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VK_HUAWEI_subpass_shading

Other Extension Metadata

Last Modified Date

2021-06-01

Interactions and External Dependencies
Contributors
  • Hueilong Wang
  • Juntao Li, Huawei
  • Renmiao Lu, Huawei
  • Pan Gao, Huawei

Description

This extension allows applications to execute a subpass shading pipeline in a subpass of a render pass in order to save memory bandwidth for algorithms like tile-based deferred rendering and forward plus. A subpass shading pipeline is a pipeline with the compute pipeline ability, allowed to read values from input attachments, and only allowed to be dispatched inside a stand-alone subpass. Its work dimension is defined by the render pass’s render area size. Its workgroup size (width, height) shall be a power-of-two number in width or height, with minimum value from 8, and maximum value shall be decided from the render pass attachments and sample counts but depends on implementation.

The GlobalInvocationId.xy of a subpass shading pipeline is equal to the FragCoord.xy of a graphic pipeline in the same render pass subtracted the offset of the VkRenderPassBeginInfo::renderArea. GlobalInvocationId.z is mapped to the Layer if VK_EXT_shader_viewport_index_layer is supported. The GlobalInvocationId.xy is equal to the index of the local workgroup multiplied by the size of the local workgroup plus the LocalInvocationId and the offset of the VkRenderPassBeginInfo::renderArea.

This extension allows a subpass’s pipeline bind point to be VK_PIPELINE_BIND_POINT_SUBPASS_SHADING_HUAWEI.

New Commands

New Structures

New Enum Constants

  • VK_HUAWEI_SUBPASS_SHADING_EXTENSION_NAME
  • VK_HUAWEI_SUBPASS_SHADING_SPEC_VERSION
  • Extending VkPipelineBindPoint:
    • VK_PIPELINE_BIND_POINT_SUBPASS_SHADING_HUAWEI
  • Extending VkPipelineStageFlagBits2:
    • VK_PIPELINE_STAGE_2_SUBPASS_SHADER_BIT_HUAWEI
    • VK_PIPELINE_STAGE_2_SUBPASS_SHADING_BIT_HUAWEI
  • Extending VkShaderStageFlagBits:
    • VK_SHADER_STAGE_SUBPASS_SHADING_BIT_HUAWEI
  • Extending VkStructureType:
    • VK_STRUCTURE_TYPE_PHYSICAL_DEVICE_SUBPASS_SHADING_FEATURES_HUAWEI
    • VK_STRUCTURE_TYPE_PHYSICAL_DEVICE_SUBPASS_SHADING_PROPERTIES_HUAWEI
    • VK_STRUCTURE_TYPE_SUBPASS_SHADING_PIPELINE_CREATE_INFO_HUAWEI

Sample Code

Example of subpass shading in a GLSL shader

#extension GL_HUAWEI_subpass_shading: enable
#extension GL_KHR_shader_subgroup_arithmetic: enable

layout(constant_id = 0) const uint tileWidth = 8;
layout(constant_id = 1) const uint tileHeight = 8;
layout(local_size_x_id = 0, local_size_y_id = 1, local_size_z = 1) in;
layout(set=0, binding=0, input_attachment_index=0) uniform subpassInput depth;

void main()
{
  float d = subpassLoad(depth).x;
  float minD = subgroupMin(d);
  float maxD = subgroupMax(d);
}

Example of subpass shading dispatching in a subpass

vkCmdNextSubpass(commandBuffer, VK_SUBPASS_CONTENTS_INLINE);
vkCmdBindPipeline(commandBuffer, VK_PIPELINE_BIND_POINT_SUBPASS_SHADING_HUAWEI, subpassShadingPipeline);
vkCmdBindDescriptorSets(commandBuffer, VK_PIPELINE_BIND_POINT_SUBPASS_SHADING_HUAWEI, subpassShadingPipelineLayout,
  firstSet, descriptorSetCount, pDescriptorSets, dynamicOffsetCount, pDynamicOffsets);
vkCmdSubpassShadingHUAWEI(commandBuffer)
vkCmdEndRenderPass(commandBuffer);

