Render Pass
Draw commands must be recorded within a render pass instance. Each render pass instance defines a set of image resources, referred to as attachments, used during rendering.
To begin a render pass instance, call:
// Provided by VK_VERSION_1_3
void vkCmdBeginRendering(
VkCommandBuffer commandBuffer,
const VkRenderingInfo* pRenderingInfo);
or the equivalent command
// Provided by VK_KHR_dynamic_rendering
void vkCmdBeginRenderingKHR(
VkCommandBuffer commandBuffer,
const VkRenderingInfo* pRenderingInfo);
-
commandBuffer
is the command buffer in which to record the command. -
pRenderingInfo
is a pointer to a VkRenderingInfo structure specifying details of the render pass instance to begin.
After beginning a render pass instance, the command buffer is ready to record draw commands.
If pRenderingInfo->flags
includes VK_RENDERING_RESUMING_BIT
then
this render pass is resumed from a render pass instance that has been
suspended earlier in submission order.
The VkRenderingInfo
structure is defined as:
// Provided by VK_VERSION_1_3
typedef struct VkRenderingInfo {
VkStructureType sType;
const void* pNext;
VkRenderingFlags flags;
VkRect2D renderArea;
uint32_t layerCount;
uint32_t viewMask;
uint32_t colorAttachmentCount;
const VkRenderingAttachmentInfo* pColorAttachments;
const VkRenderingAttachmentInfo* pDepthAttachment;
const VkRenderingAttachmentInfo* pStencilAttachment;
} VkRenderingInfo;
or the equivalent
// Provided by VK_KHR_dynamic_rendering, VK_QCOM_tile_properties with VK_KHR_dynamic_rendering or VK_VERSION_1_3
typedef VkRenderingInfo VkRenderingInfoKHR;
-
sType
is a VkStructureType value identifying this structure. -
pNext
isNULL
or a pointer to a structure extending this structure. -
flags
is a bitmask of VkRenderingFlagBits. -
renderArea
is the render area that is affected by the render pass instance. -
layerCount
is the number of layers rendered to in each attachment whenviewMask
is0
. -
viewMask
is the view mask indicating the indices of attachment layers that will be rendered when it is not0
. -
colorAttachmentCount
is the number of elements inpColorAttachments
. -
pColorAttachments
is a pointer to an array ofcolorAttachmentCount
VkRenderingAttachmentInfo structures describing any color attachments used. -
pDepthAttachment
is a pointer to a VkRenderingAttachmentInfo structure describing a depth attachment. -
pStencilAttachment
is a pointer to a VkRenderingAttachmentInfo structure describing a stencil attachment.
If viewMask
is not 0
, multiview is enabled.
If there is an instance of VkDeviceGroupRenderPassBeginInfo included
in the pNext
chain and its deviceRenderAreaCount
member is not
0
, then renderArea
is ignored, and the render area is defined
per-device by that structure.
If multiview is enabled, and the multiviewPerViewRenderAreas
feature is enabled, and there is an
instance of VkMultiviewPerViewRenderAreasRenderPassBeginInfoQCOM
included in the pNext
chain with perViewRenderAreaCount
not
equal to 0
, then the elements of
VkMultiviewPerViewRenderAreasRenderPassBeginInfoQCOM::pPerViewRenderAreas
override renderArea
and define a render area for each view.
In this case, renderArea
must be set to an area at least as large as
the union of all the per-view render areas.
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 imageView
member of any element of pColorAttachments
is
VK_NULL_HANDLE,
and resolveMode
is not
VK_RESOLVE_MODE_EXTERNAL_FORMAT_DOWNSAMPLE_ANDROID
,
writes to the corresponding location by a fragment are discarded.
Bits which can be set in VkRenderingInfo::flags
describing
additional properties of the render pass are:
// Provided by VK_VERSION_1_3
typedef enum VkRenderingFlagBits {
VK_RENDERING_CONTENTS_SECONDARY_COMMAND_BUFFERS_BIT = 0x00000001,
VK_RENDERING_SUSPENDING_BIT = 0x00000002,
VK_RENDERING_RESUMING_BIT = 0x00000004,
// Provided by VK_EXT_legacy_dithering with (VK_KHR_dynamic_rendering or VK_VERSION_1_3) and VK_KHR_maintenance5
VK_RENDERING_ENABLE_LEGACY_DITHERING_BIT_EXT = 0x00000008,
// Provided by VK_KHR_maintenance7
VK_RENDERING_CONTENTS_INLINE_BIT_KHR = 0x00000010,
VK_RENDERING_CONTENTS_SECONDARY_COMMAND_BUFFERS_BIT_KHR = VK_RENDERING_CONTENTS_SECONDARY_COMMAND_BUFFERS_BIT,
VK_RENDERING_SUSPENDING_BIT_KHR = VK_RENDERING_SUSPENDING_BIT,
VK_RENDERING_RESUMING_BIT_KHR = VK_RENDERING_RESUMING_BIT,
// Provided by VK_EXT_nested_command_buffer
VK_RENDERING_CONTENTS_INLINE_BIT_EXT = VK_RENDERING_CONTENTS_INLINE_BIT_KHR,
} VkRenderingFlagBits;
or the equivalent
// Provided by VK_KHR_dynamic_rendering
typedef VkRenderingFlagBits VkRenderingFlagBitsKHR;
-
VK_RENDERING_CONTENTS_SECONDARY_COMMAND_BUFFERS_BIT
specifies that draw calls for the render pass instance will be recorded in secondary command buffers. If thenestedCommandBuffer
feature is enabled, the draw calls can come from both inline and vkCmdExecuteCommands. -
VK_RENDERING_RESUMING_BIT
specifies that the render pass instance is resuming an earlier suspended render pass instance. -
VK_RENDERING_SUSPENDING_BIT
specifies that the render pass instance will be suspended. -
VK_RENDERING_ENABLE_LEGACY_DITHERING_BIT_EXT
specifies that Legacy Dithering is enabled for the render pass instance. -
VK_RENDERING_CONTENTS_INLINE_BIT_KHR
specifies that draw calls for the render pass instance can be recorded inline within the current command buffer. This can be combined with theVK_RENDERING_CONTENTS_SECONDARY_COMMAND_BUFFERS_BIT
bit to allow draw calls to be recorded both inline and in secondary command buffers.
The contents of pRenderingInfo
must match between suspended render
pass instances and the render pass instances that resume them, other than
the presence or absence of the VK_RENDERING_RESUMING_BIT
,
VK_RENDERING_SUSPENDING_BIT
, and
VK_RENDERING_CONTENTS_SECONDARY_COMMAND_BUFFERS_BIT
flags.
No action or synchronization commands, or other render pass instances, are
allowed between suspending and resuming render pass instances.
// Provided by VK_VERSION_1_3
typedef VkFlags VkRenderingFlags;
or the equivalent
// Provided by VK_KHR_dynamic_rendering
typedef VkRenderingFlags VkRenderingFlagsKHR;
VkRenderingFlags
is a bitmask type for setting a mask of zero or more
VkRenderingFlagBits.
The VkRenderingAttachmentInfo
structure is defined as:
// Provided by VK_VERSION_1_3
typedef struct VkRenderingAttachmentInfo {
VkStructureType sType;
const void* pNext;
VkImageView imageView;
VkImageLayout imageLayout;
VkResolveModeFlagBits resolveMode;
VkImageView resolveImageView;
VkImageLayout resolveImageLayout;
VkAttachmentLoadOp loadOp;
VkAttachmentStoreOp storeOp;
VkClearValue clearValue;
} VkRenderingAttachmentInfo;
or the equivalent
// Provided by VK_KHR_dynamic_rendering
typedef VkRenderingAttachmentInfo VkRenderingAttachmentInfoKHR;
-
sType
is a VkStructureType value identifying this structure. -
pNext
isNULL
or a pointer to a structure extending this structure. -
imageView
is the image view that will be used for rendering. -
imageLayout
is the layout thatimageView
will be in during rendering. -
resolveMode
is a VkResolveModeFlagBits value defining how data written toimageView
will be resolved intoresolveImageView
. -
resolveImageView
is an image view used to write resolved data at the end of rendering. -
resolveImageLayout
is the layout thatresolveImageView
will be in during rendering. -
loadOp
is a VkAttachmentLoadOp value defining the load operation for the attachment. -
storeOp
is a VkAttachmentStoreOp value defining the store operation for the attachment. -
clearValue
is a VkClearValue structure defining values used to clearimageView
whenloadOp
isVK_ATTACHMENT_LOAD_OP_CLEAR
.
Values in imageView
are loaded and stored according to the values of
loadOp
and storeOp
, within the render area
for each device
specified in VkRenderingInfo.
If imageView
is VK_NULL_HANDLE,
and resolveMode
is not
VK_RESOLVE_MODE_EXTERNAL_FORMAT_DOWNSAMPLE_ANDROID
,
other members of this structure are ignored; writes to this attachment will
be discarded, and no load,
store, or multisample resolve operations will be performed.
If resolveMode
is VK_RESOLVE_MODE_NONE
, then
resolveImageView
is ignored.
If resolveMode
is not VK_RESOLVE_MODE_NONE
, and
resolveImageView
is not VK_NULL_HANDLE, a
render pass multisample resolve operation
is defined for the attachment subresource.
If resolveMode
is
VK_RESOLVE_MODE_EXTERNAL_FORMAT_DOWNSAMPLE_ANDROID
, and the
nullColorAttachmentWithExternalFormatResolve
limit is VK_TRUE
,
values are only undefined once load operations have completed.
The resolve mode and store operation are independent; it is valid to write both resolved and unresolved values, and equally valid to discard the unresolved values while writing the resolved ones. |
Store and resolve operations are only performed at the end of a render pass
instance that does not specify the VK_RENDERING_SUSPENDING_BIT_KHR
flag.
Load operations are only performed at the beginning of a render pass
instance that does not specify the VK_RENDERING_RESUMING_BIT_KHR
flag.
Image contents at the end of a suspended render pass instance remain defined for access by a resuming render pass instance.
If the nullColorAttachmentWithExternalFormatResolve
limit is VK_TRUE
,
and resolveMode
is
VK_RESOLVE_MODE_EXTERNAL_FORMAT_DOWNSAMPLE_ANDROID
, values in the
color attachment will be loaded from the resolve attachment at the start of
rendering, and may also be reloaded any time after a resolve occurs or the
resolve attachment is written to; if this occurs it must happen-before any
writes to the color attachment are performed which happen-after the resolve
that triggers this.
If any color component in the external format is subsampled, values will be
read from the nearest sample in the image when they are loaded.
The VkRenderingFragmentShadingRateAttachmentInfoKHR
structure is
defined as:
// Provided by VK_KHR_dynamic_rendering with VK_KHR_fragment_shading_rate
typedef struct VkRenderingFragmentShadingRateAttachmentInfoKHR {
VkStructureType sType;
const void* pNext;
VkImageView imageView;
VkImageLayout imageLayout;
VkExtent2D shadingRateAttachmentTexelSize;
} VkRenderingFragmentShadingRateAttachmentInfoKHR;
-
sType
is a VkStructureType value identifying this structure. -
pNext
isNULL
or a pointer to a structure extending this structure. -
imageView
is the image view that will be used as a fragment shading rate attachment. -
imageLayout
is the layout thatimageView
will be in during rendering. -
shadingRateAttachmentTexelSize
specifies the number of pixels corresponding to each texel inimageView
.
This structure can be included in the pNext
chain of
VkRenderingInfo to define a
fragment shading rate attachment.
If imageView
is VK_NULL_HANDLE, or if this structure is not
specified, the implementation behaves as if a valid shading rate attachment
was specified with all texels specifying a single pixel per fragment.
The VkRenderingFragmentDensityMapAttachmentInfoEXT
structure is
defined as:
// Provided by VK_KHR_dynamic_rendering with VK_EXT_fragment_density_map
typedef struct VkRenderingFragmentDensityMapAttachmentInfoEXT {
VkStructureType sType;
const void* pNext;
VkImageView imageView;
VkImageLayout imageLayout;
} VkRenderingFragmentDensityMapAttachmentInfoEXT;
-
sType
is a VkStructureType value identifying this structure. -
pNext
isNULL
or a pointer to a structure extending this structure. -
imageView
is the image view that will be used as a fragment density map attachment. -
imageLayout
is the layout thatimageView
will be in during rendering.
This structure can be included in the pNext
chain of
VkRenderingInfo to define a fragment density map.
If this structure is not included in the pNext
chain, imageView
is treated as VK_NULL_HANDLE.
To query the render area granularity for a render pass instance, call:
// Provided by VK_KHR_maintenance5
void vkGetRenderingAreaGranularityKHR(
VkDevice device,
const VkRenderingAreaInfoKHR* pRenderingAreaInfo,
VkExtent2D* pGranularity);
-
device
is the logical device that owns the render pass instance. -
pRenderingAreaInfo
is a pointer to a VkRenderingAreaInfoKHR structure specifying details of the render pass instance to query the render area granularity for. -
pGranularity
is a pointer to a VkExtent2D structure in which the granularity is returned.
