F,
    VK_SHADER_STAGE_ALL = 0x7FFFFFFF,
    VK_SHADER_STAGE_FLAG_BITS_MAX_ENUM = 0x7FFFFFFF
} VkShaderStageFlagBits;

  • VK_SHADER_STAGE_VERTEX_BIT specifies the vertex stage.

  • VK_SHADER_STAGE_TESSELLATION_CONTROL_BIT specifies the tessellation control stage.

  • VK_SHADER_STAGE_TESSELLATION_EVALUATION_BIT specifies the tessellation evaluation stage.

  • VK_SHADER_STAGE_GEOMETRY_BIT specifies the geometry stage.

  • VK_SHADER_STAGE_FRAGMENT_BIT specifies the fragment stage.

  • VK_SHADER_STAGE_COMPUTE_BIT specifies the compute stage.

  • VK_SHADER_STAGE_ALL_GRAPHICS is a combination of bits used as shorthand to specify all graphics stages defined above (excluding the compute stage).

  • VK_SHADER_STAGE_ALL is a combination of bits used as shorthand to specify all shader stages supported by the device, including all additional stages which are introduced by extensions.

Note

VK_SHADER_STAGE_ALL_GRAPHICS only includes the original five graphics stages included in Vulkan 1.0, and not any stages added by extensions. Thus, it may not have the desired effect in all cases.

 
typedef VkFlags VkShaderStageFlags;

VkShaderStageFlags is a bitmask type for setting a mask of zero or more VkShaderStageFlagBits.

9.2. Graphics Pipelines

Graphics pipelines consist of multiple shader stages, multiple fixed-function pipeline stages, and a pipeline layout.

To create graphics pipelines, call:

VkResult vkCreateGraphicsPipelines(
    VkDevice                                    device,
    VkPipelineCache                             pipelineCache,
    uint32_t                                    createInfoCount,
    const VkGraphicsPipelineCreateInfo*         pCreateInfos,
    const VkAllocationCallbacks*                pAllocator,
    VkPipeline*                                 pPipelines);

  • device is the logical device that creates the graphics pipelines.

  • pipelineCache is either VK_NULL_HANDLE, indicating that pipeline caching is disabled; or the handle of a valid pipeline cache object, in which case use of that cache is enabled for the duration of the command.

  • createInfoCount is the length of the pCreateInfos and pPipelines arrays.

  • pCreateInfos is a pointer to an array of VkGraphicsPipelineCreateInfo structures.

  • pAllocator controls host memory allocation as described in the Memory Allocation chapter.

  • pPipelines is a pointer to an array of VkPipeline handles in which the resulting graphics pipeline objects are returned.

The VkGraphicsPipelineCreateInfo structure includes an array of shader create info structures containing all the desired active shader stages, as well as creation info to define all relevant fixed-function stages, and a pipeline layout.

Valid Usage

  • If the flags member of any element of pCreateInfos contains the VK_PIPELINE_CREATE_DERIVATIVE_BIT flag, and the basePipelineIndex member of that same element is not -1, basePipelineIndex must be less than the index into pCreateInfos that corresponds to that element

  • If the flags member of any element of pCreateInfos contains the VK_PIPELINE_CREATE_DERIVATIVE_BIT flag, the base pipeline must have been created with the VK_PIPELINE_CREATE_ALLOW_DERIVATIVES_BIT flag set

Valid Usage (Implicit)

  • device must be a valid VkDevice handle

  • If pipelineCache is not VK_NULL_HANDLE, pipelineCache must be a valid VkPipelineCache handle

  • pCreateInfos must be a valid pointer to an array of createInfoCount valid VkGraphicsPipelineCreateInfo structures

  • If pAllocator is not NULL, pAllocator must be a valid pointer to a valid VkAllocationCallbacks structure

  • pPipelines must be a valid pointer to an array of createInfoCount VkPipeline handles

  • createInfoCount must be greater than 0

  • If pipelineCache is a valid handle, it must have been created, allocated, or retrieved from device

Return Codes
Success

  • VK_SUCCESS

Failure

  • VK_ERROR_OUT_OF_HOST_MEMORY

  • VK_ERROR_OUT_OF_DEVICE_MEMORY

The VkGraphicsPipelineCreateInfo structure is defined as:

typedef struct VkGraphicsPipelineCreateInfo {
    VkStructureType                                  sType;
    const void*                                      pNext;
    VkPipelineCreateFlags                            flags;
    uint32_t                                         stageCount;
    const VkPipelineShaderStageCreateInfo*           pStages;
    const VkPipelineVertexInputStateCreateInfo*      pVertexInputState;
    const VkPipelineInputAssemblyStateCreateInfo*    pInputAssemblyState;
    const VkPipelineTessellationStateCreateInfo*     pTessellationState;
    const VkPipelineViewportStateCreateInfo*         pViewportState;
    const VkPipelineRasterizationStateCreateInfo*    pRasterizationState;
    const VkPipelineMultisampleStateCreateInfo*      pMultisampleState;
    const VkPipelineDepthStencilStateCreateInfo*     pDepthStencilState;
    const VkPipelineColorBlendStateCreateInfo*       pColorBlendState;
    const VkPipelineDynamicStateCreateInfo*          pDynamicState;
    VkPipelineLayout                                 layout;
    VkRenderPass                                     renderPass;
    uint32_t                                         subpass;
    VkPipeline                                       basePipelineHandle;
    int32_t                                          basePipelineIndex;
} VkGraphicsPipelineCreateInfo;

  • sType is the type of this structure.

  • pNext is NULL or a pointer to an extension-specific structure.

  • flags is a bitmask of VkPipelineCreateFlagBits specifying how the pipeline will be generated.

  • stageCount is the number of entries in the pStages array.

  • pStages is a pointer to an array of stageCount VkPipelineShaderStageCreateInfo structures describing the set of the shader stages to be included in the graphics pipeline.

  • pVertexInputState is a pointer to a VkPipelineVertexInputStateCreateInfo structure.