Example of subpass shading render pass creation

VkAttachmentDescription2 attachments[] = {
  {
    VK_STRUCTURE_TYPE_ATTACHMENT_DESCRIPTION_2, NULL,
    0, VK_FORMAT_R8G8B8A8_UNORM, VK_SAMPLE_COUNT_1_BIT,
    VK_ATTACHMENT_LOAD_OP_CLEAR, VK_ATTACHMENT_STORE_OP_DONT_CARE,
    VK_ATTACHMENT_LOAD_OP_DONT_CARE, VK_ATTACHMENT_LOAD_OP_DONT_CARE,
    VK_IMAGE_LAYOUT_COLOR_ATTACHMENT_OPTIMAL, VK_IMAGE_LAYOUT_COLOR_ATTACHMENT_OPTIMAL
  },
  {
    VK_STRUCTURE_TYPE_ATTACHMENT_DESCRIPTION_2, NULL,
    0, VK_FORMAT_R8G8B8A8_UNORM, VK_SAMPLE_COUNT_1_BIT,
    VK_ATTACHMENT_LOAD_OP_CLEAR, VK_ATTACHMENT_STORE_OP_DONT_CARE,
    VK_ATTACHMENT_LOAD_OP_DONT_CARE, VK_ATTACHMENT_LOAD_OP_DONT_CARE,
    VK_IMAGE_LAYOUT_COLOR_ATTACHMENT_OPTIMAL, VK_IMAGE_LAYOUT_COLOR_ATTACHMENT_OPTIMAL
  },
  {
    VK_STRUCTURE_TYPE_ATTACHMENT_DESCRIPTION_2, NULL,
    0, VK_FORMAT_R8G8B8A8_UNORM, VK_SAMPLE_COUNT_1_BIT,
    VK_ATTACHMENT_LOAD_OP_CLEAR, VK_ATTACHMENT_STORE_OP_DONT_CARE,
    VK_ATTACHMENT_LOAD_OP_DONT_CARE, VK_ATTACHMENT_LOAD_OP_DONT_CARE,
    VK_IMAGE_LAYOUT_COLOR_ATTACHMENT_OPTIMAL, VK_IMAGE_LAYOUT_COLOR_ATTACHMENT_OPTIMAL
  },
  {
    VK_STRUCTURE_TYPE_ATTACHMENT_DESCRIPTION_2, NULL,
    0, VK_FORMAT_D24_UNORM_S8_UINT, VK_SAMPLE_COUNT_1_BIT,
    VK_ATTACHMENT_LOAD_OP_CLEAR, VK_ATTACHMENT_STORE_OP_DONT_CARE,
    VK_ATTACHMENT_LOAD_OP_CLEAR, VK_ATTACHMENT_LOAD_OP_DONT_CARE,
    VK_IMAGE_LAYOUT_DEPTH_STENCIL_ATTACHMENT_OPTIMAL, VK_IMAGE_LAYOUT_DEPTH_STENCIL_ATTACHMENT_OPTIMAL
  },
  {
    VK_STRUCTURE_TYPE_ATTACHMENT_DESCRIPTION_2, NULL,
    0, VK_FORMAT_R8G8B8A8_UNORM, VK_SAMPLE_COUNT_1_BIT,
    VK_ATTACHMENT_LOAD_OP_CLEAR, VK_ATTACHMENT_STORE_OP_STORE,
    VK_ATTACHMENT_LOAD_OP_DONT_CARE, VK_ATTACHMENT_LOAD_OP_DONT_CARE,
    VK_IMAGE_LAYOUT_COLOR_ATTACHMENT_OPTIMAL, VK_IMAGE_LAYOUT_COLOR_ATTACHMENT_OPTIMAL
  }
};