The conditions leading to an optimal renderArea
are:
-
the
offset.x
member inrenderArea
is a multiple of thewidth
member of the returned VkExtent2D (the horizontal granularity). -
the
offset.y
member inrenderArea
is a multiple of theheight
member of the returned VkExtent2D (the vertical granularity). -
either the
extent.width
member inrenderArea
is a multiple of the horizontal granularity oroffset.x
+extent.width
is equal to thewidth
of each attachment used in the render pass instance. -
either the
extent.height
member inrenderArea
is a multiple of the vertical granularity oroffset.y
+extent.height
is equal to theheight
of each attachment used in the render pass instance.
The VkRenderingAreaInfoKHR
structure is defined as:
// Provided by VK_KHR_maintenance5
typedef struct VkRenderingAreaInfoKHR {
VkStructureType sType;
const void* pNext;
uint32_t viewMask;
uint32_t colorAttachmentCount;
const VkFormat* pColorAttachmentFormats;
VkFormat depthAttachmentFormat;
VkFormat stencilAttachmentFormat;
} VkRenderingAreaInfoKHR;
-
sType
is a VkStructureType value identifying this structure. -
pNext
isNULL
or a pointer to a structure extending this structure. -
viewMask
is the viewMask used for rendering. -
colorAttachmentCount
is the number of entries inpColorAttachmentFormats
-
pColorAttachmentFormats
is a pointer to an array of VkFormat values defining the format of color attachments used in the render pass instance. -
depthAttachmentFormat
is a VkFormat value defining the format of the depth attachment used in the render pass instance. -
stencilAttachmentFormat
is a VkFormat value defining the format of the stencil attachment used in the render pass instance.
The VkRenderPassStripeBeginInfoARM
structure is defined as:
// Provided by VK_ARM_render_pass_striped
typedef struct VkRenderPassStripeBeginInfoARM {
VkStructureType sType;
const void* pNext;
uint32_t stripeInfoCount;
const VkRenderPassStripeInfoARM* pStripeInfos;
} VkRenderPassStripeBeginInfoARM;
-
sType
is a VkStructureType value identifying this structure. -
pNext
isNULL
or a pointer to a structure extending this structure. -
stripeInfoCount
is the number of stripes in this render pass instance -
pStripeInfos
is a pointer to an array ofstripeInfoCount
VkRenderPassStripeInfoARM structures describing the stripes used by the render pass instance.
This structure can be included in the pNext
chain of
VkRenderPassBeginInfo
or VkRenderingInfo
to define how the render pass instance is split into stripes.
The VkRenderPassStripeInfoARM
structure is defined as:
// Provided by VK_ARM_render_pass_striped
typedef struct VkRenderPassStripeInfoARM {
VkStructureType sType;
const void* pNext;
VkRect2D stripeArea;
} VkRenderPassStripeInfoARM;
-
sType
is a VkStructureType value identifying this structure. -
pNext
isNULL
or a pointer to a structure extending this structure. -
stripeArea
is the stripe area, and is described in more detail below.
stripeArea
is the render area that is affected by this stripe of the
render pass instance.
It must be a subregion of the renderArea
of the render pass instance.
To end a render pass instance, call:
// Provided by VK_VERSION_1_3
void vkCmdEndRendering(
VkCommandBuffer commandBuffer);
or the equivalent command
// Provided by VK_KHR_dynamic_rendering
void vkCmdEndRenderingKHR(
VkCommandBuffer commandBuffer);
-
commandBuffer
is the command buffer in which to record the command.
If the value of pRenderingInfo->flags
used to begin this render pass
instance included VK_RENDERING_SUSPENDING_BIT
, then this render pass
is suspended and will be resumed later in
submission order.
For more complex rendering graphs, it is possible to pre-define a static render pass object, which as well as allowing draw commands, allows the definition of framebuffer-local dependencies between multiple subpasses. These objects have a lot of setup cost compared to vkCmdBeginRendering, but use of subpass dependencies can confer important performance benefits on some devices. |
The VkTilePropertiesQCOM
structure is defined as:
// Provided by VK_QCOM_tile_properties
typedef struct VkTilePropertiesQCOM {
VkStructureType sType;
void* pNext;
VkExtent3D tileSize;
VkExtent2D apronSize;
VkOffset2D origin;
} VkTilePropertiesQCOM;
-
sType
is a VkStructureType value identifying this structure. -
pNext
isNULL
or a pointer to a structure extending this structure. -
tileSize
is the dimensions of a tile, with width and height describing the width and height of a tile in pixels, and depth corresponding to the number of slices the tile spans. -
apronSize
is the dimension of the apron. -
origin
is the top-left corner of the first tile in attachment space.
All tiles will be tightly packed around the first tile, with edges being multiples of tile width and/or height from the origin.
Reported value for |
To query the tile properties when using dynamic rendering, call:
// Provided by VK_QCOM_tile_properties
VkResult vkGetDynamicRenderingTilePropertiesQCOM(
VkDevice device,
const VkRenderingInfo* pRenderingInfo,
VkTilePropertiesQCOM* pProperties);
-
device
is a logical device associated with the render pass. -
pRenderingInfo
is a pointer to the VkRenderingInfo structure specifying details of the render pass instance in dynamic rendering. -
pProperties
is a pointer to a VkTilePropertiesQCOM structure in which the properties are returned.
Render Pass Objects
A render pass object represents a collection of attachments, subpasses, and dependencies between the subpasses, and describes how the attachments are used over the course of the subpasses.
Render passes are represented by VkRenderPass
handles:
// Provided by VK_VERSION_1_0
VK_DEFINE_NON_DISPATCHABLE_HANDLE(VkRenderPass)
An attachment description describes the properties of an attachment including its format, sample count, and how its contents are treated at the beginning and end of each render pass instance.
A subpass represents a phase of rendering that reads and writes a subset of the attachments in a render pass. Rendering commands are recorded into a particular subpass of a render pass instance.
A subpass description describes the subset of attachments that is involved in the execution of a subpass. Each subpass can read from some attachments as input attachments, write to some as color attachments or depth/stencil attachments, perform shader resolve operations to color_attachments or depth/stencil_attachments, and perform multisample resolve operations to resolve attachments. A subpass description can also include a set of preserve attachments, which are attachments that are not read or written by the subpass but whose contents must be preserved throughout the subpass.
A subpass uses an attachment if the attachment is a color, depth/stencil,
resolve,
depth/stencil resolve,
fragment shading rate,
or input attachment for that subpass (as determined by the
pColorAttachments
, pDepthStencilAttachment
,
pResolveAttachments
,
VkSubpassDescriptionDepthStencilResolve::pDepthStencilResolveAttachment
,
VkFragmentShadingRateAttachmentInfoKHR::pFragmentShadingRateAttachment->attachment
,
and pInputAttachments
members of VkSubpassDescription,
respectively).
A subpass does not use an attachment if that attachment is preserved by the
subpass.
The first use of an attachment is in the lowest numbered subpass that uses
that attachment.
Similarly, the last use of an attachment is in the highest numbered
subpass that uses that attachment.
The subpasses in a render pass all render to the same dimensions, and fragments for pixel (x,y,layer) in one subpass can only read attachment contents written by previous subpasses at that same (x,y,layer) location. For multi-pixel fragments, the pixel read from an input attachment is selected from the pixels covered by that fragment in an implementation-dependent manner. However, this selection must be made consistently for any fragment with the same shading rate for the lifetime of the VkDevice.
By describing a complete set of subpasses in advance, render passes provide the implementation an opportunity to optimize the storage and transfer of attachment data between subpasses. In practice, this means that subpasses with a simple framebuffer-space dependency may be merged into a single tiled rendering pass, keeping the attachment data on-chip for the duration of a render pass instance. However, it is also quite common for a render pass to only contain a single subpass. |
Subpass dependencies describe execution and memory dependencies between subpasses.
A subpass dependency chain is a sequence of subpass dependencies in a render pass, where the source subpass of each subpass dependency (after the first) equals the destination subpass of the previous dependency.
Execution of subpasses may overlap or execute out of order with regards to other subpasses, unless otherwise enforced by an execution dependency. Each subpass only respects submission order for commands recorded in the same subpass, and the vkCmdBeginRenderPass and vkCmdEndRenderPass commands that delimit the render pass - commands within other subpasses are not included. This affects most other implicit ordering guarantees.
A render pass describes the structure of subpasses and attachments
independent of any specific image views for the attachments.
The specific image views that will be used for the attachments, and their
dimensions, are specified in VkFramebuffer
objects.
Framebuffers are created with respect to a specific render pass that the
framebuffer is compatible with (see Render Pass Compatibility).
Collectively, a render pass and a framebuffer define the complete render
target state for one or more subpasses as well as the algorithmic
dependencies between the subpasses.
The various pipeline stages of the drawing commands for a given subpass may execute concurrently and/or out of order, both within and across drawing commands, whilst still respecting pipeline order. However for a given (x,y,layer,sample) sample location, certain per-sample operations are performed in rasterization order.
VK_ATTACHMENT_UNUSED
is a constant indicating that a render pass
attachment is not used.
#define VK_ATTACHMENT_UNUSED (~0U)
Render Pass Creation
To create a render pass, call:
// Provided by VK_VERSION_1_0
VkResult vkCreateRenderPass(
VkDevice device,
const VkRenderPassCreateInfo* pCreateInfo,
const VkAllocationCallbacks* pAllocator,
VkRenderPass* pRenderPass);
-
device
is the logical device that creates the render pass. -
pCreateInfo
is a pointer to a VkRenderPassCreateInfo structure describing the parameters of the render pass. -
pAllocator
controls host memory allocation as described in the Memory Allocation chapter. -
pRenderPass
is a pointer to a VkRenderPass handle in which the resulting render pass object is returned.
The VkRenderPassCreateInfo
structure is defined as:
// Provided by VK_VERSION_1_0
typedef struct VkRenderPassCreateInfo {
VkStructureType sType;
const void* pNext;
VkRenderPassCreateFlags flags;
uint32_t attachmentCount;
const VkAttachmentDescription* pAttachments;
uint32_t subpassCount;
const VkSubpassDescription* pSubpasses;
uint32_t dependencyCount;
const VkSubpassDependency* pDependencies;
} VkRenderPassCreateInfo;
-
sType
is a VkStructureType value identifying this structure. -
pNext
isNULL
or a pointer to a structure extending this structure. -
flags
is a bitmask of VkRenderPassCreateFlagBits -
attachmentCount
is the number of attachments used by this render pass. -
pAttachments
is a pointer to an array ofattachmentCount
VkAttachmentDescription structures describing the attachments used by the render pass. -
subpassCount
is the number of subpasses to create. -
pSubpasses
is a pointer to an array ofsubpassCount
VkSubpassDescription structures describing each subpass. -
dependencyCount
is the number of memory dependencies between pairs of subpasses. -
pDependencies
is a pointer to an array ofdependencyCount
VkSubpassDependency structures describing dependencies between pairs of subpasses.
Care should be taken to avoid a data race here; if any subpasses access attachments with overlapping memory locations, and one of those accesses is a write, a subpass dependency needs to be included between them. |
Bits which can be set in VkRenderPassCreateInfo::flags
,
describing additional properties of the render pass, are:
// Provided by VK_VERSION_1_0
typedef enum VkRenderPassCreateFlagBits {
// Provided by VK_QCOM_render_pass_transform
VK_RENDER_PASS_CREATE_TRANSFORM_BIT_QCOM = 0x00000002,
} VkRenderPassCreateFlagBits;
-
VK_RENDER_PASS_CREATE_TRANSFORM_BIT_QCOM
specifies that the created render pass is compatible with render pass transform.
// Provided by VK_VERSION_1_0
typedef VkFlags VkRenderPassCreateFlags;
VkRenderPassCreateFlags
is a bitmask type for setting a mask of zero
or more VkRenderPassCreateFlagBits.
If the VkRenderPassCreateInfo::pNext
chain includes a
VkRenderPassMultiviewCreateInfo
structure, then that structure
includes an array of view masks, view offsets, and correlation masks for the
render pass.
The VkRenderPassMultiviewCreateInfo
structure is defined as:
// Provided by VK_VERSION_1_1
typedef struct VkRenderPassMultiviewCreateInfo {
VkStructureType sType;
const void* pNext;
uint32_t subpassCount;
const uint32_t* pViewMasks;
uint32_t dependencyCount;
const int32_t* pViewOffsets;
uint32_t correlationMaskCount;
const uint32_t* pCorrelationMasks;
} VkRenderPassMultiviewCreateInfo;
or the equivalent
// Provided by VK_KHR_multiview
typedef VkRenderPassMultiviewCreateInfo VkRenderPassMultiviewCreateInfoKHR;
-
sType
is a VkStructureType value identifying this structure. -
pNext
isNULL
or a pointer to a structure extending this structure. -
subpassCount
is zero or the number of subpasses in the render pass. -
pViewMasks
is a pointer to an array ofsubpassCount
view masks, where each mask is a bitfield of view indices describing which views rendering is broadcast to in each subpass, when multiview is enabled. IfsubpassCount
is zero, each view mask is treated as zero. -
dependencyCount
is zero or the number of dependencies in the render pass. -
pViewOffsets
is a pointer to an array ofdependencyCount
view offsets, one for each dependency. IfdependencyCount
is zero, each dependency’s view offset is treated as zero. Each view offset controls which views in the source subpass the views in the destination subpass depend on. -
correlationMaskCount
is zero or the number of correlation masks. -
pCorrelationMasks
is a pointer to an array ofcorrelationMaskCount
view masks indicating sets of views that may be more efficient to render concurrently.
