# VkSubpassDescription(3) Manual Page

## Name

VkSubpassDescription - Structure specifying a subpass description

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## C Specification

The `VkSubpassDescription` structure is defined as:

    // Provided by VK_VERSION_1_0
    typedef struct VkSubpassDescription {
        VkSubpassDescriptionFlags       flags;
        VkPipelineBindPoint             pipelineBindPoint;
        uint32_t                        inputAttachmentCount;
        const VkAttachmentReference*    pInputAttachments;
        uint32_t                        colorAttachmentCount;
        const VkAttachmentReference*    pColorAttachments;
        const VkAttachmentReference*    pResolveAttachments;
        const VkAttachmentReference*    pDepthStencilAttachment;
        uint32_t                        preserveAttachmentCount;
        const uint32_t*                 pPreserveAttachments;
    } VkSubpassDescription;

## Members

- `flags` is a bitmask of VkSubpassDescriptionFlagBits specifying usage of the subpass.

- `pipelineBindPoint` is a VkPipelineBindPoint value specifying the pipeline type supported for this subpass.

- `inputAttachmentCount` is the number of input attachments.

- `pInputAttachments` is a pointer to an array of VkAttachmentReference structures defining the input attachments for this subpass and their layouts.

- `colorAttachmentCount` is the number of color attachments.

- `pColorAttachments` is a pointer to an array of `colorAttachmentCount` VkAttachmentReference structures defining the color attachments for this subpass and their layouts.

- `pResolveAttachments` is `NULL` or a pointer to an array of `colorAttachmentCount` VkAttachmentReference structures defining the resolve attachments for this subpass and their layouts.

- `pDepthStencilAttachment` is a pointer to a VkAttachmentReference structure specifying the depth/stencil attachment for this subpass and its layout.

- `preserveAttachmentCount` is the number of preserved attachments.

- `pPreserveAttachments` is a pointer to an array of `preserveAttachmentCount` render pass attachment indices identifying attachments that are not used by this subpass, but whose contents must be preserved throughout the subpass.

## Description

Each element of the `pInputAttachments` array corresponds to an input attachment index in a fragment shader, i.e. if a shader declares an image variable decorated with a `InputAttachmentIndex` value of X, then it uses the attachment provided in `pInputAttachments`[X]. Input attachments must also be bound to the pipeline in a descriptor set. If the `attachment` member of any element of `pInputAttachments` is `VK_ATTACHMENT_UNUSED`, the application must not read from the corresponding input attachment index. Fragment shaders can use subpass input variables to access the contents of an input attachment at the fragment’s (xf,yf) framebuffer coordinates and layer. Input attachments must not be used by any subpasses within a render pass that enables render pass transform.

Each element of the `pColorAttachments` array corresponds to an output location in the shader, i.e. if the shader declares an output variable decorated with a `Location` value of X, then it uses the attachment provided in `pColorAttachments`[X]. If the `attachment` member of any element of `pColorAttachments` is `VK_ATTACHMENT_UNUSED`, or if Color Write Enable has been disabled for the corresponding attachment index, then writes to the corresponding location by a fragment shader are discarded.

If `flags` does not include `VK_SUBPASS_DESCRIPTION_SHADER_RESOLVE_BIT_QCOM`, and if `pResolveAttachments` is not `NULL`, each of its elements corresponds to a color attachment (the element in `pColorAttachments` at the same index), and a multisample resolve operation is defined for each attachment unless the resolve attachment index is `VK_ATTACHMENT_UNUSED`.

Similarly, if `flags` does not include `VK_SUBPASS_DESCRIPTION_SHADER_RESOLVE_BIT_QCOM`, and VkSubpassDescriptionDepthStencilResolve::`pDepthStencilResolveAttachment` is not `NULL` and does not have the value `VK_ATTACHMENT_UNUSED`, it corresponds to the depth/stencil attachment in `pDepthStencilAttachment`, and multisample resolve operation for depth and stencil are defined by VkSubpassDescriptionDepthStencilResolve::`depthResolveMode` and VkSubpassDescriptionDepthStencilResolve::`stencilResolveMode`, respectively. If VkSubpassDescriptionDepthStencilResolve::`depthResolveMode` is `VK_RESOLVE_MODE_NONE` or the `pDepthStencilResolveAttachment` does not have a depth aspect, no resolve operation is performed for the depth attachment. If VkSubpassDescriptionDepthStencilResolve::`stencilResolveMode` is `VK_RESOLVE_MODE_NONE` or the `pDepthStencilResolveAttachment` does not have a stencil aspect, no resolve operation is performed for the stencil attachment.