VkAttachmentReference2 gBufferAttachmentReferences[] = {
  { VK_STRUCTURE_TYPE_ATTACHMENT_REFERENCE_2, NULL, 0, VK_IMAGE_LAYOUT_COLOR_ATTACHMENT_OPTIMAL, VK_IMAGE_ASPECT_COLOR_BIT },
  { VK_STRUCTURE_TYPE_ATTACHMENT_REFERENCE_2, NULL, 1, VK_IMAGE_LAYOUT_COLOR_ATTACHMENT_OPTIMAL, VK_IMAGE_ASPECT_COLOR_BIT },
  { VK_STRUCTURE_TYPE_ATTACHMENT_REFERENCE_2, NULL, 2, VK_IMAGE_LAYOUT_COLOR_ATTACHMENT_OPTIMAL, VK_IMAGE_ASPECT_COLOR_BIT }
};
VkAttachmentReference2 gBufferDepthStencilAttachmentReferences =
  { VK_STRUCTURE_TYPE_ATTACHMENT_REFERENCE_2, NULL, 3, VK_IMAGE_LAYOUT_DEPTH_STENCIL_ATTACHMENT_OPTIMAL, VK_IMAGE_ASPECT_DEPTH_BIT|VK_IMAGE_ASPECT_STENCIL_BIT };
VkAttachmentReference2 depthInputAttachmentReferences[] = {
  { VK_STRUCTURE_TYPE_ATTACHMENT_REFERENCE_2, NULL, 3, VK_IMAGE_LAYOUT_DEPTH_STENCIL_READ_ONLY_OPTIMAL, VK_IMAGE_ASPECT_DEPTH_BIT|VK_IMAGE_ASPECT_STENCIL_BIT };
};
VkAttachmentReference2 preserveAttachmentReferences[] = {
  { VK_STRUCTURE_TYPE_ATTACHMENT_REFERENCE_2, NULL, 0, VK_IMAGE_LAYOUT_COLOR_ATTACHMENT_OPTIMAL, VK_IMAGE_ASPECT_COLOR_BIT },
  { VK_STRUCTURE_TYPE_ATTACHMENT_REFERENCE_2, NULL, 1, VK_IMAGE_LAYOUT_COLOR_ATTACHMENT_OPTIMAL, VK_IMAGE_ASPECT_COLOR_BIT },
  { VK_STRUCTURE_TYPE_ATTACHMENT_REFERENCE_2, NULL, 2, VK_IMAGE_LAYOUT_COLOR_ATTACHMENT_OPTIMAL, VK_IMAGE_ASPECT_COLOR_BIT },
  { VK_STRUCTURE_TYPE_ATTACHMENT_REFERENCE_2, NULL, 3, VK_IMAGE_LAYOUT_DEPTH_STENCIL_ATTACHMENT_OPTIMAL, VK_IMAGE_ASPECT_DEPTH_BIT|VK_IMAGE_ASPECT_STENCIL_BIT }
}; // G buffer including depth/stencil
VkAttachmentReference2 colorAttachmentReferences[] = {
  { VK_STRUCTURE_TYPE_ATTACHMENT_REFERENCE_2, NULL, 4, VK_IMAGE_LAYOUT_COLOR_ATTACHMENT_OPTIMAL, VK_IMAGE_ASPECT_COLOR_BIT }
};
VkAttachmentReference2 resolveAttachmentReference =
  { VK_STRUCTURE_TYPE_ATTACHMENT_REFERENCE_2, NULL, 4, VK_IMAGE_LAYOUT_COLOR_ATTACHMENT_OPTIMAL, VK_IMAGE_ASPECT_COLOR_BIT };

VkSubpassDescription2 subpasses[] = {
  {
    VK_STRUCTURE_TYPE_SUBPASS_DESCRIPTION_2, NULL, 0, VK_PIPELINE_BIND_POINT_GRAPHICS, 0,
    0, NULL, // input
    sizeof(gBufferAttachmentReferences)/sizeof(gBufferAttachmentReferences[0]), gBufferAttachmentReferences, // color
    NULL, &gBufferDepthStencilAttachmentReferences, // resolve & DS
    0, NULL
  },
  {
    VK_STRUCTURE_TYPE_SUBPASS_DESCRIPTION_2, NULL, 0, VK_PIPELINE_BIND_POINT_SUBPASS_SHADING_HUAWEI , 0,
    sizeof(depthInputAttachmentReferences)/sizeof(depthInputAttachmentReferences[0]), depthInputAttachmentReferences, // input
    0, NULL, // color
    NULL, NULL, // resolve & DS
    sizeof(preserveAttachmentReferences)/sizeof(preserveAttachmentReferences[0]), preserveAttachmentReferences,
  },
  {
    VK_STRUCTURE_TYPE_SUBPASS_DESCRIPTION_2, NULL, 0, VK_PIPELINE_BIND_POINT_GRAPHICS, 0,
    sizeof(gBufferAttachmentReferences)/sizeof(gBufferAttachmentReferences[0]), gBufferAttachmentReferences, // input
    sizeof(colorAttachmentReferences)/sizeof(colorAttachmentReferences[0]), colorAttachmentReferences, // color
    &resolveAttachmentReference, &gBufferDepthStencilAttachmentReferences, // resolve & DS
    0, NULL
  },
};