When a subpass uses a non-zero view mask, multiview functionality is
considered to be enabled.
Multiview is all-or-nothing for a render pass - that is, either all
subpasses must have a non-zero view mask (though some subpasses may have
only one view) or all must be zero.
Multiview causes all drawing and clear commands in the subpass to behave as
if they were broadcast to each view, where a view is represented by one
layer of the framebuffer attachments.
All draws and clears are broadcast to each view index whose bit is set in
the view mask.
The view index is provided in the ViewIndex
shader input variable, and
color, depth/stencil, and input attachments all read/write the layer of the
framebuffer corresponding to the view index.
If the view mask is zero for all subpasses, multiview is considered to be disabled and all drawing commands execute normally, without this additional broadcasting.
Some implementations may not support multiview in conjunction with mesh shaders, geometry shaders or tessellation shaders.
When multiview is enabled, the VK_DEPENDENCY_VIEW_LOCAL_BIT
bit in a
dependency can be used to express a view-local dependency, meaning that
each view in the destination subpass depends on a single view in the source
subpass.
Unlike pipeline barriers, a subpass dependency can potentially have a
different view mask in the source subpass and the destination subpass.
If the dependency is view-local, then each view (dstView) in the
destination subpass depends on the view dstView +
pViewOffsets
[dependency] in the source subpass.
If there is not such a view in the source subpass, then this dependency does
not affect that view in the destination subpass.
If the dependency is not view-local, then all views in the destination
subpass depend on all views in the source subpass, and the view offset is
ignored.
A non-zero view offset is not allowed in a self-dependency.
The elements of pCorrelationMasks
are a set of masks of views
indicating that views in the same mask may exhibit spatial coherency
between the views, making it more efficient to render them concurrently.
Correlation masks must not have a functional effect on the results of the
multiview rendering.
When multiview is enabled, at the beginning of each subpass all non-render pass state is undefined. In particular, each time vkCmdBeginRenderPass or vkCmdNextSubpass is called the graphics pipeline must be bound, any relevant descriptor sets or vertex/index buffers must be bound, and any relevant dynamic state or push constants must be set before they are used.
A multiview subpass can declare that its shaders will write per-view
attributes for all views in a single invocation, by setting the
VK_SUBPASS_DESCRIPTION_PER_VIEW_ATTRIBUTES_BIT_NVX
bit in the subpass
description.
The only supported per-view attributes are position and viewport mask, and
per-view position and viewport masks are written to output array variables
decorated with PositionPerViewNV
and ViewportMaskPerViewNV
,
respectively.
If VK_NV_viewport_array2
is not supported and enabled,
ViewportMaskPerViewNV
must not be used.
Values written to elements of PositionPerViewNV
and
ViewportMaskPerViewNV
must not depend on the ViewIndex
.
The shader must also write to an output variable decorated with
Position
, and the value written to Position
must equal the value
written to PositionPerViewNV
[ViewIndex
].
Similarly, if ViewportMaskPerViewNV
is written to then the shader must
also write to an output variable decorated with ViewportMaskNV
, and the
value written to ViewportMaskNV
must equal the value written to
ViewportMaskPerViewNV
[ViewIndex
].
Implementations will either use values taken from Position
and
ViewportMaskNV
and invoke the shader once for each view, or will use
values taken from PositionPerViewNV
and ViewportMaskPerViewNV
and
invoke the shader fewer times.
The values written to Position
and ViewportMaskNV
must not depend
on the values written to PositionPerViewNV
and
ViewportMaskPerViewNV
, or vice versa (to allow compilers to eliminate
the unused outputs).
All attributes that do not have *PerViewNV
counterparts must not depend
on ViewIndex
.
Per-view attributes are all-or-nothing for a subpass.
That is, all pipelines compiled against a subpass that includes the
VK_SUBPASS_DESCRIPTION_PER_VIEW_ATTRIBUTES_BIT_NVX
bit must write
per-view attributes to the *PerViewNV[]
shader outputs, in addition to the
non-per-view (e.g. Position
) outputs.
Pipelines compiled against a subpass that does not include this bit must
not include the *PerViewNV[]
outputs in their interfaces.
The VkMultiviewPerViewAttributesInfoNVX
structure is defined as:
// Provided by VK_KHR_dynamic_rendering with VK_NVX_multiview_per_view_attributes
typedef struct VkMultiviewPerViewAttributesInfoNVX {
VkStructureType sType;
const void* pNext;
VkBool32 perViewAttributes;
VkBool32 perViewAttributesPositionXOnly;
} VkMultiviewPerViewAttributesInfoNVX;
-
sType
is a VkStructureType value identifying this structure. -
pNext
isNULL
or a pointer to a structure extending this structure. -
perViewAttributes
specifies that shaders compiled for this pipeline write the attributes for all views in a single invocation of each vertex processing stage. All pipelines executed within a render pass instance that includes this bit must write per-view attributes to the*PerViewNV[]
shader outputs, in addition to the non-per-view (e.g.Position
) outputs. -
perViewAttributesPositionXOnly
specifies that shaders compiled for this pipeline use per-view positions which only differ in value in the x component. Per-view viewport mask can also be used.
When dynamic render pass instances are being used, instead of specifying
VK_SUBPASS_DESCRIPTION_PER_VIEW_ATTRIBUTES_BIT_NVX
or
VK_SUBPASS_DESCRIPTION_PER_VIEW_POSITION_X_ONLY_BIT_NVX
in the subpass
description flags, the per-attribute properties of the render pass instance
must be specified by the VkMultiviewPerViewAttributesInfoNVX
structure Include the VkMultiviewPerViewAttributesInfoNVX
structure in
the pNext
chain of VkGraphicsPipelineCreateInfo when creating a
graphics pipeline for dynamic rendering, VkRenderingInfo when starting
a dynamic render pass instance, and VkCommandBufferInheritanceInfo
when specifying the dynamic render pass instance parameters for secondary
command buffers.
If the VkRenderPassCreateInfo::pNext
chain includes a
VkRenderPassFragmentDensityMapCreateInfoEXT
structure, then that
structure includes a fragment density map attachment for the render pass.
The VkRenderPassFragmentDensityMapCreateInfoEXT
structure is defined
as:
// Provided by VK_EXT_fragment_density_map
typedef struct VkRenderPassFragmentDensityMapCreateInfoEXT {
VkStructureType sType;
const void* pNext;
VkAttachmentReference fragmentDensityMapAttachment;
} VkRenderPassFragmentDensityMapCreateInfoEXT;
-
sType
is a VkStructureType value identifying this structure. -
pNext
isNULL
or a pointer to a structure extending this structure. -
fragmentDensityMapAttachment
is the fragment density map to use for the render pass.
The fragment density map is read at an implementation-dependent time with
the following constraints determined by the attachment’s image view
flags
:
-
VK_IMAGE_VIEW_CREATE_FRAGMENT_DENSITY_MAP_DYNAMIC_BIT_EXT
specifies that the fragment density map will be read by the device duringVK_PIPELINE_STAGE_FRAGMENT_DENSITY_PROCESS_BIT_EXT
-
VK_IMAGE_VIEW_CREATE_FRAGMENT_DENSITY_MAP_DEFERRED_BIT_EXT
specifies that the fragment density map will be read by the host during vkEndCommandBuffer of the primary command buffer that the render pass is recorded into -
Otherwise the fragment density map will be read by the host during vkCmdBeginRenderPass
The fragment density map may additionally be read by the device during
VK_PIPELINE_STAGE_FRAGMENT_DENSITY_PROCESS_BIT_EXT
for any mode.
If this structure is not present, it is as if
fragmentDensityMapAttachment
was given as VK_ATTACHMENT_UNUSED
.
The VkAttachmentDescription
structure is defined as:
// Provided by VK_VERSION_1_0
typedef struct VkAttachmentDescription {
VkAttachmentDescriptionFlags flags;
VkFormat format;
VkSampleCountFlagBits samples;
VkAttachmentLoadOp loadOp;
VkAttachmentStoreOp storeOp;
VkAttachmentLoadOp stencilLoadOp;
VkAttachmentStoreOp stencilStoreOp;
VkImageLayout initialLayout;
VkImageLayout finalLayout;
} VkAttachmentDescription;
-
flags
is a bitmask of VkAttachmentDescriptionFlagBits specifying additional properties of the attachment. -
format
is a VkFormat value specifying the format of the image view that will be used for the attachment. -
samples
is a VkSampleCountFlagBits value specifying the number of samples of the image. -
loadOp
is a VkAttachmentLoadOp value specifying how the contents of color and depth components of the attachment are treated at the beginning of the subpass where it is first used. -
storeOp
is a VkAttachmentStoreOp value specifying how the contents of color and depth components of the attachment are treated at the end of the subpass where it is last used. -
stencilLoadOp
is a VkAttachmentLoadOp value specifying how the contents of stencil components of the attachment are treated at the beginning of the subpass where it is first used. -
stencilStoreOp
is a VkAttachmentStoreOp value specifying how the contents of stencil components of the attachment are treated at the end of the last subpass where it is used. -
initialLayout
is the layout the attachment image subresource will be in when a render pass instance begins. -
finalLayout
is the layout the attachment image subresource will be transitioned to when a render pass instance ends.
If the attachment uses a color format, then loadOp
and storeOp
are used, and stencilLoadOp
and stencilStoreOp
are ignored.
If the format has depth and/or stencil components, loadOp
and
storeOp
apply only to the depth data, while stencilLoadOp
and
stencilStoreOp
define how the stencil data is handled.
loadOp
and stencilLoadOp
define the
load operations for the attachment.
storeOp
and stencilStoreOp
define the
store operations for the attachment.
If an attachment is not used by any subpass, loadOp
, storeOp
,
stencilStoreOp
, and stencilLoadOp
will be ignored for that
attachment, and no load or store ops will be performed.
However, any transition specified by initialLayout
and
finalLayout
will still be executed.
If flags
includes VK_ATTACHMENT_DESCRIPTION_MAY_ALIAS_BIT
, then
the attachment is treated as if it shares physical memory with another
attachment in the same render pass.
This information limits the ability of the implementation to reorder certain
operations (like layout transitions and the loadOp
) such that it is
not improperly reordered against other uses of the same physical memory via
a different attachment.
This is described in more detail below.
If a render pass uses multiple attachments that alias the same device
memory, those attachments must each include the
VK_ATTACHMENT_DESCRIPTION_MAY_ALIAS_BIT
bit in their attachment
description flags.
Attachments aliasing the same memory occurs in multiple ways:
-
Multiple attachments being assigned the same image view as part of framebuffer creation.
-
Attachments using distinct image views that correspond to the same image subresource of an image.
-
Attachments using views of distinct image subresources which are bound to overlapping memory ranges.
Render passes must include subpass dependencies (either directly or via a
subpass dependency chain) between any two subpasses that operate on the same
attachment or aliasing attachments and those subpass dependencies must
include execution and memory dependencies separating uses of the aliases, if
at least one of those subpasses writes to one of the aliases.
These dependencies must not include the |
Multiple attachments that alias the same memory must not be used in a single subpass. A given attachment index must not be used multiple times in a single subpass, with one exception: two subpass attachments can use the same attachment index if at least one use is as an input attachment and neither use is as a resolve or preserve attachment. In other words, the same view can be used simultaneously as an input and color or depth/stencil attachment, but must not be used as multiple color or depth/stencil attachments nor as resolve or preserve attachments.
If a set of attachments alias each other, then all except the first to be
used in the render pass must use an initialLayout
of
VK_IMAGE_LAYOUT_UNDEFINED
, since the earlier uses of the other aliases
make their contents undefined.
Once an alias has been used and a different alias has been used after it,
the first alias must not be used in any later subpasses.
However, an application can assign the same image view to multiple aliasing
attachment indices, which allows that image view to be used multiple times
even if other aliases are used in between.
Once an attachment needs the |
Bits which can be set in VkAttachmentDescription::flags
,
describing additional properties of the attachment, are:
// Provided by VK_VERSION_1_0
typedef enum VkAttachmentDescriptionFlagBits {
VK_ATTACHMENT_DESCRIPTION_MAY_ALIAS_BIT = 0x00000001,
} VkAttachmentDescriptionFlagBits;
-
VK_ATTACHMENT_DESCRIPTION_MAY_ALIAS_BIT
specifies that the attachment aliases the same device memory as other attachments.
// Provided by VK_VERSION_1_0
typedef VkFlags VkAttachmentDescriptionFlags;
VkAttachmentDescriptionFlags
is a bitmask type for setting a mask of
zero or more VkAttachmentDescriptionFlagBits.
The VkRenderPassInputAttachmentAspectCreateInfo
structure is defined
as:
// Provided by VK_VERSION_1_1
typedef struct VkRenderPassInputAttachmentAspectCreateInfo {
VkStructureType sType;
const void* pNext;
uint32_t aspectReferenceCount;
const VkInputAttachmentAspectReference* pAspectReferences;
} VkRenderPassInputAttachmentAspectCreateInfo;
or the equivalent
// Provided by VK_KHR_maintenance2
typedef VkRenderPassInputAttachmentAspectCreateInfo VkRenderPassInputAttachmentAspectCreateInfoKHR;
-
sType
is a VkStructureType value identifying this structure. -
pNext
isNULL
or a pointer to a structure extending this structure. -
aspectReferenceCount
is the number of elements in thepAspectReferences
array. -
pAspectReferences
is a pointer to an array ofaspectReferenceCount
VkInputAttachmentAspectReference structures containing a mask describing which aspect(s) can be accessed for a given input attachment within a given subpass.