  • pInputAssemblyState is a pointer to a VkPipelineInputAssemblyStateCreateInfo structure which determines input assembly behavior, as described in Drawing Commands.

  • pTessellationState is a pointer to a VkPipelineTessellationStateCreateInfo structure, and is ignored if the pipeline does not include a tessellation control shader stage and tessellation evaluation shader stage.

  • pViewportState is a pointer to a VkPipelineViewportStateCreateInfo structure, and is ignored if the pipeline has rasterization disabled.

  • pRasterizationState is a pointer to a VkPipelineRasterizationStateCreateInfo structure.

  • pMultisampleState is a pointer to a VkPipelineMultisampleStateCreateInfo structure, and is ignored if the pipeline has rasterization disabled.

  • pDepthStencilState is a pointer to a VkPipelineDepthStencilStateCreateInfo structure, and is ignored if the pipeline has rasterization disabled or if the subpass of the render pass the pipeline is created against does not use a depth/stencil attachment.

  • pColorBlendState is a pointer to a VkPipelineColorBlendStateCreateInfo structure, and is ignored if the pipeline has rasterization disabled or if the subpass of the render pass the pipeline is created against does not use any color attachments.

  • pDynamicState is a pointer to a VkPipelineDynamicStateCreateInfo structure, and is used to indicate which properties of the pipeline state object are dynamic and can be changed independently of the pipeline state. This can be NULL, which means no state in the pipeline is considered dynamic.

  • layout is the description of binding locations used by both the pipeline and descriptor sets used with the pipeline.

  • renderPass is a handle to a render pass object describing the environment in which the pipeline will be used; the pipeline must only be used with an instance of any render pass compatible with the one provided. See Render Pass Compatibility for more information.

  • subpass is the index of the subpass in the render pass where this pipeline will be used.

  • basePipelineHandle is a pipeline to derive from.

  • basePipelineIndex is an index into the pCreateInfos parameter to use as a pipeline to derive from.

The parameters basePipelineHandle and basePipelineIndex are described in more detail in Pipeline Derivatives.

Valid Usage

  • If flags contains the VK_PIPELINE_CREATE_DERIVATIVE_BIT flag, and basePipelineIndex is -1, basePipelineHandle must be a valid handle to a graphics VkPipeline

  • If flags contains the VK_PIPELINE_CREATE_DERIVATIVE_BIT flag, and basePipelineHandle is VK_NULL_HANDLE, basePipelineIndex must be a valid index into the calling command’s pCreateInfos parameter

  • If flags contains the VK_PIPELINE_CREATE_DERIVATIVE_BIT flag, and basePipelineIndex is not -1, basePipelineHandle must be VK_NULL_HANDLE

  • If flags contains the VK_PIPELINE_CREATE_DERIVATIVE_BIT flag, and basePipelineHandle is not VK_NULL_HANDLE, basePipelineIndex must be -1

  • The stage member of each element of pStages must be unique

  • The stage member of one element of pStages must be VK_SHADER_STAGE_VERTEX_BIT

  • The stage member of each element of pStages must not be VK_SHADER_STAGE_COMPUTE_BIT

  • If pStages includes a tessellation control shader stage, it must include a tessellation evaluation shader stage

  • If pStages includes a tessellation evaluation shader stage, it must include a tessellation control shader stage

  • If pStages includes a tessellation control shader stage and a tessellation evaluation shader stage, pTessellationState must be a valid pointer to a valid VkPipelineTessellationStateCreateInfo structure

  • If pStages includes tessellation shader stages, the shader code of at least one stage must contain an OpExecutionMode instruction that specifies the type of subdivision in the pipeline

  • If pStages includes tessellation shader stages, and the shader code of both stages contain an OpExecutionMode instruction that specifies the type of subdivision in the pipeline, they must both specify the same subdivision mode

  • If pStages includes tessellation shader stages, the shader code of at least one stage must contain an OpExecutionMode instruction that specifies the output patch size in the pipeline

  • If pStages includes tessellation shader stages, and the shader code of both contain an OpExecutionMode instruction that specifies the out patch size in the pipeline, they must both specify the same patch size

  • If pStages includes tessellation shader stages, the topology member of pInputAssembly must be VK_PRIMITIVE_TOPOLOGY_PATCH_LIST

  • If the topology member of pInputAssembly is VK_PRIMITIVE_TOPOLOGY_PATCH_LIST, pStages must include tessellation shader stages

  • If pStages includes a geometry shader stage, and does not include any tessellation shader stages, its shader code must contain an OpExecutionMode instruction that specifies an input primitive type that is compatible with the primitive topology specified in pInputAssembly

  • If pStages includes a geometry shader stage, and also includes tessellation shader stages, its shader code must contain an OpExecutionMode instruction that specifies an input primitive type that is compatible with the primitive topology that is output by the tessellation stages

  • If pStages includes a fragment shader stage and a geometry shader stage, and the fragment shader code reads from an input variable that is decorated with PrimitiveID, then the geometry shader code must write to a matching output variable, decorated with PrimitiveID, in all execution paths

  • If pStages includes a fragment shader stage, its shader code must not read from any input attachment that is defined as VK_ATTACHMENT_UNUSED in subpass

  • The shader code for the entry points identified by pStages, and the rest of the state identified by this structure must adhere to the pipeline linking rules described in the Shader Interfaces chapter

  • If rasterization is not disabled and subpass uses a depth/stencil attachment in renderPass that has a layout of VK_IMAGE_LAYOUT_DEPTH_STENCIL_READ_ONLY_OPTIMAL in the VkAttachmentReference defined by subpass, the depthWriteEnable member of pDepthStencilState must be VK_FALSE

  • If rasterization is not disabled and subpass uses a depth/stencil attachment in renderPass that has a layout of VK_IMAGE_LAYOUT_DEPTH_STENCIL_READ_ONLY_OPTIMAL in the VkAttachmentReference defined by subpass, the failOp, passOp and depthFailOp members of each of the front and back members of pDepthStencilState must be VK_STENCIL_OP_KEEP

  • If rasterization is not disabled and the subpass uses color attachments, then for each color attachment in the subpass the blendEnable member of the corresponding element of the pAttachment member of pColorBlendState must be VK_FALSE if the attached image’s format features does not contain VK_FORMAT_FEATURE_COLOR_ATTACHMENT_BLEND_BIT.

