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
-
flagsis a bitmask of VkSubpassDescriptionFlagBits specifying usage of the subpass. -
pipelineBindPointis a VkPipelineBindPoint value specifying the pipeline type supported for this subpass. -
inputAttachmentCountis the number of input attachments. -
pInputAttachmentsis a pointer to an array of VkAttachmentReference structures defining the input attachments for this subpass and their layouts. -
colorAttachmentCountis the number of color attachments. -
pColorAttachmentsis a pointer to an array of VkAttachmentReference structures defining the color attachments for this subpass and their layouts. -
pResolveAttachmentsis an optional array ofcolorAttachmentCountVkAttachmentReference structures defining the resolve attachments for this subpass and their layouts. -
pDepthStencilAttachmentis a pointer to a VkAttachmentReference structure specifying the depth/stencil attachment for this subpass and its layout. -
preserveAttachmentCountis the number of preserved attachments. -
pPreserveAttachmentsis a pointer to an array ofpreserveAttachmentCountrender 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 (x, y, layer) framebuffer coordinates.
Input attachments must not be used by any subpasses within a renderpass
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 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.
At the end of each subpass, multisample resolve operations read the
subpass’s color attachments, and resolve the samples for each pixel within
the render area to the same pixel location in the corresponding resolve
attachments, 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 operations for depth
and stencil are defined by
VkSubpassDescriptionDepthStencilResolve::depthResolveMode and
VkSubpassDescriptionDepthStencilResolve::stencilResolveMode,
respectively.
At the end of each subpass, multisample resolve operations read the
subpass’s depth/stencil attachment, and resolve the samples for each pixel
to the same pixel location in the corresponding resolve attachment.
If VkSubpassDescriptionDepthStencilResolve::depthResolveMode is
VK_RESOLVE_MODE_NONE, then the depth component of the resolve
attachment is not written to and its contents are preserved.
Similarly, if
VkSubpassDescriptionDepthStencilResolve::stencilResolveMode is
VK_RESOLVE_MODE_NONE, then the stencil component of the resolve
attachment is not written to and its contents are preserved.
VkSubpassDescriptionDepthStencilResolve::depthResolveMode is
ignored if the VkFormat of the pDepthStencilResolveAttachment
does not have a depth component.
Similarly,
VkSubpassDescriptionDepthStencilResolve::stencilResolveMode is
ignored if the VkFormat of the pDepthStencilResolveAttachment
does not have a stencil component.
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_QCOMis 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.
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.