To specify which aspects of an input attachment can be read, add a
VkRenderPassInputAttachmentAspectCreateInfo structure to the
pNext
chain of the VkRenderPassCreateInfo structure:
An application can access any aspect of an input attachment that does not
have a specified aspect mask in the pAspectReferences
array.
Otherwise, an application must not access aspect(s) of an input attachment
other than those in its specified aspect mask.
The VkInputAttachmentAspectReference
structure is defined as:
// Provided by VK_VERSION_1_1
typedef struct VkInputAttachmentAspectReference {
uint32_t subpass;
uint32_t inputAttachmentIndex;
VkImageAspectFlags aspectMask;
} VkInputAttachmentAspectReference;
or the equivalent
// Provided by VK_KHR_maintenance2
typedef VkInputAttachmentAspectReference VkInputAttachmentAspectReferenceKHR;
-
subpass
is an index into thepSubpasses
array of the parentVkRenderPassCreateInfo
structure. -
inputAttachmentIndex
is an index into thepInputAttachments
of the specified subpass. -
aspectMask
is a mask of which aspect(s) can be accessed within the specified subpass.
This structure specifies an aspect mask for a specific input attachment of a specific subpass in the render pass.
subpass
and inputAttachmentIndex
index into the render pass as:
pCreateInfo->pSubpasses[subpass].pInputAttachments[inputAttachmentIndex]
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;
-
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 ofcolorAttachmentCount
VkAttachmentReference structures defining the color attachments for this subpass and their layouts. -
pResolveAttachments
isNULL
or a pointer to an array ofcolorAttachmentCount
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 ofpreserveAttachmentCount
render pass attachment indices identifying attachments that are not used by this subpass, but whose contents must be preserved throughout the subpass.
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 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.
Bits which can be set in VkSubpassDescription::flags
,
specifying usage of the subpass, are:
// Provided by VK_VERSION_1_0
typedef enum VkSubpassDescriptionFlagBits {
// Provided by VK_NVX_multiview_per_view_attributes
VK_SUBPASS_DESCRIPTION_PER_VIEW_ATTRIBUTES_BIT_NVX = 0x00000001,
// Provided by VK_NVX_multiview_per_view_attributes
VK_SUBPASS_DESCRIPTION_PER_VIEW_POSITION_X_ONLY_BIT_NVX = 0x00000002,
// Provided by VK_QCOM_render_pass_shader_resolve
VK_SUBPASS_DESCRIPTION_FRAGMENT_REGION_BIT_QCOM = 0x00000004,
// Provided by VK_QCOM_render_pass_shader_resolve
VK_SUBPASS_DESCRIPTION_SHADER_RESOLVE_BIT_QCOM = 0x00000008,
// Provided by VK_EXT_rasterization_order_attachment_access
VK_SUBPASS_DESCRIPTION_RASTERIZATION_ORDER_ATTACHMENT_COLOR_ACCESS_BIT_EXT = 0x00000010,
// Provided by VK_EXT_rasterization_order_attachment_access
VK_SUBPASS_DESCRIPTION_RASTERIZATION_ORDER_ATTACHMENT_DEPTH_ACCESS_BIT_EXT = 0x00000020,
// Provided by VK_EXT_rasterization_order_attachment_access
VK_SUBPASS_DESCRIPTION_RASTERIZATION_ORDER_ATTACHMENT_STENCIL_ACCESS_BIT_EXT = 0x00000040,
// Provided by VK_EXT_legacy_dithering
VK_SUBPASS_DESCRIPTION_ENABLE_LEGACY_DITHERING_BIT_EXT = 0x00000080,
// Provided by VK_ARM_rasterization_order_attachment_access
VK_SUBPASS_DESCRIPTION_RASTERIZATION_ORDER_ATTACHMENT_COLOR_ACCESS_BIT_ARM = VK_SUBPASS_DESCRIPTION_RASTERIZATION_ORDER_ATTACHMENT_COLOR_ACCESS_BIT_EXT,
// Provided by VK_ARM_rasterization_order_attachment_access
VK_SUBPASS_DESCRIPTION_RASTERIZATION_ORDER_ATTACHMENT_DEPTH_ACCESS_BIT_ARM = VK_SUBPASS_DESCRIPTION_RASTERIZATION_ORDER_ATTACHMENT_DEPTH_ACCESS_BIT_EXT,
// Provided by VK_ARM_rasterization_order_attachment_access
VK_SUBPASS_DESCRIPTION_RASTERIZATION_ORDER_ATTACHMENT_STENCIL_ACCESS_BIT_ARM = VK_SUBPASS_DESCRIPTION_RASTERIZATION_ORDER_ATTACHMENT_STENCIL_ACCESS_BIT_EXT,
} VkSubpassDescriptionFlagBits;
-
VK_SUBPASS_DESCRIPTION_PER_VIEW_ATTRIBUTES_BIT_NVX
specifies that shaders compiled for this subpass write the attributes for all views in a single invocation of each pre-rasterization shader stage. All pipelines compiled against a subpass that includes this bit must write per-view attributes to the*PerViewNV[]
shader outputs, in addition to the non-per-view (e.g.Position
) outputs. -
VK_SUBPASS_DESCRIPTION_PER_VIEW_POSITION_X_ONLY_BIT_NVX
specifies that shaders compiled for this subpass use per-view positions which only differ in value in the x component. Per-view viewport mask can also be used. -
VK_SUBPASS_DESCRIPTION_FRAGMENT_REGION_BIT_QCOM
specifies that the framebuffer region is the fragment region, that is, the minimum region dependencies are by pixel rather than by sample, such that any fragment shader invocation can access any sample associated with that fragment shader invocation. -
VK_SUBPASS_DESCRIPTION_SHADER_RESOLVE_BIT_QCOM
specifies that the subpass performs shader resolve operations. -
VK_SUBPASS_DESCRIPTION_RASTERIZATION_ORDER_ATTACHMENT_COLOR_ACCESS_BIT_EXT
specifies that this subpass supports pipelines created withVK_PIPELINE_COLOR_BLEND_STATE_CREATE_RASTERIZATION_ORDER_ATTACHMENT_ACCESS_BIT_EXT
. -
VK_SUBPASS_DESCRIPTION_RASTERIZATION_ORDER_ATTACHMENT_DEPTH_ACCESS_BIT_EXT
specifies that this subpass supports pipelines created withVK_PIPELINE_DEPTH_STENCIL_STATE_CREATE_RASTERIZATION_ORDER_ATTACHMENT_DEPTH_ACCESS_BIT_EXT
. -
VK_SUBPASS_DESCRIPTION_RASTERIZATION_ORDER_ATTACHMENT_STENCIL_ACCESS_BIT_EXT
specifies that this subpass supports pipelines created withVK_PIPELINE_DEPTH_STENCIL_STATE_CREATE_RASTERIZATION_ORDER_ATTACHMENT_STENCIL_ACCESS_BIT_EXT
. -
VK_SUBPASS_DESCRIPTION_ENABLE_LEGACY_DITHERING_BIT_EXT
specifies that Legacy Dithering is enabled for this subpass.
Shader resolve operations allow for custom resolve operations, but overdrawing pixels may have a performance and/or power cost. Furthermore, since the content of any depth stencil attachment or color attachment is undefined at the beginning of a shader resolve subpass, any depth testing, stencil testing, or blending operation which sources these undefined values also has undefined result value. |
// Provided by VK_VERSION_1_0
typedef VkFlags VkSubpassDescriptionFlags;
VkSubpassDescriptionFlags
is a bitmask type for setting a mask of zero
or more VkSubpassDescriptionFlagBits.
The VkAttachmentReference
structure is defined as:
// Provided by VK_VERSION_1_0
typedef struct VkAttachmentReference {
uint32_t attachment;
VkImageLayout layout;
} VkAttachmentReference;
-
attachment
is either an integer value identifying an attachment at the corresponding index in VkRenderPassCreateInfo::pAttachments
, orVK_ATTACHMENT_UNUSED
to signify that this attachment is not used. -
layout
is a VkImageLayout value specifying the layout the attachment uses during the subpass.
VK_SUBPASS_EXTERNAL
is a special subpass index value expanding
synchronization scope outside a subpass.
It is described in more detail by VkSubpassDependency.
#define VK_SUBPASS_EXTERNAL (~0U)
The VkSubpassDependency
structure is defined as:
// Provided by VK_VERSION_1_0
typedef struct VkSubpassDependency {
uint32_t srcSubpass;
uint32_t dstSubpass;
VkPipelineStageFlags srcStageMask;
VkPipelineStageFlags dstStageMask;
VkAccessFlags srcAccessMask;
VkAccessFlags dstAccessMask;
VkDependencyFlags dependencyFlags;
} VkSubpassDependency;
-
srcSubpass
is the subpass index of the first subpass in the dependency, orVK_SUBPASS_EXTERNAL
. -
dstSubpass
is the subpass index of the second subpass in the dependency, orVK_SUBPASS_EXTERNAL
. -
srcStageMask
is a bitmask of VkPipelineStageFlagBits specifying the source stage mask. -
dstStageMask
is a bitmask of VkPipelineStageFlagBits specifying the destination stage mask -
srcAccessMask
is a bitmask of VkAccessFlagBits specifying a source access mask. -
dstAccessMask
is a bitmask of VkAccessFlagBits specifying a destination access mask. -
dependencyFlags
is a bitmask of VkDependencyFlagBits.
If srcSubpass
is equal to dstSubpass
then the
VkSubpassDependency does not directly define a
dependency.
Instead, it enables pipeline barriers to be used in a render pass instance
within the identified subpass, where the scopes of one pipeline barrier
must be a subset of those described by one subpass dependency.
Subpass dependencies specified in this way that include
framebuffer-space stages in the
srcStageMask
must only include
framebuffer-space stages in
dstStageMask
, and must include VK_DEPENDENCY_BY_REGION_BIT
.
When a subpass dependency is specified in this way for a subpass that has
more than one view in its view mask, its dependencyFlags
must include
VK_DEPENDENCY_VIEW_LOCAL_BIT
.
If srcSubpass
and dstSubpass
are not equal, when a render pass
instance which includes a subpass dependency is submitted to a queue, it
defines a dependency between the subpasses
identified by srcSubpass
and dstSubpass
.
If srcSubpass
is equal to VK_SUBPASS_EXTERNAL
, the first
synchronization scope includes
commands that occur earlier in submission order than the vkCmdBeginRenderPass used to begin the render pass
instance.
Otherwise, the first set of commands includes all commands submitted as part
of the subpass instance identified by srcSubpass
and any
load, store, or multisample resolve
operations on attachments used in srcSubpass
.
In either case, the first synchronization scope is limited to operations on
the pipeline stages determined by the
source stage mask specified by
srcStageMask
.
If dstSubpass
is equal to VK_SUBPASS_EXTERNAL
, the second
synchronization scope includes
commands that occur later in submission order than the vkCmdEndRenderPass used to end the render pass
instance.
Otherwise, the second set of commands includes all commands submitted as
part of the subpass instance identified by dstSubpass
and any
load, store, and multisample resolve
operations on attachments used in dstSubpass
.
In either case, the second synchronization scope is limited to operations on
the pipeline stages determined by the
destination stage mask specified
by dstStageMask
.
The first access scope is
limited to accesses in the pipeline stages determined by the
source stage mask specified by
srcStageMask
.
It is also limited to access types in the source access mask specified by srcAccessMask
.
The second access scope is
limited to accesses in the pipeline stages determined by the
destination stage mask specified
by dstStageMask
.
It is also limited to access types in the destination access mask specified by dstAccessMask
.
The availability and visibility operations defined by a subpass dependency affect the execution of image layout transitions within the render pass.
For non-attachment resources, the memory dependency expressed by subpass
dependency is nearly identical to that of a VkMemoryBarrier (with
matching For attachments however, subpass dependencies work more like a
VkImageMemoryBarrier defined similarly to the VkMemoryBarrier
above, the queue family indices set to
|
When multiview is enabled, the execution of the multiple views of one
subpass may not occur simultaneously or even back-to-back, and rather may
be interleaved with the execution of other subpasses.
The load and store operations apply to attachments on a per-view basis.
For example, an attachment using VK_ATTACHMENT_LOAD_OP_CLEAR
will have
each view cleared on first use, but the first use of one view may be
temporally distant from the first use of another view.
A good mental model for multiview is to think of a multiview subpass as if it were a collection of individual (per-view) subpasses that are logically grouped together and described as a single multiview subpass in the API. Similarly, a multiview attachment can be thought of like several individual attachments that happen to be layers in a single image. A view-local dependency between two multiview subpasses acts like a set of one-to-one dependencies between corresponding pairs of per-view subpasses. A view-global dependency between two multiview subpasses acts like a set of N × M dependencies between all pairs of per-view subpasses in the source and destination. Thus, it is a more compact representation which also makes clear the commonality and reuse that is present between views in a subpass. This interpretation motivates the answers to questions like “when does the load op apply” - it is on the first use of each view of an attachment, as if each view was a separate attachment. The content of each view follows the description in attachment content behavior. In particular, if an attachment is preserved, all views within the attachment are preserved. |
If any two subpasses of a render pass activate transform feedback to the same bound transform feedback buffers, a subpass dependency must be included (either directly or via some intermediate subpasses) between them.