  • If rasterization is not disabled and the subpass uses color attachments, the attachmentCount member of pColorBlendState must be equal to the colorAttachmentCount used to create subpass

  • If no element of the pDynamicStates member of pDynamicState is VK_DYNAMIC_STATE_VIEWPORT, the pViewports member of pViewportState must be a valid pointer to an array of pViewportState->viewportCount valid VkViewport structures

  • If no element of the pDynamicStates member of pDynamicState is VK_DYNAMIC_STATE_SCISSOR, the pScissors member of pViewportState must be a valid pointer to an array of pViewportState->scissorCount VkRect2D structures

  • If the wide lines feature is not enabled, and no element of the pDynamicStates member of pDynamicState is VK_DYNAMIC_STATE_LINE_WIDTH, the lineWidth member of pRasterizationState must be 1.0

  • If the rasterizerDiscardEnable member of pRasterizationState is VK_FALSE, pViewportState must be a valid pointer to a valid VkPipelineViewportStateCreateInfo structure

  • If the rasterizerDiscardEnable member of pRasterizationState is VK_FALSE, pMultisampleState must be a valid pointer to a valid VkPipelineMultisampleStateCreateInfo structure

  • If the rasterizerDiscardEnable member of pRasterizationState is VK_FALSE, and subpass uses a depth/stencil attachment, pDepthStencilState must be a valid pointer to a valid VkPipelineDepthStencilStateCreateInfo structure

  • If the rasterizerDiscardEnable member of pRasterizationState is VK_FALSE, and subpass uses color attachments, pColorBlendState must be a valid pointer to a valid VkPipelineColorBlendStateCreateInfo structure

  • If the depth bias clamping feature is not enabled, no element of the pDynamicStates member of pDynamicState is VK_DYNAMIC_STATE_DEPTH_BIAS, and the depthBiasEnable member of pRasterizationState is VK_TRUE, the depthBiasClamp member of pRasterizationState must be 0.0

  • If no element of the pDynamicStates member of pDynamicState is VK_DYNAMIC_STATE_DEPTH_BOUNDS, and the depthBoundsTestEnable member of pDepthStencilState is VK_TRUE, the minDepthBounds and maxDepthBounds members of pDepthStencilState must be between 0.0 and 1.0, inclusive

  • layout must be consistent with all shaders specified in pStages

  • If neither the VK_AMD_mixed_attachment_samples nor the VK_NV_framebuffer_mixed_samples extensions are enabled, and if subpass uses color and/or depth/stencil attachments, then the rasterizationSamples member of pMultisampleState must be the same as the sample count for those subpass attachments

  • If subpass does not use any color and/or depth/stencil attachments, then the rasterizationSamples member of pMultisampleState must follow the rules for a zero-attachment subpass

  • subpass must be a valid subpass within renderPass

  • The number of resources in layout accessible to each shader stage that is used by the pipeline must be less than or equal to VkPhysicalDeviceLimits::maxPerStageResources

  • If pStages includes a vertex shader stage, pVertexInputState must be a valid pointer to a valid VkPipelineVertexInputStateCreateInfo structure

  • If pStages includes a vertex shader stage, pInputAssemblyState must be a valid pointer to a valid VkPipelineInputAssemblyStateCreateInfo structure

Valid Usage (Implicit)

Possible values of the flags member of VkGraphicsPipelineCreateInfo and VkComputePipelineCreateInfo, specifying how a pipeline is created, are:

typedef enum VkPipelineCreateFlagBits {
    VK_PIPELINE_CREATE_DISABLE_OPTIMIZATION_BIT = 0x00000001,
    VK_PIPELINE_CREATE_ALLOW_DERIVATIVES_BIT = 0x00000002,
    VK_PIPELINE_CREATE_DERIVATIVE_BIT = 0x00000004,
    VK_PIPELINE_CREATE_FLAG_BITS_MAX_ENUM = 0x7FFFFFFF
} VkPipelineCreateFlagBits;

  • VK_PIPELINE_CREATE_DISABLE_OPTIMIZATION_BIT specifies that the created pipeline will not be optimized. Using this flag may reduce the time taken to create the pipeline.

  • VK_PIPELINE_CREATE_ALLOW_DERIVATIVES_BIT specifies that the pipeline to be created is allowed to be the parent of a pipeline that will be created in a subsequent call to vkCreateGraphicsPipelines or vkCreateComputePipelines.

  • VK_PIPELINE_CREATE_DERIVATIVE_BIT specifies that the pipeline to be created will be a child of a previously created parent pipeline.

It is valid to set both VK_PIPELINE_CREATE_ALLOW_DERIVATIVES_BIT and VK_PIPELINE_CREATE_DERIVATIVE_BIT. This allows a pipeline to be both a parent and possibly a child in a pipeline hierarchy. See Pipeline Derivatives for more information.

typedef VkFlags VkPipelineCreateFlags;

VkPipelineCreateFlags is a bitmask type for setting a mask of zero or more VkPipelineCreateFlagBits.

The VkPipelineDynamicStateCreateInfo structure is defined as:

typedef struct VkPipelineDynamicStateCreateInfo {
    VkStructureType                      sType;
    const void*                          pNext;
    VkPipelineDynamicStateCreateFlags    flags;
    uint32_t                             dynamicStateCount;
    const VkDynamicState*                pDynamicStates;
} VkPipelineDynamicStateCreateInfo;

  • sType is the type of this structure.

  • pNext is NULL or a pointer to an extension-specific structure.

  • flags is reserved for future use.