VkMemoryBarrier2KHR fragmentToSubpassShading = {
  VK_STRUCTURE_TYPE_MEMORY_BARRIER_2_KHR, NULL,
  VK_PIPELINE_STAGE_2_FRAGMENT_SHADER_BIT_KHR, VK_ACCESS_COLOR_ATTACHMENT_WRITE_BIT|VK_ACCESS_DEPTH_STENCIL_ATTACHMENT_WRITE_BIT,
  VK_PIPELINE_STAGE_2_SUBPASS_SHADER_BIT_HUAWEI, VK_ACCESS_INPUT_ATTACHMENT_READ_BIT
};

VkMemoryBarrier2KHR subpassShadingToFragment = {
  VK_STRUCTURE_TYPE_MEMORY_BARRIER_2_KHR, NULL,
  VK_PIPELINE_STAGE_2_SUBPASS_SHADER_BIT_HUAWEI, VK_ACCESS_SHADER_WRITE_BIT,
  VK_PIPELINE_STAGE_2_FRAGMENT_SHADER_BIT_KHR, VK_ACCESS_SHADER_READ_BIT
};

VkSubpassDependency2 dependencies[] = {
  {
    VK_STRUCTURE_TYPE_SUBPASS_DEPENDENCY_2, &fragmentToSubpassShading,
    0, 1,
    0, 0, 0, 0,
    0, 0
  },
  {
    VK_STRUCTURE_TYPE_SUBPASS_DEPENDENCY_2, &subpassShadingToFragment,
    1, 2,
    0, 0, 0, 0,
    0, 0
  },
};

VkRenderPassCreateInfo2 renderPassCreateInfo = {
  VK_STRUCTURE_TYPE_RENDER_PASS_CREATE_INFO_2, NULL, 0,
    sizeof(attachments)/sizeof(attachments[0]), attachments,
    sizeof(subpasses)/sizeof(subpasses[0]), subpasses,
    sizeof(dependencies)/sizeof(dependencies[0]), dependencies,
    0, NULL
};
VKRenderPass renderPass;
vkCreateRenderPass2(device, &renderPassCreateInfo, NULL, &renderPass);

Example of subpass shading pipeline creation

VkExtent2D maxWorkgroupSize;

VkSpecializationMapEntry subpassShadingConstantMapEntries[] = {
  { 0, 0 * sizeof(uint32_t), sizeof(uint32_t) },
  { 1, 1 * sizeof(uint32_t), sizeof(uint32_t) }
};

VkSpecializationInfo subpassShadingConstants = {
  2, subpassShadingConstantMapEntries,
  sizeof(VkExtent2D), &maxWorkgroupSize
};

VkSubpassShadingPipelineCreateInfoHUAWEI subpassShadingPipelineCreateInfo {
  VK_STRUCTURE_TYPE_SUBPASSS_SHADING_PIPELINE_CREATE_INFO_HUAWEI, NULL,
  renderPass, 1
};

VkPipelineShaderStageCreateInfo subpassShadingPipelineStageCreateInfo {
  VK_STRUCTURE_TYPE_PIPELINE_SHADER_STAGE_CREATE_INFO, NULL,
  0, VK_SHADER_STAGE_SUBPASS_SHADING_BIT_HUAWEI,
  shaderModule, "main",
  &subpassShadingConstants
};

VkComputePipelineCreateInfo subpassShadingComputePipelineCreateInfo = {
  VK_STRUCTURE_TYPE_COMPUTE_PIPELINE_CREATE_INFO, &subpassShadingPipelineCreateInfo,
  0, &subpassShadingPipelineStageCreateInfo,
  pipelineLayout, basePipelineHandle, basePipelineIndex
};

VKPipeline pipeline;

vkGetDeviceSubpassShadingMaxWorkgroupSizeHUAWEI(device, renderPass, &maxWorkgroupSize);
vkCreateComputePipelines(device, pipelineCache, 1, &subpassShadingComputePipelineCreateInfo, NULL, &pipeline);

Version History

  • Revision 3, 2023-06-19 (Pan Gao)
    • Rename VK_PIPELINE_STAGE_2_SUBPASS_SHADING_BIT_HUAWEI to VK_PIPELINE_STAGE_2_SUBPASS_SHADER_BIT_HUAWEI to better aligned with naming of other pipeline stages
  • Revision 2, 2021-06-28 (Hueilong Wang)
    • Change vkGetSubpassShadingMaxWorkgroupSizeHUAWEI to vkGetDeviceSubpassShadingMaxWorkgroupSizeHUAWEI to resolve issue pub1564
  • Revision 1, 2020-12-15 (Hueilong Wang)
    • Initial draft.