If there is no subpass dependency from VK_SUBPASS_EXTERNAL
to the
first subpass that uses an attachment, then an implicit subpass dependency
exists from VK_SUBPASS_EXTERNAL
to the first subpass it is used in.
The implicit subpass dependency only exists if there exists an automatic
layout transition away from initialLayout
.
The subpass dependency operates as if defined with the following parameters:
VkSubpassDependency implicitDependency = {
.srcSubpass = VK_SUBPASS_EXTERNAL,
.dstSubpass = firstSubpass, // First subpass attachment is used in
.srcStageMask = VK_PIPELINE_STAGE_NONE,
.dstStageMask = VK_PIPELINE_STAGE_ALL_COMMANDS_BIT,
.srcAccessMask = 0,
.dstAccessMask = VK_ACCESS_INPUT_ATTACHMENT_READ_BIT |
VK_ACCESS_COLOR_ATTACHMENT_READ_BIT |
VK_ACCESS_COLOR_ATTACHMENT_WRITE_BIT |
VK_ACCESS_DEPTH_STENCIL_ATTACHMENT_READ_BIT |
VK_ACCESS_DEPTH_STENCIL_ATTACHMENT_WRITE_BIT,
.dependencyFlags = 0
};
Similarly, if there is no subpass dependency from the last subpass that uses
an attachment to VK_SUBPASS_EXTERNAL
, then an implicit subpass
dependency exists from the last subpass it is used in to
VK_SUBPASS_EXTERNAL
.
The implicit subpass dependency only exists if there exists an automatic
layout transition into finalLayout
.
The subpass dependency operates as if defined with the following parameters:
VkSubpassDependency implicitDependency = {
.srcSubpass = lastSubpass, // Last subpass attachment is used in
.dstSubpass = VK_SUBPASS_EXTERNAL,
.srcStageMask = VK_PIPELINE_STAGE_ALL_COMMANDS_BIT,
.dstStageMask = VK_PIPELINE_STAGE_NONE,
.srcAccessMask = VK_ACCESS_COLOR_ATTACHMENT_WRITE_BIT |
VK_ACCESS_DEPTH_STENCIL_ATTACHMENT_WRITE_BIT,
.dstAccessMask = 0,
.dependencyFlags = 0
};
As subpasses may overlap or execute out of order with regards to other subpasses unless a subpass dependency chain describes otherwise, the layout transitions required between subpasses cannot be known to an application. Instead, an application provides the layout that each attachment must be in at the start and end of a render pass, and the layout it must be in during each subpass it is used in. The implementation then must execute layout transitions between subpasses in order to guarantee that the images are in the layouts required by each subpass, and in the final layout at the end of the render pass.
Automatic layout transitions apply to the entire image subresource attached
to the framebuffer.
If
multiview is not enabled and
the attachment is a view of a 1D or 2D image, the automatic layout
transitions apply to the number of layers specified by
VkFramebufferCreateInfo::layers
.
If multiview is enabled and the attachment is a view of a 1D or 2D image,
the automatic layout transitions apply to the layers corresponding to views
which are used by some subpass in the render pass, even if that subpass does
not reference the given attachment.
If the attachment view is a 2D or 2D array view of a 3D image, even if the
attachment view only refers to a subset of the slices of the selected mip
level of the 3D image, automatic layout transitions apply to the entire
subresource referenced which is the entire mip level in this case.
Automatic layout transitions away from the layout used in a subpass
happen-after the availability operations for all dependencies with that
subpass as the srcSubpass
.
Automatic layout transitions into the layout used in a subpass happen-before
the visibility operations for all dependencies with that subpass as the
dstSubpass
.
Automatic layout transitions away from initialLayout
happen-after the
availability operations for all dependencies with a srcSubpass
equal
to VK_SUBPASS_EXTERNAL
, where dstSubpass
uses the attachment
that will be transitioned.
For attachments created with VK_ATTACHMENT_DESCRIPTION_MAY_ALIAS_BIT
,
automatic layout transitions away from initialLayout
happen-after the
availability operations for all dependencies with a srcSubpass
equal
to VK_SUBPASS_EXTERNAL
, where dstSubpass
uses any aliased
attachment.
Automatic layout transitions into finalLayout
happen-before the
visibility operations for all dependencies with a dstSubpass
equal to
VK_SUBPASS_EXTERNAL
, where srcSubpass
uses the attachment that
will be transitioned.
For attachments created with VK_ATTACHMENT_DESCRIPTION_MAY_ALIAS_BIT
,
automatic layout transitions into finalLayout
happen-before the
visibility operations for all dependencies with a dstSubpass
equal to
VK_SUBPASS_EXTERNAL
, where srcSubpass
uses any aliased
attachment.
The image layout of the depth aspect of a depth/stencil attachment referring
to an image created with
VK_IMAGE_CREATE_SAMPLE_LOCATIONS_COMPATIBLE_DEPTH_BIT_EXT
is dependent
on the last sample locations used to render to the attachment, thus
automatic layout transitions use the sample locations state specified in
VkRenderPassSampleLocationsBeginInfoEXT.
Automatic layout transitions of an attachment referring to a depth/stencil
image created with
VK_IMAGE_CREATE_SAMPLE_LOCATIONS_COMPATIBLE_DEPTH_BIT_EXT
use the
sample locations the image subresource range referenced by the attachment
was last rendered with.
If the current render pass does not use the attachment as a depth/stencil
attachment in any subpass that happens-before, the automatic layout
transition uses the sample locations state specified in the
sampleLocationsInfo
member of the element of the
VkRenderPassSampleLocationsBeginInfoEXT
::pAttachmentInitialSampleLocations
array for which the attachmentIndex
member equals the attachment index
of the attachment, if one is specified.
Otherwise, the automatic layout transition uses the sample locations state
specified in the sampleLocationsInfo
member of the element of the
VkRenderPassSampleLocationsBeginInfoEXT
::pPostSubpassSampleLocations
array for which the subpassIndex
member equals the index of the
subpass that last used the attachment as a depth/stencil attachment, if one
is specified.
If no sample locations state has been specified for an automatic layout
transition performed on an attachment referring to a depth/stencil image
created with VK_IMAGE_CREATE_SAMPLE_LOCATIONS_COMPATIBLE_DEPTH_BIT_EXT
the contents of the depth aspect of the depth/stencil attachment become
undefined as if the layout of the attachment was transitioned from the
VK_IMAGE_LAYOUT_UNDEFINED
layout.
If two subpasses use the same attachment, and both subpasses use the attachment in a read-only layout, no subpass dependency needs to be specified between those subpasses. If an implementation treats those layouts separately, it must insert an implicit subpass dependency between those subpasses to separate the uses in each layout. The subpass dependency operates as if defined with the following parameters:
// Used for input attachments
VkPipelineStageFlags inputAttachmentStages = VK_PIPELINE_STAGE_FRAGMENT_SHADER_BIT;
VkAccessFlags inputAttachmentDstAccess = VK_ACCESS_INPUT_ATTACHMENT_READ_BIT;
// Used for depth/stencil attachments
VkPipelineStageFlags depthStencilAttachmentStages = VK_PIPELINE_STAGE_EARLY_FRAGMENT_TESTS_BIT | VK_PIPELINE_STAGE_LATE_FRAGMENT_TESTS_BIT;
VkAccessFlags depthStencilAttachmentDstAccess = VK_ACCESS_DEPTH_STENCIL_ATTACHMENT_READ_BIT;
VkSubpassDependency implicitDependency = {
.srcSubpass = firstSubpass;
.dstSubpass = secondSubpass;
.srcStageMask = inputAttachmentStages | depthStencilAttachmentStages;
.dstStageMask = inputAttachmentStages | depthStencilAttachmentStages;
.srcAccessMask = 0;
.dstAccessMask = inputAttachmentDstAccess | depthStencilAttachmentDstAccess;
.dependencyFlags = 0;
};
When
drawing using shader objects,
or when
the graphics pipeline is created with
VK_DYNAMIC_STATE_ATTACHMENT_FEEDBACK_LOOP_ENABLE_EXT
set in
VkPipelineDynamicStateCreateInfo::pDynamicStates
, the
application must specify which types of attachments that are written to
during a render pass will also be accessed as non-attachments in the render
pass.
To dynamically set whether a pipeline can access a resource as a non-attachment while it is also used as an attachment that is written to, call:
// Provided by VK_EXT_attachment_feedback_loop_dynamic_state
void vkCmdSetAttachmentFeedbackLoopEnableEXT(
VkCommandBuffer commandBuffer,
VkImageAspectFlags aspectMask);
-
commandBuffer
is the command buffer into which the command will be recorded. -
aspectMask
specifies the types of attachments for which feedback loops will be enabled. Attachment types whose aspects are not included inaspectMask
will have feedback loops disabled.
For attachments that are written to in a render pass, only attachments with
the aspects specified in aspectMask
can be accessed as
non-attachments by subsequent drawing commands.
A more extensible version of render pass creation is also defined below.
To create a render pass, call:
// Provided by VK_VERSION_1_2
VkResult vkCreateRenderPass2(
VkDevice device,
const VkRenderPassCreateInfo2* pCreateInfo,
const VkAllocationCallbacks* pAllocator,
VkRenderPass* pRenderPass);
or the equivalent command
// Provided by VK_KHR_create_renderpass2
VkResult vkCreateRenderPass2KHR(
VkDevice device,
const VkRenderPassCreateInfo2* pCreateInfo,
const VkAllocationCallbacks* pAllocator,
VkRenderPass* pRenderPass);
-
device
is the logical device that creates the render pass. -
pCreateInfo
is a pointer to a VkRenderPassCreateInfo2 structure describing the parameters of the render pass. -
pAllocator
controls host memory allocation as described in the Memory Allocation chapter. -
pRenderPass
is a pointer to a VkRenderPass handle in which the resulting render pass object is returned.
This command is functionally identical to vkCreateRenderPass, but
includes extensible sub-structures that include sType
and pNext
parameters, allowing them to be more easily extended.
The VkRenderPassCreateInfo2
structure is defined as:
// Provided by VK_VERSION_1_2
typedef struct VkRenderPassCreateInfo2 {
VkStructureType sType;
const void* pNext;
VkRenderPassCreateFlags flags;
uint32_t attachmentCount;
const VkAttachmentDescription2* pAttachments;
uint32_t subpassCount;
const VkSubpassDescription2* pSubpasses;
uint32_t dependencyCount;
const VkSubpassDependency2* pDependencies;
uint32_t correlatedViewMaskCount;
const uint32_t* pCorrelatedViewMasks;
} VkRenderPassCreateInfo2;
or the equivalent
// Provided by VK_KHR_create_renderpass2
typedef VkRenderPassCreateInfo2 VkRenderPassCreateInfo2KHR;
-
sType
is a VkStructureType value identifying this structure. -
pNext
isNULL
or a pointer to a structure extending this structure. -
flags
is reserved for future use. -
attachmentCount
is the number of attachments used by this render pass. -
pAttachments
is a pointer to an array ofattachmentCount
VkAttachmentDescription2 structures describing the attachments used by the render pass. -
subpassCount
is the number of subpasses to create. -
pSubpasses
is a pointer to an array ofsubpassCount
VkSubpassDescription2 structures describing each subpass. -
dependencyCount
is the number of dependencies between pairs of subpasses. -
pDependencies
is a pointer to an array ofdependencyCount
VkSubpassDependency2 structures describing dependencies between pairs of subpasses. -
correlatedViewMaskCount
is the number of correlation masks. -
pCorrelatedViewMasks
is a pointer to an array of view masks indicating sets of views that may be more efficient to render concurrently.
Parameters defined by this structure with the same name as those in
VkRenderPassCreateInfo have the identical effect to those parameters;
the child structures are variants of those used in
VkRenderPassCreateInfo which add sType
and pNext
parameters, allowing them to be extended.
If the VkSubpassDescription2::viewMask
member of any element of
pSubpasses
is not zero, multiview functionality is considered to be
enabled for this render pass.
correlatedViewMaskCount
and pCorrelatedViewMasks
have the same
effect as VkRenderPassMultiviewCreateInfo::correlationMaskCount
and VkRenderPassMultiviewCreateInfo::pCorrelationMasks
,
respectively.
The VkAttachmentDescription2
structure is defined as:
// Provided by VK_VERSION_1_2
typedef struct VkAttachmentDescription2 {
VkStructureType sType;
const void* pNext;
VkAttachmentDescriptionFlags flags;
VkFormat format;
VkSampleCountFlagBits samples;
VkAttachmentLoadOp loadOp;
VkAttachmentStoreOp storeOp;
VkAttachmentLoadOp stencilLoadOp;
VkAttachmentStoreOp stencilStoreOp;
VkImageLayout initialLayout;
VkImageLayout finalLayout;
} VkAttachmentDescription2;
or the equivalent
// Provided by VK_KHR_create_renderpass2
typedef VkAttachmentDescription2 VkAttachmentDescription2KHR;
-
sType
is a VkStructureType value identifying this structure. -
pNext
isNULL
or a pointer to a structure extending this structure. -
flags
is a bitmask of VkAttachmentDescriptionFlagBits specifying additional properties of the attachment. -
format
is a VkFormat value specifying the format of the image that will be used for the attachment. -
samples
is a VkSampleCountFlagBits value specifying the number of samples of the image. -
loadOp
is a VkAttachmentLoadOp value specifying how the contents of color and depth components of the attachment are treated at the beginning of the subpass where it is first used. -
storeOp
is a VkAttachmentStoreOp value specifying how the contents of color and depth components of the attachment are treated at the end of the subpass where it is last used. -
stencilLoadOp
is a VkAttachmentLoadOp value specifying how the contents of stencil components of the attachment are treated at the beginning of the subpass where it is first used. -
stencilStoreOp
is a VkAttachmentStoreOp value specifying how the contents of stencil components of the attachment are treated at the end of the last subpass where it is used. -
initialLayout
is the layout the attachment image subresource will be in when a render pass instance begins. -
finalLayout
is the layout the attachment image subresource will be transitioned to when a render pass instance ends.