  • dynamicStateCount is the number of elements in the pDynamicStates array.

  • pDynamicStates is a pointer to an array of VkDynamicState values specifying which pieces of pipeline state will use the values from dynamic state commands rather than from pipeline state creation info.

Valid Usage

  • Each element of pDynamicStates must be unique

Valid Usage (Implicit)

  • sType must be VK_STRUCTURE_TYPE_PIPELINE_DYNAMIC_STATE_CREATE_INFO

  • pNext must be NULL

  • flags must be 0

  • If dynamicStateCount is not 0, pDynamicStates must be a valid pointer to an array of dynamicStateCount valid VkDynamicState values

typedef VkFlags VkPipelineDynamicStateCreateFlags;

VkPipelineDynamicStateCreateFlags is a bitmask type for setting a mask, but is currently reserved for future use.

The source of different pieces of dynamic state is specified by the VkPipelineDynamicStateCreateInfo::pDynamicStates property of the currently active pipeline, each of whose elements must be one of the values:

typedef enum VkDynamicState {
    VK_DYNAMIC_STATE_VIEWPORT = 0,
    VK_DYNAMIC_STATE_SCISSOR = 1,
    VK_DYNAMIC_STATE_LINE_WIDTH = 2,
    VK_DYNAMIC_STATE_DEPTH_BIAS = 3,
    VK_DYNAMIC_STATE_BLEND_CONSTANTS = 4,
    VK_DYNAMIC_STATE_DEPTH_BOUNDS = 5,
    VK_DYNAMIC_STATE_STENCIL_COMPARE_MASK = 6,
    VK_DYNAMIC_STATE_STENCIL_WRITE_MASK = 7,
    VK_DYNAMIC_STATE_STENCIL_REFERENCE = 8,
    VK_DYNAMIC_STATE_MAX_ENUM = 0x7FFFFFFF
} VkDynamicState;

  • VK_DYNAMIC_STATE_VIEWPORT specifies that the pViewports state in VkPipelineViewportStateCreateInfo will be ignored and must be set dynamically with vkCmdSetViewport before any draw commands. The number of viewports used by a pipeline is still specified by the viewportCount member of VkPipelineViewportStateCreateInfo.

  • VK_DYNAMIC_STATE_SCISSOR specifies that the pScissors state in VkPipelineViewportStateCreateInfo will be ignored and must be set dynamically with vkCmdSetScissor before any draw commands. The number of scissor rectangles used by a pipeline is still specified by the scissorCount member of VkPipelineViewportStateCreateInfo.

  • VK_DYNAMIC_STATE_LINE_WIDTH specifies that the lineWidth state in VkPipelineRasterizationStateCreateInfo will be ignored and must be set dynamically with vkCmdSetLineWidth before any draw commands that generate line primitives for the rasterizer.

  • VK_DYNAMIC_STATE_DEPTH_BIAS specifies that the depthBiasConstantFactor, depthBiasClamp and depthBiasSlopeFactor states in VkPipelineRasterizationStateCreateInfo will be ignored and must be set dynamically with vkCmdSetDepthBias before any draws are performed with depthBiasEnable in VkPipelineRasterizationStateCreateInfo set to VK_TRUE.

  • VK_DYNAMIC_STATE_BLEND_CONSTANTS specifies that the blendConstants state in VkPipelineColorBlendStateCreateInfo will be ignored and must be set dynamically with vkCmdSetBlendConstants before any draws are performed with a pipeline state with VkPipelineColorBlendAttachmentState member blendEnable set to VK_TRUE and any of the blend functions using a constant blend color.

  • VK_DYNAMIC_STATE_DEPTH_BOUNDS specifies that the minDepthBounds and maxDepthBounds states of VkPipelineDepthStencilStateCreateInfo will be ignored and must be set dynamically with vkCmdSetDepthBounds before any draws are performed with a pipeline state with VkPipelineDepthStencilStateCreateInfo member depthBoundsTestEnable set to VK_TRUE.

  • VK_DYNAMIC_STATE_STENCIL_COMPARE_MASK specifies that the compareMask state in VkPipelineDepthStencilStateCreateInfo for both front and back will be ignored and must be set dynamically with vkCmdSetStencilCompareMask before any draws are performed with a pipeline state with VkPipelineDepthStencilStateCreateInfo member stencilTestEnable set to VK_TRUE

  • VK_DYNAMIC_STATE_STENCIL_WRITE_MASK specifies that the writeMask state in VkPipelineDepthStencilStateCreateInfo for both front and back will be ignored and must be set dynamically with vkCmdSetStencilWriteMask before any draws are performed with a pipeline state with VkPipelineDepthStencilStateCreateInfo member stencilTestEnable set to VK_TRUE

  • VK_DYNAMIC_STATE_STENCIL_REFERENCE specifies that the reference state in VkPipelineDepthStencilStateCreateInfo for both front and back will be ignored and must be set dynamically with vkCmdSetStencilReference before any draws are performed with a pipeline state with VkPipelineDepthStencilStateCreateInfo member stencilTestEnable set to VK_TRUE

9.2.1. Valid Combinations of Stages for Graphics Pipelines

If tessellation shader stages are omitted, the tessellation shading and fixed-function stages of the pipeline are skipped.

If a geometry shader is omitted, the geometry shading stage is skipped.

If a fragment shader is omitted, fragment color outputs have undefined values, and the fragment depth value is unmodified. This can be useful for depth-only rendering.

Presence of a shader stage in a pipeline is indicated by including a valid VkPipelineShaderStageCreateInfo with module and pName selecting an entry point from a shader module, where that entry point is valid for the stage specified by stage.

Presence of some of the fixed-function stages in the pipeline is implicitly derived from enabled shaders and provided state. For example, the fixed-function tessellator is always present when the pipeline has valid Tessellation Control and Tessellation Evaluation shaders.