If the image subresource range referenced by the depth/stencil attachment is created with `VK_IMAGE_CREATE_SAMPLE_LOCATIONS_COMPATIBLE_DEPTH_BIT_EXT`, then the multisample resolve operation uses the sample locations state specified in the `sampleLocationsInfo` member of the element of the `VkRenderPassSampleLocationsBeginInfoEXT`::`pPostSubpassSampleLocations` for the subpass.

If `pDepthStencilAttachment` is `NULL`, or if its attachment index is `VK_ATTACHMENT_UNUSED`, it indicates that no depth/stencil attachment will be used in the subpass.

The contents of an attachment within the render area become undefined at the start of a subpass S if all of the following conditions are true:

- The attachment is used as a color, depth/stencil, or resolve attachment in any subpass in the render pass.

- There is a subpass S1 that uses or preserves the attachment, and a subpass dependency from S1 to S.

- The attachment is not used or preserved in subpass S.

In addition, the contents of an attachment within the render area become undefined at the start of a subpass S if all of the following conditions are true:

- `VK_SUBPASS_DESCRIPTION_SHADER_RESOLVE_BIT_QCOM` is set.

- The attachment is used as a color or depth/stencil in the subpass.

Once the contents of an attachment become undefined in subpass S, they remain undefined for subpasses in subpass dependency chains starting with subpass S until they are written again. However, they remain valid for subpasses in other subpass dependency chains starting with subpass S1 if those subpasses use or preserve the attachment.

Valid Usage

- VUID-VkSubpassDescription-attachment-06912
  If the `attachment` member of an element of `pInputAttachments` is not `VK_ATTACHMENT_UNUSED`, its `layout` member must not be `VK_IMAGE_LAYOUT_COLOR_ATTACHMENT_OPTIMAL` or `VK_IMAGE_LAYOUT_DEPTH_STENCIL_ATTACHMENT_OPTIMAL`

- VUID-VkSubpassDescription-attachment-06913
  If the `attachment` member of an element of `pColorAttachments` is not `VK_ATTACHMENT_UNUSED`, its `layout` member must not be `VK_IMAGE_LAYOUT_DEPTH_STENCIL_ATTACHMENT_OPTIMAL` or `VK_IMAGE_LAYOUT_SHADER_READ_ONLY_OPTIMAL`

- VUID-VkSubpassDescription-attachment-06914
  If the `attachment` member of an element of `pResolveAttachments` is not `VK_ATTACHMENT_UNUSED`, its `layout` member must not be `VK_IMAGE_LAYOUT_DEPTH_STENCIL_ATTACHMENT_OPTIMAL` or `VK_IMAGE_LAYOUT_SHADER_READ_ONLY_OPTIMAL`

- VUID-VkSubpassDescription-attachment-06915
  If the `attachment` member of `pDepthStencilAttachment` is not `VK_ATTACHMENT_UNUSED`, ts `layout` member must not be `VK_IMAGE_LAYOUT_COLOR_ATTACHMENT_OPTIMAL` or `VK_IMAGE_LAYOUT_SHADER_READ_ONLY_OPTIMAL`

- VUID-VkSubpassDescription-attachment-06916
  If the `attachment` member of an element of `pColorAttachments` is not `VK_ATTACHMENT_UNUSED`, its `layout` member must not be `VK_IMAGE_LAYOUT_DEPTH_ATTACHMENT_STENCIL_READ_ONLY_OPTIMAL` or `VK_IMAGE_LAYOUT_DEPTH_READ_ONLY_STENCIL_ATTACHMENT_OPTIMAL`