Parameters defined by this structure with the same name as those in VkAttachmentDescription have the identical effect to those parameters.
If the separateDepthStencilLayouts
feature is enabled, and format
is
a depth/stencil format, initialLayout
and finalLayout
can be
set to a layout that only specifies the layout of the depth aspect.
If the pNext
chain includes a
VkAttachmentDescriptionStencilLayout structure, then the
stencilInitialLayout
and stencilFinalLayout
members specify the
initial and final layouts of the stencil aspect of a depth/stencil format,
and initialLayout
and finalLayout
only apply to the depth
aspect.
For depth-only formats, the VkAttachmentDescriptionStencilLayout
structure is ignored.
For stencil-only formats, the initial and final layouts of the stencil
aspect are taken from the VkAttachmentDescriptionStencilLayout
structure if present, or initialLayout
and finalLayout
if not
present.
If format
is a depth/stencil format, and either initialLayout
or
finalLayout
does not specify a layout for the stencil aspect, then the
application must specify the initial and final layouts of the stencil
aspect by including a VkAttachmentDescriptionStencilLayout structure
in the pNext
chain.
loadOp
and storeOp
are ignored for fragment shading rate
attachments.
No access to the shading rate attachment is performed in loadOp
and
storeOp
.
Instead, access to
VK_ACCESS_FRAGMENT_SHADING_RATE_ATTACHMENT_READ_BIT_KHR
is performed
as fragments are rasterized.
The VkAttachmentDescriptionStencilLayout
structure is defined as:
// Provided by VK_VERSION_1_2
typedef struct VkAttachmentDescriptionStencilLayout {
VkStructureType sType;
void* pNext;
VkImageLayout stencilInitialLayout;
VkImageLayout stencilFinalLayout;
} VkAttachmentDescriptionStencilLayout;
or the equivalent
// Provided by VK_KHR_separate_depth_stencil_layouts
typedef VkAttachmentDescriptionStencilLayout VkAttachmentDescriptionStencilLayoutKHR;
-
sType
is a VkStructureType value identifying this structure. -
pNext
isNULL
or a pointer to a structure extending this structure. -
stencilInitialLayout
is the layout the stencil aspect of the attachment image subresource will be in when a render pass instance begins. -
stencilFinalLayout
is the layout the stencil aspect of the attachment image subresource will be transitioned to when a render pass instance ends.
The VkSubpassDescription2
structure is defined as:
// Provided by VK_VERSION_1_2
typedef struct VkSubpassDescription2 {
VkStructureType sType;
const void* pNext;
VkSubpassDescriptionFlags flags;
VkPipelineBindPoint pipelineBindPoint;
uint32_t viewMask;
uint32_t inputAttachmentCount;
const VkAttachmentReference2* pInputAttachments;
uint32_t colorAttachmentCount;
const VkAttachmentReference2* pColorAttachments;
const VkAttachmentReference2* pResolveAttachments;
const VkAttachmentReference2* pDepthStencilAttachment;
uint32_t preserveAttachmentCount;
const uint32_t* pPreserveAttachments;
} VkSubpassDescription2;
or the equivalent
// Provided by VK_KHR_create_renderpass2
typedef VkSubpassDescription2 VkSubpassDescription2KHR;
-
sType
is a VkStructureType value identifying this structure. -
pNext
isNULL
or a pointer to a structure extending this structure. -
flags
is a bitmask of VkSubpassDescriptionFlagBits specifying usage of the subpass. -
pipelineBindPoint
is a VkPipelineBindPoint value specifying the pipeline type supported for this subpass. -
viewMask
is a bitfield of view indices describing which views rendering is broadcast to in this subpass, when multiview is enabled. -
inputAttachmentCount
is the number of input attachments. -
pInputAttachments
is a pointer to an array of VkAttachmentReference2 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 ofcolorAttachmentCount
VkAttachmentReference2 structures defining the color attachments for this subpass and their layouts. -
pResolveAttachments
isNULL
or a pointer to an array ofcolorAttachmentCount
VkAttachmentReference2 structures defining the resolve attachments for this subpass and their layouts. -
pDepthStencilAttachment
is a pointer to a VkAttachmentReference2 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 ofpreserveAttachmentCount
render pass attachment indices identifying attachments that are not used by this subpass, but whose contents must be preserved throughout the subpass.
Parameters defined by this structure with the same name as those in VkSubpassDescription have the identical effect to those parameters.
viewMask
has the same effect for the described subpass as
VkRenderPassMultiviewCreateInfo::pViewMasks
has on each
corresponding subpass.
If a VkFragmentShadingRateAttachmentInfoKHR structure is included in
the pNext
chain, pFragmentShadingRateAttachment
is not NULL
,
and its attachment
member is not VK_ATTACHMENT_UNUSED
, the
identified attachment defines a fragment shading rate attachment for that
subpass.
If any element of pResolveAttachments
is an image specified with an
VkExternalFormatANDROID, values in the corresponding color attachment
will be resolved to the resolve attachment in the same manner as specified
for VK_RESOLVE_MODE_EXTERNAL_FORMAT_DOWNSAMPLE_ANDROID
.
If the nullColorAttachmentWithExternalFormatResolve
limit is VK_TRUE
,
values in the color attachment will be loaded from the resolve attachment at
the start of rendering, and may also be reloaded any time after a resolve
occurs or the resolve attachment is written to; if this occurs it must
happen-before any writes to the color attachment are performed which
happen-after the resolve that triggers this.
If any color component in the external format is subsampled, values will be
read from the nearest sample in the image when they are loaded.
If the color attachment is also used as an input attachment, the same
behavior applies.
Setting the color attachment to VK_ATTACHMENT_UNUSED
when an external
resolve attachment is used and the
nullColorAttachmentWithExternalFormatResolve
limit is VK_TRUE
will not result in color attachment writes to be discarded for that
attachment.
When nullColorAttachmentWithExternalFormatResolve
is VK_TRUE
, the
color output from the subpass can still be read via an input attachment; but
the application cannot bind an image view for the color attachment as there
is no such image view bound.
Instead to access the data as an input attachment applications can use the
resolve attachment in its place - using the resolve attachment image for the
descriptor, and setting the corresponding element of pInputAttachments
to the index of the resolve attachment.
Loads or input attachment reads from the resolve attachment are performed as if using a VkSamplerYcbcrConversionCreateInfo with the following parameters:
VkSamplerYcbcrConversionCreateInfo createInfo = {
.sType = VK_STRUCTURE_TYPE_SAMPLER_YCBCR_CONVERSION_CREATE_INFO,
.pNext = NULL,
.format = VK_FORMAT_UNDEFINED,
.ycbcrModel = VK_SAMPLER_YCBCR_MODEL_CONVERSION_RGB_IDENTITY,
.ycbcrRange = VK_SAMPLER_YCBCR_RANGE_ITU_FULL,
.components = {
.r = VK_COMPONENT_SWIZZLE_B
.g = VK_COMPONENT_SWIZZLE_R
.b = VK_COMPONENT_SWIZZLE_G
.a = VK_COMPONENT_SWIZZLE_IDENTITY},
.xChromaOffset = properties.chromaOffsetX,
.yChromaOffset = properties.chromaOffsetY,
.chromaFilter = VK_FILTER_NEAREST,
.forceExplicitReconstruction = ... };
where properties
is equal to
VkPhysicalDeviceExternalFormatResolvePropertiesANDROID returned by the
device and forceExplicitReconstruction
is effectively ignored as the
VK_SAMPLER_YCBCR_MODEL_CONVERSION_RGB_IDENTITY
model is used.
The applied swizzle is the same effective swizzle that would be applied by
the VK_SAMPLER_YCBCR_MODEL_CONVERSION_YCBCR_IDENTITY
model, but no
range expansion is applied.
The VkSubpassDescriptionDepthStencilResolve
structure is defined as:
// Provided by VK_VERSION_1_2
typedef struct VkSubpassDescriptionDepthStencilResolve {
VkStructureType sType;
const void* pNext;
VkResolveModeFlagBits depthResolveMode;
VkResolveModeFlagBits stencilResolveMode;
const VkAttachmentReference2* pDepthStencilResolveAttachment;
} VkSubpassDescriptionDepthStencilResolve;
or the equivalent
// Provided by VK_KHR_depth_stencil_resolve
typedef VkSubpassDescriptionDepthStencilResolve VkSubpassDescriptionDepthStencilResolveKHR;
-
sType
is a VkStructureType value identifying this structure. -
pNext
isNULL
or a pointer to a structure extending this structure. -
depthResolveMode
is a VkResolveModeFlagBits value describing the depth resolve mode. -
stencilResolveMode
is a VkResolveModeFlagBits value describing the stencil resolve mode. -
pDepthStencilResolveAttachment
isNULL
or a pointer to a VkAttachmentReference2 structure defining the depth/stencil resolve attachment for this subpass and its layout.
If the pNext
chain of VkSubpassDescription2 includes a
VkSubpassDescriptionDepthStencilResolve
structure, then that structure
describes multisample resolve operations
for the depth/stencil attachment in a subpass.
If this structure is not included in the pNext
chain of
VkSubpassDescription2, or if it is and either
pDepthStencilResolveAttachment
is NULL
or its attachment index is
VK_ATTACHMENT_UNUSED
, it indicates that no depth/stencil resolve
attachment will be used in the subpass.
The VkFragmentShadingRateAttachmentInfoKHR
structure is defined as:
// Provided by VK_KHR_fragment_shading_rate
typedef struct VkFragmentShadingRateAttachmentInfoKHR {
VkStructureType sType;
const void* pNext;
const VkAttachmentReference2* pFragmentShadingRateAttachment;
VkExtent2D shadingRateAttachmentTexelSize;
} VkFragmentShadingRateAttachmentInfoKHR;
-
sType
is a VkStructureType value identifying this structure. -
pNext
isNULL
or a pointer to a structure extending this structure. -
pFragmentShadingRateAttachment
isNULL
or a pointer to a VkAttachmentReference2 structure defining the fragment shading rate attachment for this subpass. -
shadingRateAttachmentTexelSize
specifies the size of the portion of the framebuffer corresponding to each texel inpFragmentShadingRateAttachment
.
If no shading rate attachment is specified, or if this structure is not specified, the implementation behaves as if a valid shading rate attachment was specified with all texels specifying a single pixel per fragment.
If the pNext
chain of VkSubpassDescription2
or VkRenderingInfo
includes a VkMultisampledRenderToSingleSampledInfoEXT
structure, then
that structure describes how multisampled rendering is performed on single
sampled attachments in that subpass.
The VkMultisampledRenderToSingleSampledInfoEXT
structure is defined
as:
// Provided by VK_EXT_multisampled_render_to_single_sampled
typedef struct VkMultisampledRenderToSingleSampledInfoEXT {
VkStructureType sType;
const void* pNext;
VkBool32 multisampledRenderToSingleSampledEnable;
VkSampleCountFlagBits rasterizationSamples;
} VkMultisampledRenderToSingleSampledInfoEXT;
-
sType
is a VkStructureType value identifying this structure. -
pNext
isNULL
or a pointer to a structure extending this structure. -
multisampledRenderToSingleSampledEnable
controls whether multisampled rendering to single-sampled attachments is performed as described below. -
rasterizationSamples
is a VkSampleCountFlagBits specifying the number of samples used in rasterization.
If the pNext
chain of VkSubpassDescription2
or VkRenderingInfo
includes a VkMultisampledRenderToSingleSampledInfoEXT structure whose
multisampledRenderToSingleSampledEnable
field is VK_TRUE
, the
graphics pipelines must have
VkGraphicsPipelineCreateInfo::rasterizationSamples
equal to
VkMultisampledRenderToSingleSampledInfoEXT::rasterizationSamples
,
and the subpass attachments can have a sample count of
VK_SAMPLE_COUNT_1_BIT
.
For attachments with a sample count of VK_SAMPLE_COUNT_1_BIT
,
multisampled rendering is performed to an intermediate multisampled image
with
VkMultisampledRenderToSingleSampledInfoEXT::rasterizationSamples
samples, implicitly allocated by the implementation for the duration of the
subpass.
For such attachments:
-
If
loadOp
equals toVK_ATTACHMENT_LOAD_OP_LOAD
, samples of the implicit image are initialized by replicating the value from the corresponding pixel in the attachment. -
If
storeOp
orstencilStoreOp
is equal toVK_ATTACHMENT_STORE_OP_STORE
, the implicit image is implicitly resolved prior to storage in the attachment.
Memory constraints due to high primitive counts may result in an implicit
split of the subpass.