For example:

9.3. Pipeline destruction

To destroy a graphics or compute pipeline, call:

void vkDestroyPipeline(
    VkDevice                                    device,
    VkPipeline                                  pipeline,
    const VkAllocationCallbacks*                pAllocator);

  • device is the logical device that destroys the pipeline.

  • pipeline is the handle of the pipeline to destroy.

  • pAllocator controls host memory allocation as described in the Memory Allocation chapter.

Valid Usage

  • All submitted commands that refer to pipeline must have completed execution

  • If VkAllocationCallbacks were provided when pipeline was created, a compatible set of callbacks must be provided here

  • If no VkAllocationCallbacks were provided when pipeline was created, pAllocator must be NULL

Valid Usage (Implicit)

  • device must be a valid VkDevice handle

  • If pipeline is not VK_NULL_HANDLE, pipeline must be a valid VkPipeline handle

  • If pAllocator is not NULL, pAllocator must be a valid pointer to a valid VkAllocationCallbacks structure

  • If pipeline is a valid handle, it must have been created, allocated, or retrieved from device

Host Synchronization

  • Host access to pipeline must be externally synchronized

9.4. Multiple Pipeline Creation

Multiple pipelines can be created simultaneously by passing an array of VkGraphicsPipelineCreateInfo or VkComputePipelineCreateInfo structures into the vkCreateGraphicsPipelines and vkCreateComputePipelines commands, respectively. Applications can group together similar pipelines to be created in a single call, and implementations are encouraged to look for reuse opportunities within a group-create.

When an application attempts to create many pipelines in a single command, it is possible that some subset may fail creation. In that case, the corresponding entries in the pPipelines output array will be filled with VK_NULL_HANDLE values. If any pipeline fails creation (for example, due to out of memory errors), the vkCreate*Pipelines commands will return an error code. The implementation will attempt to create all pipelines, and only return VK_NULL_HANDLE values for those that actually failed.

9.5. Pipeline Derivatives

A pipeline derivative is a child pipeline created from a parent pipeline, where the child and parent are expected to have much commonality. The goal of derivative pipelines is that they be cheaper to create using the parent as a starting point, and that it be more efficient (on either host or device) to switch/bind between children of the same parent.

A derivative pipeline is created by setting the VK_PIPELINE_CREATE_DERIVATIVE_BIT flag in the Vk*PipelineCreateInfo structure. If this is set, then exactly one of basePipelineHandle or basePipelineIndex members of the structure must have a valid handle/index, and specifies the parent pipeline. If basePipelineHandle is used, the parent pipeline must have already been created. If basePipelineIndex is used, then the parent is being created in the same command. VK_NULL_HANDLE acts as the invalid handle for basePipelineHandle, and -1 is the invalid index for basePipelineIndex. If basePipelineIndex is used, the base pipeline must appear earlier in the array. The base pipeline must have been created with the VK_PIPELINE_CREATE_ALLOW_DERIVATIVES_BIT flag set.

9.6. Pipeline Cache

Pipeline cache objects allow the result of pipeline construction to be reused between pipelines and between runs of an application. Reuse between pipelines is achieved by passing the same pipeline cache object when creating multiple related pipelines. Reuse across runs of an application is achieved by retrieving pipeline cache contents in one run of an application, saving the contents, and using them to preinitialize a pipeline cache on a subsequent run. The contents of the pipeline cache objects are managed by the implementation. Applications can manage the host memory consumed by a pipeline cache object and control the amount of data retrieved from a pipeline cache object.

Pipeline cache objects are represented by VkPipelineCache handles:

VK_DEFINE_NON_DISPATCHABLE_HANDLE(VkPipelineCache)

To create pipeline cache objects, call:

VkResult vkCreatePipelineCache(
    VkDevice                                    device,
    const VkPipelineCacheCreateInfo*            pCreateInfo,
    const VkAllocationCallbacks*                pAllocator,
    VkPipelineCache*                            pPipelineCache);

  • device is the logical device that creates the pipeline cache object.

  • pCreateInfo is a pointer to a VkPipelineCacheCreateInfo structure containing initial parameters for the pipeline cache object.

  • pAllocator controls host memory allocation as described in the Memory Allocation chapter.

  • pPipelineCache is a pointer to a VkPipelineCache handle in which the resulting pipeline cache object is returned.

Note

Applications can track and manage the total host memory size of a pipeline cache object using the pAllocator. Applications can limit the amount of data retrieved from a pipeline cache object in vkGetPipelineCacheData. Implementations should not internally limit the total number of entries added to a pipeline cache object or the total host memory consumed.

Once created, a pipeline cache can be passed to the vkCreateGraphicsPipelines and vkCreateComputePipelines commands. If the pipeline cache passed into these commands is not VK_NULL_HANDLE, the implementation will query it for possible reuse opportunities and update it with new content. The use of the pipeline cache object in these commands is internally synchronized, and the same pipeline cache object can be used in multiple threads simultaneously.

Note

Implementations should make every effort to limit any critical sections to the actual accesses to the cache, which is expected to be significantly shorter than the duration of the vkCreateGraphicsPipelines and vkCreateComputePipelines commands.
Valid Usage (Implicit)
Return Codes
Success

  • VK_SUCCESS

Failure

  • VK_ERROR_OUT_OF_HOST_MEMORY

  • VK_ERROR_OUT_OF_DEVICE_MEMORY

The VkPipelineCacheCreateInfo structure is defined as:

typedef struct VkPipelineCacheCreateInfo {
    VkStructureType               sType;
    const void*                   pNext;
    VkPipelineCacheCreateFlags    flags;
    size_t                        initialDataSize;
    const void*                   pInitialData;
} VkPipelineCacheCreateInfo;

  • sType is the type of this structure.

  • pNext is NULL or a pointer to an extension-specific structure.

  • flags is reserved for future use.

  • initialDataSize is the number of bytes in pInitialData. If initialDataSize is zero, the pipeline cache will initially be empty.

  • pInitialData is a pointer to previously retrieved pipeline cache data. If the pipeline cache data is incompatible (as defined below) with the device, the pipeline cache will be initially empty. If initialDataSize is zero, pInitialData is ignored.