- VUID-VkSubpassDescription-attachment-06917
  If the `attachment` member of an element of `pResolveAttachments` is not `VK_ATTACHMENT_UNUSED`, its `layout` member must not be `VK_IMAGE_LAYOUT_DEPTH_ATTACHMENT_STENCIL_READ_ONLY_OPTIMAL` or `VK_IMAGE_LAYOUT_DEPTH_READ_ONLY_STENCIL_ATTACHMENT_OPTIMAL`

- VUID-VkSubpassDescription-attachment-06918
  If the `attachment` member of an element of `pInputAttachments` is not `VK_ATTACHMENT_UNUSED`, its `layout` member must not be `VK_IMAGE_LAYOUT_DEPTH_ATTACHMENT_OPTIMAL` or `VK_IMAGE_LAYOUT_STENCIL_ATTACHMENT_OPTIMAL`

- VUID-VkSubpassDescription-attachment-06919
  If the `attachment` member of an element of `pColorAttachments` is not `VK_ATTACHMENT_UNUSED`, its `layout` member must not be `VK_IMAGE_LAYOUT_DEPTH_ATTACHMENT_OPTIMAL`, `VK_IMAGE_LAYOUT_DEPTH_READ_ONLY_OPTIMAL`, `VK_IMAGE_LAYOUT_STENCIL_ATTACHMENT_OPTIMAL`, or `VK_IMAGE_LAYOUT_STENCIL_READ_ONLY_OPTIMAL`

- VUID-VkSubpassDescription-attachment-06920
  If the `attachment` member of an element of `pResolveAttachments` is not `VK_ATTACHMENT_UNUSED`, its `layout` member must not be `VK_IMAGE_LAYOUT_DEPTH_ATTACHMENT_OPTIMAL`, `VK_IMAGE_LAYOUT_DEPTH_READ_ONLY_OPTIMAL`, `VK_IMAGE_LAYOUT_STENCIL_ATTACHMENT_OPTIMAL`, or `VK_IMAGE_LAYOUT_STENCIL_READ_ONLY_OPTIMAL`

- VUID-VkSubpassDescription-attachment-06921
  If the `attachment` member of an element of `pInputAttachments` is not `VK_ATTACHMENT_UNUSED`, its `layout` member must not be `VK_IMAGE_LAYOUT_ATTACHMENT_OPTIMAL_KHR`

- VUID-VkSubpassDescription-attachment-06922
  If the `attachment` member of an element of `pColorAttachments` is not `VK_ATTACHMENT_UNUSED`, its `layout` member must not be `VK_IMAGE_LAYOUT_READ_ONLY_OPTIMAL_KHR`

- VUID-VkSubpassDescription-attachment-06923
  If the `attachment` member of an element of `pResolveAttachments` is not `VK_ATTACHMENT_UNUSED`, its `layout` member must not be `VK_IMAGE_LAYOUT_READ_ONLY_OPTIMAL_KHR`

- VUID-VkSubpassDescription-pipelineBindPoint-04952
  `pipelineBindPoint` must be `VK_PIPELINE_BIND_POINT_GRAPHICS` or `VK_PIPELINE_BIND_POINT_SUBPASS_SHADING_HUAWEI`

- VUID-VkSubpassDescription-colorAttachmentCount-00845
  `colorAttachmentCount` must be less than or equal to `VkPhysicalDeviceLimits`::`maxColorAttachments`

- VUID-VkSubpassDescription-loadOp-00846
  If the first use of an attachment in this render pass is as an input attachment, and the attachment is not also used as a color or depth/stencil attachment in the same subpass, then `loadOp` must not be `VK_ATTACHMENT_LOAD_OP_CLEAR`

- VUID-VkSubpassDescription-pResolveAttachments-00847
  If `pResolveAttachments` is not `NULL`, for each resolve attachment that is not `VK_ATTACHMENT_UNUSED`, the corresponding color attachment must not be `VK_ATTACHMENT_UNUSED`