This is the equivalent of partial rasterization of geometry in a render pass
that ends in storeOp
and stencilStoreOp
equal to
VK_ATTACHMENT_STORE_OP_STORE
, followed by another render pass with
loadOp
and stencilLoadOp
equal to
VK_ATTACHMENT_LOAD_OP_LOAD
with appropriate barriers in between.
When VkMultisampledRenderToSingleSampledInfoEXT is used, the
implementation is allowed to resolve attachments with a sample count of
VK_SAMPLE_COUNT_1_BIT
and lose multisampled data on such splits.
The implementation may similarly split the render pass at subpass
boundaries even if they use the same value for
VkMultisampledRenderToSingleSampledInfoEXT::rasterizationSamples
.
The VkAttachmentReference2
structure is defined as:
// Provided by VK_VERSION_1_2
typedef struct VkAttachmentReference2 {
VkStructureType sType;
const void* pNext;
uint32_t attachment;
VkImageLayout layout;
VkImageAspectFlags aspectMask;
} VkAttachmentReference2;
or the equivalent
// Provided by VK_KHR_create_renderpass2
typedef VkAttachmentReference2 VkAttachmentReference2KHR;
-
sType
is a VkStructureType value identifying this structure. -
pNext
isNULL
or a pointer to a structure extending this structure. -
attachment
is either an integer value identifying an attachment at the corresponding index in VkRenderPassCreateInfo2::pAttachments
, orVK_ATTACHMENT_UNUSED
to signify that this attachment is not used. -
layout
is a VkImageLayout value specifying the layout the attachment uses during the subpass. -
aspectMask
is a mask of which aspect(s) can be accessed within the specified subpass as an input attachment.
Parameters defined by this structure with the same name as those in VkAttachmentReference have the identical effect to those parameters.
aspectMask
is ignored when this structure is used to describe anything
other than an input attachment reference.
If the separateDepthStencilLayouts
feature is enabled, and attachment
has a depth/stencil format, layout
can be set to a layout that only
specifies the layout of the depth aspect.
If layout
only specifies the layout of the depth aspect of the
attachment, the layout of the stencil aspect is specified by the
stencilLayout
member of a VkAttachmentReferenceStencilLayout
structure included in the pNext
chain.
Otherwise, layout
describes the layout for all relevant image aspects.
The VkAttachmentReferenceStencilLayout
structure is defined as:
// Provided by VK_VERSION_1_2
typedef struct VkAttachmentReferenceStencilLayout {
VkStructureType sType;
void* pNext;
VkImageLayout stencilLayout;
} VkAttachmentReferenceStencilLayout;
or the equivalent
// Provided by VK_KHR_separate_depth_stencil_layouts
typedef VkAttachmentReferenceStencilLayout VkAttachmentReferenceStencilLayoutKHR;
-
sType
is a VkStructureType value identifying this structure. -
pNext
isNULL
or a pointer to a structure extending this structure. -
stencilLayout
is a VkImageLayout value specifying the layout the stencil aspect of the attachment uses during the subpass.
The VkSubpassDependency2
structure is defined as:
// Provided by VK_VERSION_1_2
typedef struct VkSubpassDependency2 {
VkStructureType sType;
const void* pNext;
uint32_t srcSubpass;
uint32_t dstSubpass;
VkPipelineStageFlags srcStageMask;
VkPipelineStageFlags dstStageMask;
VkAccessFlags srcAccessMask;
VkAccessFlags dstAccessMask;
VkDependencyFlags dependencyFlags;
int32_t viewOffset;
} VkSubpassDependency2;
or the equivalent
// Provided by VK_KHR_create_renderpass2
typedef VkSubpassDependency2 VkSubpassDependency2KHR;
-
sType
is a VkStructureType value identifying this structure. -
pNext
isNULL
or a pointer to a structure extending this structure. -
srcSubpass
is the subpass index of the first subpass in the dependency, orVK_SUBPASS_EXTERNAL
. -
dstSubpass
is the subpass index of the second subpass in the dependency, orVK_SUBPASS_EXTERNAL
. -
srcStageMask
is a bitmask of VkPipelineStageFlagBits specifying the source stage mask. -
dstStageMask
is a bitmask of VkPipelineStageFlagBits specifying the destination stage mask -
srcAccessMask
is a bitmask of VkAccessFlagBits specifying a source access mask. -
dstAccessMask
is a bitmask of VkAccessFlagBits specifying a destination access mask. -
dependencyFlags
is a bitmask of VkDependencyFlagBits. -
viewOffset
controls which views in the source subpass the views in the destination subpass depend on.
Parameters defined by this structure with the same name as those in VkSubpassDependency have the identical effect to those parameters.
viewOffset
has the same effect for the described subpass dependency as
VkRenderPassMultiviewCreateInfo::pViewOffsets
has on each
corresponding subpass dependency.
If a VkMemoryBarrier2 is included in the pNext
chain,
srcStageMask
, dstStageMask
, srcAccessMask
, and
dstAccessMask
parameters are ignored.
The synchronization and access scopes instead are defined by the parameters
of VkMemoryBarrier2.
To destroy a render pass, call:
// Provided by VK_VERSION_1_0
void vkDestroyRenderPass(
VkDevice device,
VkRenderPass renderPass,
const VkAllocationCallbacks* pAllocator);
-
device
is the logical device that destroys the render pass. -
renderPass
is the handle of the render pass to destroy. -
pAllocator
controls host memory allocation as described in the Memory Allocation chapter.
Render Pass Compatibility
Framebuffers and graphics pipelines are created based on a specific render pass object. They must only be used with that render pass object, or one compatible with it.
Two attachment references are compatible if they have matching format and
sample count, or are both VK_ATTACHMENT_UNUSED
or the pointer that
would contain the reference is NULL
.
Two arrays of attachment references are compatible if all corresponding
pairs of attachments are compatible.
If the arrays are of different lengths, attachment references not present in
the smaller array are treated as VK_ATTACHMENT_UNUSED
.
Two render passes are compatible if their corresponding color, input, resolve, and depth/stencil attachment references are compatible and if they are otherwise identical except for:
-
Initial and final image layout in attachment descriptions
-
Load and store operations in attachment descriptions
-
Image layout in attachment references
As an additional special case, if two render passes have a single subpass, the resolve attachment reference and depth/stencil resolve mode compatibility requirements are ignored.
A framebuffer is compatible with a render pass if it was created using the same render pass or a compatible render pass.
Framebuffers
Render passes operate in conjunction with framebuffers. Framebuffers represent a collection of specific memory attachments that a render pass instance uses.
Framebuffers are represented by VkFramebuffer
handles:
// Provided by VK_VERSION_1_0
VK_DEFINE_NON_DISPATCHABLE_HANDLE(VkFramebuffer)
To create a framebuffer, call:
// Provided by VK_VERSION_1_0
VkResult vkCreateFramebuffer(
VkDevice device,
const VkFramebufferCreateInfo* pCreateInfo,
const VkAllocationCallbacks* pAllocator,
VkFramebuffer* pFramebuffer);
-
device
is the logical device that creates the framebuffer. -
pCreateInfo
is a pointer to a VkFramebufferCreateInfo structure describing additional information about framebuffer creation. -
pAllocator
controls host memory allocation as described in the Memory Allocation chapter. -
pFramebuffer
is a pointer to a VkFramebuffer handle in which the resulting framebuffer object is returned.
The VkFramebufferCreateInfo
structure is defined as:
// Provided by VK_VERSION_1_0
typedef struct VkFramebufferCreateInfo {
VkStructureType sType;
const void* pNext;
VkFramebufferCreateFlags flags;
VkRenderPass renderPass;
uint32_t attachmentCount;
const VkImageView* pAttachments;
uint32_t width;
uint32_t height;
uint32_t layers;
} VkFramebufferCreateInfo;
-
sType
is a VkStructureType value identifying this structure. -
pNext
isNULL
or a pointer to a structure extending this structure. -
flags
is a bitmask of VkFramebufferCreateFlagBits -
renderPass
is a render pass defining what render passes the framebuffer will be compatible with. See Render Pass Compatibility for details. -
attachmentCount
is the number of attachments. -
pAttachments
is a pointer to an array of VkImageView handles, each of which will be used as the corresponding attachment in a render pass instance. Ifflags
includesVK_FRAMEBUFFER_CREATE_IMAGELESS_BIT
, this parameter is ignored. -
width
,height
andlayers
define the dimensions of the framebuffer. If the render pass uses multiview, thenlayers
must be one and each attachment requires a number of layers that is greater than the maximum bit index set in the view mask in the subpasses in which it is used.
It is legal for a subpass to use no color or depth/stencil attachments,
either because it has no attachment references or because all of them are
VK_ATTACHMENT_UNUSED
.
This kind of subpass can use shader side effects such as image stores and
atomics to produce an output.
In this case, the subpass continues to use the width
, height
,
and layers
of the framebuffer to define the dimensions of the
rendering area, and the rasterizationSamples
from each pipeline’s
VkPipelineMultisampleStateCreateInfo to define the number of samples
used in rasterization; however, if
VkPhysicalDeviceFeatures::variableMultisampleRate
is
VK_FALSE
, then all pipelines to be bound with the subpass must have
the same value for
VkPipelineMultisampleStateCreateInfo::rasterizationSamples
.
In all such cases, rasterizationSamples
must be a valid
VkSampleCountFlagBits value that is set in
VkPhysicalDeviceLimits::framebufferNoAttachmentsSampleCounts
.
The VkFramebufferAttachmentsCreateInfo
structure is defined as:
// Provided by VK_VERSION_1_2
typedef struct VkFramebufferAttachmentsCreateInfo {
VkStructureType sType;
const void* pNext;
uint32_t attachmentImageInfoCount;
const VkFramebufferAttachmentImageInfo* pAttachmentImageInfos;
} VkFramebufferAttachmentsCreateInfo;
or the equivalent
// Provided by VK_KHR_imageless_framebuffer
typedef VkFramebufferAttachmentsCreateInfo VkFramebufferAttachmentsCreateInfoKHR;
-
sType
is a VkStructureType value identifying this structure. -
pNext
isNULL
or a pointer to a structure extending this structure. -
attachmentImageInfoCount
is the number of attachments being described. -
pAttachmentImageInfos
is a pointer to an array of VkFramebufferAttachmentImageInfo structures, each structure describing a number of parameters of the corresponding attachment in a render pass instance.
The VkFramebufferAttachmentImageInfo
structure is defined as:
// Provided by VK_VERSION_1_2
typedef struct VkFramebufferAttachmentImageInfo {
VkStructureType sType;
const void* pNext;
VkImageCreateFlags flags;
VkImageUsageFlags usage;
uint32_t width;
uint32_t height;
uint32_t layerCount;
uint32_t viewFormatCount;
const VkFormat* pViewFormats;
} VkFramebufferAttachmentImageInfo;
or the equivalent
// Provided by VK_KHR_imageless_framebuffer
typedef VkFramebufferAttachmentImageInfo VkFramebufferAttachmentImageInfoKHR;
-
sType
is a VkStructureType value identifying this structure. -
pNext
isNULL
or a pointer to a structure extending this structure. -
flags
is a bitmask of VkImageCreateFlagBits, matching the value of VkImageCreateInfo::flags
used to create an image that will be used with this framebuffer. -
usage
is a bitmask of VkImageUsageFlagBits, matching the value of VkImageCreateInfo::usage
used to create an image used with this framebuffer. -
width
is the width of the image view used for rendering. -
height
is the height of the image view used for rendering. -
layerCount
is the number of array layers of the image view used for rendering. -
viewFormatCount
is the number of entries in thepViewFormats
array, matching the value of VkImageFormatListCreateInfo::viewFormatCount
used to create an image used with this framebuffer. -
pViewFormats
is a pointer to an array of VkFormat values specifying all of the formats which can be used when creating views of the image, matching the value of VkImageFormatListCreateInfo::pViewFormats
used to create an image used with this framebuffer.
Images that can be used with the framebuffer when beginning a render pass, as specified by VkRenderPassAttachmentBeginInfo, must be created with parameters that are identical to those specified here.
Bits which can be set in VkFramebufferCreateInfo::flags
,
specifying options for framebuffers, are:
// Provided by VK_VERSION_1_0
typedef enum VkFramebufferCreateFlagBits {
// Provided by VK_VERSION_1_2
VK_FRAMEBUFFER_CREATE_IMAGELESS_BIT = 0x00000001,
// Provided by VK_KHR_imageless_framebuffer
VK_FRAMEBUFFER_CREATE_IMAGELESS_BIT_KHR = VK_FRAMEBUFFER_CREATE_IMAGELESS_BIT,
} VkFramebufferCreateFlagBits;
-
VK_FRAMEBUFFER_CREATE_IMAGELESS_BIT
specifies that image views are not specified, and only attachment compatibility information will be provided via a VkFramebufferAttachmentImageInfo structure.
// Provided by VK_VERSION_1_0
typedef VkFlags VkFramebufferCreateFlags;
VkFramebufferCreateFlags
is a bitmask type for setting a mask of zero
or more VkFramebufferCreateFlagBits.
To destroy a framebuffer, call:
// Provided by VK_VERSION_1_0
void vkDestroyFramebuffer(
VkDevice device,
VkFramebuffer framebuffer,
const VkAllocationCallbacks* pAllocator);
-
device
is the logical device that destroys the framebuffer. -
framebuffer
is the handle of the framebuffer to destroy. -
pAllocator
controls host memory allocation as described in the Memory Allocation chapter.