Valid Usage

  • If initialDataSize is not 0, it must be equal to the size of pInitialData, as returned by vkGetPipelineCacheData when pInitialData was originally retrieved

  • If initialDataSize is not 0, pInitialData must have been retrieved from a previous call to vkGetPipelineCacheData

Valid Usage (Implicit)

  • sType must be VK_STRUCTURE_TYPE_PIPELINE_CACHE_CREATE_INFO

  • pNext must be NULL

  • flags must be 0

  • If initialDataSize is not 0, pInitialData must be a valid pointer to an array of initialDataSize bytes

typedef VkFlags VkPipelineCacheCreateFlags;

VkPipelineCacheCreateFlags is a bitmask type for setting a mask, but is currently reserved for future use.

Pipeline cache objects can be merged using the command:

VkResult vkMergePipelineCaches(
    VkDevice                                    device,
    VkPipelineCache                             dstCache,
    uint32_t                                    srcCacheCount,
    const VkPipelineCache*                      pSrcCaches);

  • device is the logical device that owns the pipeline cache objects.

  • dstCache is the handle of the pipeline cache to merge results into.

  • srcCacheCount is the length of the pSrcCaches array.

  • pSrcCaches is a pointer to an array of pipeline cache handles, which will be merged into dstCache. The previous contents of dstCache are included after the merge.

Note

The details of the merge operation are implementation dependent, but implementations should merge the contents of the specified pipelines and prune duplicate entries.
Valid Usage

  • dstCache must not appear in the list of source caches

Valid Usage (Implicit)

  • device must be a valid VkDevice handle

  • dstCache must be a valid VkPipelineCache handle

  • pSrcCaches must be a valid pointer to an array of srcCacheCount valid VkPipelineCache handles

  • srcCacheCount must be greater than 0

  • dstCache must have been created, allocated, or retrieved from device

  • Each element of pSrcCaches must have been created, allocated, or retrieved from device

Host Synchronization

  • Host access to dstCache must be externally synchronized

Return Codes
Success

  • VK_SUCCESS

Failure

  • VK_ERROR_OUT_OF_HOST_MEMORY

  • VK_ERROR_OUT_OF_DEVICE_MEMORY

Data can be retrieved from a pipeline cache object using the command:

VkResult vkGetPipelineCacheData(
    VkDevice                                    device,
    VkPipelineCache                             pipelineCache,
    size_t*                                     pDataSize,
    void*                                       pData);

  • device is the logical device that owns the pipeline cache.

  • pipelineCache is the pipeline cache to retrieve data from.

  • pDataSize is a pointer to a size_t value related to the amount of data in the pipeline cache, as described below.

  • pData is either NULL or a pointer to a buffer.

If pData is NULL, then the maximum size of the data that can be retrieved from the pipeline cache, in bytes, is returned in pDataSize. Otherwise, pDataSize must point to a variable set by the user to the size of the buffer, in bytes, pointed to by pData, and on return the variable is overwritten with the amount of data actually written to pData.

If pDataSize is less than the maximum size that can be retrieved by the pipeline cache, at most pDataSize bytes will be written to pData, and vkGetPipelineCacheData will return VK_INCOMPLETE. Any data written to pData is valid and can be provided as the pInitialData member of the VkPipelineCacheCreateInfo structure passed to vkCreatePipelineCache.

Two calls to vkGetPipelineCacheData with the same parameters must retrieve the same data unless a command that modifies the contents of the cache is called between them.

Applications can store the data retrieved from the pipeline cache, and use these data, possibly in a future run of the application, to populate new pipeline cache objects. The results of pipeline compiles, however, may depend on the vendor ID, device ID, driver version, and other details of the device. To enable applications to detect when previously retrieved data is incompatible with the device, the initial bytes written to pData must be a header consisting of the following members:

Table 7. Layout for pipeline cache header version VK_PIPELINE_CACHE_HEADER_VERSION_ONE
Offset Size Meaning

0

4

length in bytes of the entire pipeline cache header written as a stream of bytes, with the least significant byte first

4

4

a VkPipelineCacheHeaderVersion value written as a stream of bytes, with the least significant byte first

8

4

a vendor ID equal to VkPhysicalDeviceProperties::vendorID written as a stream of bytes, with the least significant byte first

12

4

a device ID equal to VkPhysicalDeviceProperties::deviceID written as a stream of bytes, with the least significant byte first

16

VK_UUID_SIZE

a pipeline cache ID equal to VkPhysicalDeviceProperties::pipelineCacheUUID

The first four bytes encode the length of the entire pipeline cache header, in bytes. This value includes all fields in the header including the pipeline cache version field and the size of the length field.

The next four bytes encode the pipeline cache version, as described for VkPipelineCacheHeaderVersion. A consumer of the pipeline cache should use the cache version to interpret the remainder of the cache header.

If pDataSize is less than what is necessary to store this header, nothing will be written to pData and zero will be written to pDataSize.

Valid Usage (Implicit)

  • device must be a valid VkDevice handle

  • pipelineCache must be a valid VkPipelineCache handle

  • pDataSize must be a valid pointer to a size_t value

  • If the value referenced by pDataSize is not 0, and pData is not NULL, pData must be a valid pointer to an array of pDataSize bytes

  • pipelineCache must have been created, allocated, or retrieved from device

Return Codes
Success

  • VK_SUCCESS

  • VK_INCOMPLETE

Failure

  • VK_ERROR_OUT_OF_HOST_MEMORY

  • VK_ERROR_OUT_OF_DEVICE_MEMORY

Possible values of the second group of four bytes in the header returned by vkGetPipelineCacheData, encoding the pipeline cache version, are:

typedef enum VkPipelineCacheHeaderVersion {
    VK_PIPELINE_CACHE_HEADER_VERSION_ONE = 1,
    VK_PIPELINE_CACHE_HEADER_VERSION_MAX_ENUM = 0x7FFFFFFF
} VkPipelineCacheHeaderVersion;

  • VK_PIPELINE_CACHE_HEADER_VERSION_ONE specifies version one of the pipeline cache.