- VUID-VkSubpassDescription-pResolveAttachments-00848
  If `pResolveAttachments` is not `NULL`, for each resolve attachment that is not `VK_ATTACHMENT_UNUSED`, the corresponding color attachment must not have a sample count of `VK_SAMPLE_COUNT_1_BIT`

- VUID-VkSubpassDescription-pResolveAttachments-00849
  If `pResolveAttachments` is not `NULL`, each resolve attachment that is not `VK_ATTACHMENT_UNUSED` must have a sample count of `VK_SAMPLE_COUNT_1_BIT`

- VUID-VkSubpassDescription-pResolveAttachments-00850
  If `pResolveAttachments` is not `NULL`, each resolve attachment that is not `VK_ATTACHMENT_UNUSED` must have the same VkFormat as its corresponding color attachment

- VUID-VkSubpassDescription-pColorAttachments-09430
  All attachments in `pColorAttachments` that are not `VK_ATTACHMENT_UNUSED` must have the same sample count

- VUID-VkSubpassDescription-pInputAttachments-02647
  All attachments in `pInputAttachments` that are not `VK_ATTACHMENT_UNUSED` must have image formats whose potential format features contain at least `VK_FORMAT_FEATURE_COLOR_ATTACHMENT_BIT` or `VK_FORMAT_FEATURE_DEPTH_STENCIL_ATTACHMENT_BIT`

- VUID-VkSubpassDescription-pColorAttachments-02648
  All attachments in `pColorAttachments` that are not `VK_ATTACHMENT_UNUSED` must have image formats whose potential format features contain `VK_FORMAT_FEATURE_COLOR_ATTACHMENT_BIT`

- VUID-VkSubpassDescription-pResolveAttachments-02649
  All attachments in `pResolveAttachments` that are not `VK_ATTACHMENT_UNUSED` must have image formats whose potential format features contain `VK_FORMAT_FEATURE_COLOR_ATTACHMENT_BIT`

- VUID-VkSubpassDescription-pDepthStencilAttachment-02650
  If `pDepthStencilAttachment` is not `NULL` and the attachment is not `VK_ATTACHMENT_UNUSED` then it must have an image format whose potential format features contain `VK_FORMAT_FEATURE_DEPTH_STENCIL_ATTACHMENT_BIT`

- VUID-VkSubpassDescription-linearColorAttachment-06496
  If the `linearColorAttachment` feature is enabled and the image is created with `VK_IMAGE_TILING_LINEAR`, all attachments in `pInputAttachments` that are not `VK_ATTACHMENT_UNUSED` must have image formats whose potential format features must contain `VK_FORMAT_FEATURE_2_LINEAR_COLOR_ATTACHMENT_BIT_NV`

- VUID-VkSubpassDescription-linearColorAttachment-06497
  If the `linearColorAttachment` feature is enabled and the image is created with `VK_IMAGE_TILING_LINEAR`, all attachments in `pColorAttachments` that are not `VK_ATTACHMENT_UNUSED` must have image formats whose potential format features must contain `VK_FORMAT_FEATURE_2_LINEAR_COLOR_ATTACHMENT_BIT_NV`

- VUID-VkSubpassDescription-linearColorAttachment-06498
  If the `linearColorAttachment` feature is enabled and the image is created with `VK_IMAGE_TILING_LINEAR`, all attachments in `pResolveAttachments` that are not `VK_ATTACHMENT_UNUSED` must have image formats whose potential format features must contain `VK_FORMAT_FEATURE_2_LINEAR_COLOR_ATTACHMENT_BIT_NV`

- VUID-VkSubpassDescription-None-09431
  If either of the following is enabled:

  - The `VK_AMD_mixed_attachment_samples` extension

  - The `VK_NV_framebuffer_mixed_samples` extension

  all attachments in `pColorAttachments` that are not `VK_ATTACHMENT_UNUSED` must have a sample count that is smaller than or equal to the sample count of `pDepthStencilAttachment` if it is not `VK_ATTACHMENT_UNUSED`