Render Pass Load Operations
Render pass load operations define the initial values of an attachment during a render pass instance.
Load operations for attachments with a depth/stencil format execute in the
VK_PIPELINE_STAGE_EARLY_FRAGMENT_TESTS_BIT
pipeline stage.
Load operations for attachments with a color format execute in the
VK_PIPELINE_STAGE_COLOR_ATTACHMENT_OUTPUT_BIT
pipeline stage.
The load operation for each sample in an attachment happens-before any
recorded command which accesses the sample in that render pass instance via
that attachment or an alias.
Because load operations always happen first, external synchronization with
attachment access only needs to synchronize the load operations with
previous commands; not the operations within the render pass instance.
This does not apply when using |
Load operations only update values within the defined render area for the
render pass instance.
However, any writes performed by a load operation (as defined by its access
masks) to a given attachment may read and write back any memory locations
within the image subresource bound for that attachment.
For depth/stencil images,
if maintenance7 is not enabled on the device or
separateDepthStencilAttachmentAccess
is VK_FALSE
,
writes to one aspect may also result in read-modify-write operations for
the other aspect.
If the subresource is in the
VK_IMAGE_LAYOUT_ATTACHMENT_FEEDBACK_LOOP_OPTIMAL_EXT
layout,
implementations must not access pixels outside of the render area.
As entire subresources could be accessed by load operations, applications cannot safely access values outside of the render area during a render pass instance when a load operation that modifies values is used. |
Load operations that can be used for a render pass are:
// Provided by VK_VERSION_1_0
typedef enum VkAttachmentLoadOp {
VK_ATTACHMENT_LOAD_OP_LOAD = 0,
VK_ATTACHMENT_LOAD_OP_CLEAR = 1,
VK_ATTACHMENT_LOAD_OP_DONT_CARE = 2,
// Provided by VK_KHR_load_store_op_none
VK_ATTACHMENT_LOAD_OP_NONE_KHR = 1000400000,
// Provided by VK_EXT_load_store_op_none
VK_ATTACHMENT_LOAD_OP_NONE_EXT = VK_ATTACHMENT_LOAD_OP_NONE_KHR,
} VkAttachmentLoadOp;
-
VK_ATTACHMENT_LOAD_OP_LOAD
specifies that the previous contents of the image within the render area will be preserved as the initial values. For attachments with a depth/stencil format, this uses the access typeVK_ACCESS_DEPTH_STENCIL_ATTACHMENT_READ_BIT
. For attachments with a color format, this uses the access typeVK_ACCESS_COLOR_ATTACHMENT_READ_BIT
. -
VK_ATTACHMENT_LOAD_OP_CLEAR
specifies that the contents within the render area will be cleared to a uniform value, which is specified when a render pass instance is begun. For attachments with a depth/stencil format, this uses the access typeVK_ACCESS_DEPTH_STENCIL_ATTACHMENT_WRITE_BIT
. For attachments with a color format, this uses the access typeVK_ACCESS_COLOR_ATTACHMENT_WRITE_BIT
. -
VK_ATTACHMENT_LOAD_OP_DONT_CARE
specifies that the previous contents within the area need not be preserved; the contents of the attachment will be undefined inside the render area. For attachments with a depth/stencil format, this uses the access typeVK_ACCESS_DEPTH_STENCIL_ATTACHMENT_WRITE_BIT
. For attachments with a color format, this uses the access typeVK_ACCESS_COLOR_ATTACHMENT_WRITE_BIT
. -
VK_ATTACHMENT_LOAD_OP_NONE_KHR
specifies that the previous contents of the image will be undefined inside the render pass. No access type is used as the image is not accessed.
During a render pass instance, input and color attachments with color
formats that have a component size of 8, 16, or 32 bits must be represented
in the attachment’s format throughout the instance.
Attachments with other floating- or fixed-point color formats, or with depth
components may be represented in a format with a precision higher than the
attachment format, but must be represented with the same range.
When such a component is loaded via the loadOp
, it will be converted
into an implementation-dependent format used by the render pass.
Such components must be converted from the render pass format, to the
format of the attachment, before they are resolved or stored at the end of a
render pass instance via storeOp
.
Conversions occur as described in Numeric Representation and Computation and Fixed-Point Data Conversions.
Render Pass Store Operations
Render pass store operations define how values written to an attachment during a render pass instance are stored to memory.
Store operations for attachments with a depth/stencil format execute in the
VK_PIPELINE_STAGE_LATE_FRAGMENT_TESTS_BIT
pipeline stage.
Store operations for attachments with a color format execute in the
VK_PIPELINE_STAGE_COLOR_ATTACHMENT_OUTPUT_BIT
pipeline stage.
The store operation for each sample in an attachment happens-after any
recorded command which accesses the sample via that attachment or an alias.
Because store operations always happen after other accesses in a render pass
instance, external synchronization with attachment access in an earlier
render pass only needs to synchronize with the store operations; not the
operations within the render pass instance.
This does not apply when using |
Store operations only update values within the defined render area for the
render pass instance.
However, any writes performed by a store operation (as defined by its access
masks) to a given attachment may read and write back any memory locations
within the image subresource bound for that attachment.
For depth/stencil images,
if
separateDepthStencilAttachmentAccess
is VK_FALSE
,
writes to one aspect may also result in read-modify-write operations for
the other aspect.
If the subresource is in the
VK_IMAGE_LAYOUT_ATTACHMENT_FEEDBACK_LOOP_OPTIMAL_EXT
layout,
implementations must not access pixels outside of the render area.
As entire subresources could be accessed by store operations, applications cannot safely access values outside of the render area via aliased resources during a render pass instance when a store operation that modifies values is used. |
Possible values of VkAttachmentDescription::storeOp
and
stencilStoreOp
, specifying how the contents of the attachment are
treated, are:
// Provided by VK_VERSION_1_0
typedef enum VkAttachmentStoreOp {
VK_ATTACHMENT_STORE_OP_STORE = 0,
VK_ATTACHMENT_STORE_OP_DONT_CARE = 1,
// Provided by VK_VERSION_1_3
VK_ATTACHMENT_STORE_OP_NONE = 1000301000,
// Provided by VK_KHR_dynamic_rendering, VK_KHR_load_store_op_none
VK_ATTACHMENT_STORE_OP_NONE_KHR = VK_ATTACHMENT_STORE_OP_NONE,
// Provided by VK_QCOM_render_pass_store_ops
VK_ATTACHMENT_STORE_OP_NONE_QCOM = VK_ATTACHMENT_STORE_OP_NONE,
// Provided by VK_EXT_load_store_op_none
VK_ATTACHMENT_STORE_OP_NONE_EXT = VK_ATTACHMENT_STORE_OP_NONE,
} VkAttachmentStoreOp;
-
VK_ATTACHMENT_STORE_OP_STORE
specifies the contents generated during the render pass and within the render area are written to memory. For attachments with a depth/stencil format, this uses the access typeVK_ACCESS_DEPTH_STENCIL_ATTACHMENT_WRITE_BIT
. For attachments with a color format, this uses the access typeVK_ACCESS_COLOR_ATTACHMENT_WRITE_BIT
. -
VK_ATTACHMENT_STORE_OP_DONT_CARE
specifies the contents within the render area are not needed after rendering, and may be discarded; the contents of the attachment will be undefined inside the render area. For attachments with a depth/stencil format, this uses the access typeVK_ACCESS_DEPTH_STENCIL_ATTACHMENT_WRITE_BIT
. For attachments with a color format, this uses the access typeVK_ACCESS_COLOR_ATTACHMENT_WRITE_BIT
. -
VK_ATTACHMENT_STORE_OP_NONE
specifies the contents within the render area are not accessed by the store operation as long as no values are written to the attachment during the render pass. If values are written during the render pass, this behaves identically toVK_ATTACHMENT_STORE_OP_DONT_CARE
and with matching access semantics.
|
Render Pass Multisample Resolve Operations
Render pass multisample resolve operations combine sample values from a single pixel in a multisample attachment and store the result to the corresponding pixel in a single sample attachment.
Multisample resolve operations for attachments execute in the
VK_PIPELINE_STAGE_COLOR_ATTACHMENT_OUTPUT_BIT
pipeline stage.
A final resolve operation for all pixels in the render area happens-after
any recorded command which writes a pixel via the multisample attachment to
be resolved or an explicit alias of it in the subpass that it is specified.
Any single sample attachment specified for use in a multisample resolve
operation may have its contents modified at any point once rendering begins
for the render pass instance.
Reads from the multisample attachment can be synchronized with
VK_ACCESS_COLOR_ATTACHMENT_READ_BIT
.
Access to the single sample attachment can be synchronized with
VK_ACCESS_COLOR_ATTACHMENT_READ_BIT
and
VK_ACCESS_COLOR_ATTACHMENT_WRITE_BIT
.
These pipeline stage and access types are used whether the attachments are
color or depth/stencil attachments.
When using render pass objects, a subpass dependency specified with the above pipeline stages and access flags will ensure synchronization with multisample resolve operations for any attachments that were last accessed by that subpass. This allows later subpasses to read resolved values as input attachments.
Resolve operations only update values within the defined render area for the
render pass instance.
However, any writes performed by a resolve operation (as defined by its
access masks) to a given attachment may read and write back any memory
locations within the image subresource bound for that attachment.
For depth/stencil images,
if
separateDepthStencilAttachmentAccess
is VK_FALSE
,
writes to one aspect may also result in read-modify-write operations for
the other aspect.
If the subresource is in the
VK_IMAGE_LAYOUT_ATTACHMENT_FEEDBACK_LOOP_OPTIMAL_EXT
layout,
implementations must not access pixels outside of the render area.
As entire subresources could be accessed by multisample resolve operations, applications cannot safely access values outside of the render area via aliased resources during a render pass instance when a multisample resolve operation is performed. |
Multisample values in a multisample attachment are combined according to the resolve mode used:
// Provided by VK_VERSION_1_2
typedef enum VkResolveModeFlagBits {
VK_RESOLVE_MODE_NONE = 0,
VK_RESOLVE_MODE_SAMPLE_ZERO_BIT = 0x00000001,
VK_RESOLVE_MODE_AVERAGE_BIT = 0x00000002,
VK_RESOLVE_MODE_MIN_BIT = 0x00000004,
VK_RESOLVE_MODE_MAX_BIT = 0x00000008,
// Provided by VK_ANDROID_external_format_resolve with VK_KHR_dynamic_rendering or VK_VERSION_1_3
VK_RESOLVE_MODE_EXTERNAL_FORMAT_DOWNSAMPLE_ANDROID = 0x00000010,
// Provided by VK_KHR_depth_stencil_resolve
VK_RESOLVE_MODE_NONE_KHR = VK_RESOLVE_MODE_NONE,
// Provided by VK_KHR_depth_stencil_resolve
VK_RESOLVE_MODE_SAMPLE_ZERO_BIT_KHR = VK_RESOLVE_MODE_SAMPLE_ZERO_BIT,
// Provided by VK_KHR_depth_stencil_resolve
VK_RESOLVE_MODE_AVERAGE_BIT_KHR = VK_RESOLVE_MODE_AVERAGE_BIT,
// Provided by VK_KHR_depth_stencil_resolve
VK_RESOLVE_MODE_MIN_BIT_KHR = VK_RESOLVE_MODE_MIN_BIT,
// Provided by VK_KHR_depth_stencil_resolve
VK_RESOLVE_MODE_MAX_BIT_KHR = VK_RESOLVE_MODE_MAX_BIT,
} VkResolveModeFlagBits;
or the equivalent
// Provided by VK_KHR_depth_stencil_resolve
typedef VkResolveModeFlagBits VkResolveModeFlagBitsKHR;
-
VK_RESOLVE_MODE_NONE
indicates that no resolve operation is done. -
VK_RESOLVE_MODE_SAMPLE_ZERO_BIT
indicates that result of the resolve operation is equal to the value of sample 0. -
VK_RESOLVE_MODE_AVERAGE_BIT
indicates that result of the resolve operation is the average of the sample values. -
VK_RESOLVE_MODE_MIN_BIT
indicates that result of the resolve operation is the minimum of the sample values. -
VK_RESOLVE_MODE_MAX_BIT
indicates that result of the resolve operation is the maximum of the sample values. -
VK_RESOLVE_MODE_EXTERNAL_FORMAT_DOWNSAMPLE_ANDROID
indicates that rather than a multisample resolve, a single sampled color attachment will be downsampled into a Y′CBCR format image specified by an external Android format. Unlike other resolve modes, implementations can resolve multiple times during rendering, or even bypass writing to the color attachment altogether, as long as the final value is resolved to the resolve attachment. Values in the G, B, and R channels of the color attachment will be written to the Y, CB, and CR channels of the external format image, respectively. Chroma values are calculated as if sampling with a linear filter from the color attachment at full rate, at the location the chroma values sit according to VkPhysicalDeviceExternalFormatResolvePropertiesANDROID::chromaOffsetX
, VkPhysicalDeviceExternalFormatResolvePropertiesANDROID::chromaOffsetY
, and the chroma sample rate of the resolved image.
If no resolve mode is otherwise specified, VK_RESOLVE_MODE_AVERAGE_BIT
is used.
No range compression or Y′CBCR model conversion is performed by
|