To destroy a pipeline cache, call:

void vkDestroyPipelineCache(
    VkDevice                                    device,
    VkPipelineCache                             pipelineCache,
    const VkAllocationCallbacks*                pAllocator);

  • device is the logical device that destroys the pipeline cache object.

  • pipelineCache is the handle of the pipeline cache to destroy.

  • pAllocator controls host memory allocation as described in the Memory Allocation chapter.

Valid Usage

  • If VkAllocationCallbacks were provided when pipelineCache was created, a compatible set of callbacks must be provided here

  • If no VkAllocationCallbacks were provided when pipelineCache was created, pAllocator must be NULL

Valid Usage (Implicit)

  • device must be a valid VkDevice handle

  • If pipelineCache is not VK_NULL_HANDLE, pipelineCache must be a valid VkPipelineCache handle

  • If pAllocator is not NULL, pAllocator must be a valid pointer to a valid VkAllocationCallbacks structure

  • If pipelineCache is a valid handle, it must have been created, allocated, or retrieved from device

Host Synchronization

  • Host access to pipelineCache must be externally synchronized

9.7. Specialization Constants

Specialization constants are a mechanism whereby constants in a SPIR-V module can have their constant value specified at the time the VkPipeline is created. This allows a SPIR-V module to have constants that can be modified while executing an application that uses the Vulkan API.

Note

Specialization constants are useful to allow a compute shader to have its local workgroup size changed at runtime by the user, for example.

Each VkPipelineShaderStageCreateInfo structure contains a pSpecializationInfo member, which can be NULL to indicate no specialization constants, or point to a VkSpecializationInfo structure.

The VkSpecializationInfo structure is defined as:

typedef struct VkSpecializationInfo {
    uint32_t                           mapEntryCount;
    const VkSpecializationMapEntry*    pMapEntries;
    size_t                             dataSize;
    const void*                        pData;
} VkSpecializationInfo;

  • mapEntryCount is the number of entries in the pMapEntries array.

  • pMapEntries is a pointer to an array of VkSpecializationMapEntry structures which map constant IDs to offsets in pData.

  • dataSize is the byte size of the pData buffer.

  • pData contains the actual constant values to specialize with.

pMapEntries is a pointer to a VkSpecializationMapEntry structure.

Valid Usage

  • The offset member of each element of pMapEntries must be less than dataSize

  • The size member of each element of pMapEntries must be less than or equal to dataSize minus offset

Valid Usage (Implicit)

  • If mapEntryCount is not 0, pMapEntries must be a valid pointer to an array of mapEntryCount valid VkSpecializationMapEntry structures

  • If dataSize is not 0, pData must be a valid pointer to an array of dataSize bytes

The VkSpecializationMapEntry structure is defined as:

typedef struct VkSpecializationMapEntry {
    uint32_t    constantID;
    uint32_t    offset;
    size_t      size;
} VkSpecializationMapEntry;

  • constantID is the ID of the specialization constant in SPIR-V.

  • offset is the byte offset of the specialization constant value within the supplied data buffer.

  • size is the byte size of the specialization constant value within the supplied data buffer.

If a constantID value is not a specialization constant ID used in the shader, that map entry does not affect the behavior of the pipeline.

Valid Usage

  • For a constantID specialization constant declared in a shader, size must match the byte size of the constantID. If the specialization constant is of type boolean, size must be the byte size of VkBool32

In human readable SPIR-V:

OpDecorate %x SpecId 13 ; decorate .x component of WorkgroupSize with ID 13
OpDecorate %y SpecId 42 ; decorate .y component of WorkgroupSize with ID 42
OpDecorate %z SpecId 3  ; decorate .z component of WorkgroupSize with ID 3
OpDecorate %wgsize BuiltIn WorkgroupSize ; decorate WorkgroupSize onto constant
%i32 = OpTypeInt 32 0 ; declare an unsigned 32-bit type
%uvec3 = OpTypeVector %i32 3 ; declare a 3 element vector type of unsigned 32-bit
%x = OpSpecConstant %i32 1 ; declare the .x component of WorkgroupSize
%y = OpSpecConstant %i32 1 ; declare the .y component of WorkgroupSize
%z = OpSpecConstant %i32 1 ; declare the .z component of WorkgroupSize
%wgsize = OpSpecConstantComposite %uvec3 %x %y %z ; declare WorkgroupSize

From the above we have three specialization constants, one for each of the x, y & z elements of the WorkgroupSize vector.

Now to specialize the above via the specialization constants mechanism:

const VkSpecializationMapEntry entries[] =
{
    {
        13,                             // constantID
        0 * sizeof(uint32_t),           // offset
        sizeof(uint32_t)                // size
    },
    {
        42,                             // constantID
        1 * sizeof(uint32_t),           // offset
        sizeof(uint32_t)                // size
    },
    {
        3,                              // constantID
        2 * sizeof(uint32_t),           // offset
        sizeof(uint32_t)                // size
    }
};

const uint32_t data[] = { 16, 8, 4 }; // our workgroup size is 16x8x4

const VkSpecializationInfo info =
{
    3,                                  // mapEntryCount
    entries,                            // pMapEntries
    3 * sizeof(uint32_t),               // dataSize
    data,                               // pData
};

Then when calling vkCreateComputePipelines, and passing the VkSpecializationInfo we defined as the pSpecializationInfo parameter of VkPipelineShaderStageCreateInfo, we will create a compute pipeline with the runtime specified local workgroup size.

Another example would be that an application has a SPIR-V module that has some platform-dependent constants they wish to use.