- VUID-VkSubpassDescription-pDepthStencilAttachment-01418
  If `pDepthStencilAttachment` is not `VK_ATTACHMENT_UNUSED` and any attachments in `pColorAttachments` are not `VK_ATTACHMENT_UNUSED`, they must have the same sample count , if none of the following are enabled:

  - The `VK_AMD_mixed_attachment_samples` extension

  - The `VK_NV_framebuffer_mixed_samples` extension

- VUID-VkSubpassDescription-attachment-00853
  Each element of `pPreserveAttachments` must not be `VK_ATTACHMENT_UNUSED`

- VUID-VkSubpassDescription-pPreserveAttachments-00854
  Each element of `pPreserveAttachments` must not also be an element of any other member of the subpass description

- VUID-VkSubpassDescription-layout-02519
  If any attachment is used by more than one VkAttachmentReference member, then each use must use the same `layout`

- VUID-VkSubpassDescription-flags-00856
  If `flags` includes `VK_SUBPASS_DESCRIPTION_PER_VIEW_POSITION_X_ONLY_BIT_NVX`, it must also include `VK_SUBPASS_DESCRIPTION_PER_VIEW_ATTRIBUTES_BIT_NVX`

- VUID-VkSubpassDescription-flags-03341
  If `flags` includes `VK_SUBPASS_DESCRIPTION_SHADER_RESOLVE_BIT_QCOM`, and if `pResolveAttachments` is not `NULL`, then each resolve attachment must be `VK_ATTACHMENT_UNUSED`

- VUID-VkSubpassDescription-flags-03343
  If `flags` includes `VK_SUBPASS_DESCRIPTION_SHADER_RESOLVE_BIT_QCOM`, then the subpass must be the last subpass in a subpass dependency chain

- VUID-VkSubpassDescription-pInputAttachments-02868
  If the render pass is created with `VK_RENDER_PASS_CREATE_TRANSFORM_BIT_QCOM` each of the elements of `pInputAttachments` must be `VK_ATTACHMENT_UNUSED`

- VUID-VkSubpassDescription-pDepthStencilAttachment-04438
  `pDepthStencilAttachment` and `pColorAttachments` must not contain references to the same attachment

Valid Usage (Implicit)

- VUID-VkSubpassDescription-flags-parameter
  `flags` must be a valid combination of VkSubpassDescriptionFlagBits values

- VUID-VkSubpassDescription-pipelineBindPoint-parameter
  `pipelineBindPoint` must be a valid VkPipelineBindPoint value

- VUID-VkSubpassDescription-pInputAttachments-parameter
  If `inputAttachmentCount` is not `0`, `pInputAttachments` must be a valid pointer to an array of `inputAttachmentCount` valid VkAttachmentReference structures

- VUID-VkSubpassDescription-pColorAttachments-parameter
  If `colorAttachmentCount` is not `0`, `pColorAttachments` must be a valid pointer to an array of `colorAttachmentCount` valid VkAttachmentReference structures

- VUID-VkSubpassDescription-pResolveAttachments-parameter
  If `colorAttachmentCount` is not `0`, and `pResolveAttachments` is not `NULL`, `pResolveAttachments` must be a valid pointer to an array of `colorAttachmentCount` valid VkAttachmentReference structures

- VUID-VkSubpassDescription-pDepthStencilAttachment-parameter
  If `pDepthStencilAttachment` is not `NULL`, `pDepthStencilAttachment` must be a valid pointer to a valid VkAttachmentReference structure

- VUID-VkSubpassDescription-pPreserveAttachments-parameter
  If `preserveAttachmentCount` is not `0`, `pPreserveAttachments` must be a valid pointer to an array of `preserveAttachmentCount` `uint32_t` values

## See Also

VK_VERSION_1_0, VkAttachmentReference, VkPipelineBindPoint, VkRenderPassCreateInfo, VkSubpassDescriptionFlags

## Document Notes

For more information, see the Vulkan Specification

This page is extracted from the Vulkan Specification. Fixes and changes should be made to the Specification, not directly.

## Copyright

Copyright 2014-2024 The Khronos Group Inc.

SPDX-License-Identifier: CC-BY-4.0