In human readable SPIR-V:

OpDecorate %1 SpecId 0  ; decorate our signed 32-bit integer constant
OpDecorate %2 SpecId 12 ; decorate our 32-bit floating-point constant
%i32 = OpTypeInt 32 1   ; declare a signed 32-bit type
%float = OpTypeFloat 32 ; declare a 32-bit floating-point type
%1 = OpSpecConstant %i32 -1 ; some signed 32-bit integer constant
%2 = OpSpecConstant %float 0.5 ; some 32-bit floating-point constant

From the above we have two specialization constants, one is a signed 32-bit integer and the second is a 32-bit floating-point.

Now to specialize the above via the specialization constants mechanism:

struct SpecializationData {
    int32_t data0;
    float data1;
};

const VkSpecializationMapEntry entries[] =
{
    {
        0,                                    // constantID
        offsetof(SpecializationData, data0),  // offset
        sizeof(SpecializationData::data0)     // size
    },
    {
        12,                                   // constantID
        offsetof(SpecializationData, data1),  // offset
        sizeof(SpecializationData::data1)     // size
    }
};

SpecializationData data;
data.data0 = -42;    // set the data for the 32-bit integer
data.data1 = 42.0f;  // set the data for the 32-bit floating-point

const VkSpecializationInfo info =
{
    2,                                  // mapEntryCount
    entries,                            // pMapEntries
    sizeof(data),                       // dataSize
    &data,                              // pData
};

It is legal for a SPIR-V module with specializations to be compiled into a pipeline where no specialization info was provided. SPIR-V specialization constants contain default values such that if a specialization is not provided, the default value will be used. In the examples above, it would be valid for an application to only specialize some of the specialization constants within the SPIR-V module, and let the other constants use their default values encoded within the OpSpecConstant declarations.

9.8. Pipeline Binding

Once a pipeline has been created, it can be bound to the command buffer using the command:

void vkCmdBindPipeline(
    VkCommandBuffer                             commandBuffer,
    VkPipelineBindPoint                         pipelineBindPoint,
    VkPipeline                                  pipeline);

  • commandBuffer is the command buffer that the pipeline will be bound to.

  • pipelineBindPoint is a VkPipelineBindPoint value specifying whether to bind to the compute or graphics bind point. Binding one does not disturb the other.

  • pipeline is the pipeline to be bound.

Once bound, a pipeline binding affects subsequent graphics or compute commands in the command buffer until a different pipeline is bound to the bind point. The pipeline bound to VK_PIPELINE_BIND_POINT_COMPUTE controls the behavior of vkCmdDispatch and vkCmdDispatchIndirect. The pipeline bound to VK_PIPELINE_BIND_POINT_GRAPHICS controls the behavior of all drawing commands. No other commands are affected by the pipeline state.

Valid Usage

  • If pipelineBindPoint is VK_PIPELINE_BIND_POINT_COMPUTE, the VkCommandPool that commandBuffer was allocated from must support compute operations

  • If pipelineBindPoint is VK_PIPELINE_BIND_POINT_GRAPHICS, the VkCommandPool that commandBuffer was allocated from must support graphics operations

  • If pipelineBindPoint is VK_PIPELINE_BIND_POINT_COMPUTE, pipeline must be a compute pipeline

  • If pipelineBindPoint is VK_PIPELINE_BIND_POINT_GRAPHICS, pipeline must be a graphics pipeline

  • If the variable multisample rate feature is not supported, pipeline is a graphics pipeline, the current subpass has no attachments, and this is not the first call to this function with a graphics pipeline after transitioning to the current subpass, then the sample count specified by this pipeline must match that set in the previous pipeline

Valid Usage (Implicit)

  • commandBuffer must be a valid VkCommandBuffer handle

  • pipelineBindPoint must be a valid VkPipelineBindPoint value

  • pipeline must be a valid VkPipeline handle

  • commandBuffer must be in the recording state

  • The VkCommandPool that commandBuffer was allocated from must support graphics, or compute operations

  • Both of commandBuffer, and pipeline must have been created, allocated, or retrieved from the same VkDevice

Host Synchronization

  • Host access to commandBuffer must be externally synchronized

  • Host access to the VkCommandPool that commandBuffer was allocated from must be externally synchronized

Command Properties
Command Buffer Levels Render Pass Scope Supported Queue Types Pipeline Type

Primary
Secondary

Both

Graphics
Compute

Possible values of vkCmdBindPipeline::pipelineBindPoint, specifying the bind point of a pipeline object, are:

typedef enum VkPipelineBindPoint {
    VK_PIPELINE_BIND_POINT_GRAPHICS = 0,
    VK_PIPELINE_BIND_POINT_COMPUTE = 1,
    VK_PIPELINE_BIND_POINT_MAX_ENUM = 0x7FFFFFFF
} VkPipelineBindPoint;

  • VK_PIPELINE_BIND_POINT_COMPUTE specifies binding as a compute pipeline.

  • VK_PIPELINE_BIND_POINT_GRAPHICS specifies binding as a graphics pipeline.

9.9. Dynamic State

When a pipeline object is bound, any pipeline object state that is not specified as dynamic is applied to the command buffer state. Pipeline object state that is specified as dynamic is not applied to the command buffer state at this time. Instead, dynamic state can be modified at any time and persists for the lifetime of the command buffer, or until modified by another dynamic state setting command or another pipeline bind.

When a pipeline object is bound, the following applies to each state parameter:

  • If the state is not specified as dynamic in the new pipeline object, then that command buffer state is overwritten by the state in the new pipeline object. Before any draw or dispatch call with this pipeline there must not have been any call to any of the corresponding dynamic state setting commands after this pipeline was bound

  • If the state is specified as dynamic in the new pipeline object, then that command buffer state is not disturbed. Before any draw or dispatch call with this pipeline there must have been at least one call to each of the corresponding dynamic state setting commands since the command buffer recording was begun, or the last bound pipeline object with that state specified as static, whichever was the latter

Dynamic state that does not affect the result of operations can be left undefined.

Note

For example, if blending is disabled by the pipeline object state then the dynamic color blend constants do not need to be specified in the command buffer, even if this state is specified as dynamic in the pipeline object.