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Algorithm steps for attachment load/store (gpuweb#4706)
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* Algorithm steps for attachment load/store

* Address Kai's feedback
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@toji
toji authored Jun 13, 2024
1 parent 0e9ee00 commit 538a4c7
Showing 1 changed file with 140 additions and 4 deletions.
144 changes: 140 additions & 4 deletions spec/index.bs
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Original file line number Diff line number Diff line change
Expand Up @@ -9598,6 +9598,7 @@ dictionary GPUCommandEncoderDescriptor
</div>
1. Set |pass|.{{GPURenderCommandsMixin/[[drawCount]]}} to 0.
1. Set |pass|.{{GPURenderPassEncoder/[[maxDrawCount]]}} to |descriptor|.{{GPURenderPassDescriptor/maxDrawCount}}.
1. Set |pass|.{{GPURenderPassEncoder/[[maxDrawCount]]}} to |descriptor|.{{GPURenderPassDescriptor/maxDrawCount}}.

1. [$Enqueue a command$] on |this| which issues the subsequent steps on the
[=Queue timeline=] when executed.
Expand All @@ -9607,10 +9608,72 @@ dictionary GPUCommandEncoderDescriptor

1. Let the {{GPUCommandBuffer/[[renderState]]}} of the currently executing
{{GPUCommandBuffer}} be a new [=RenderState=].
1. Issue: Perform attachment loads/clears.
</div>

Issue: specify the behavior of read-only depth/stencil
1. Set {{GPUCommandBuffer/[[renderState]]}}.{{RenderState/[[colorAttachments]]}} to
|descriptor|.{{GPURenderPassDescriptor/colorAttachments}}.
1. Set {{GPUCommandBuffer/[[renderState]]}}.{{RenderState/[[depthStencilAttachment]]}} to
|descriptor|.{{GPURenderPassDescriptor/depthStencilAttachment}}.

1. For each non-`null` |colorAttachment| in |descriptor|.{{GPURenderPassDescriptor/colorAttachments}}:
1. Let |colorView| be |colorAttachment|.{{GPURenderPassColorAttachment/view}}.
1. If |colorView|.{{GPUTextureView/[[descriptor]]}}.{{GPUTextureViewDescriptor/dimension}} is:
<dl class=switch>
: {{GPUTextureViewDimension/"3d"}}
::
Let |colorSubregion| be |colorAttachment|.{{GPURenderPassColorAttachment/depthSlice}} of
|colorView|.

: Otherwise
::
Let |colorSubregion| be |colorView|.
</dl>

1. If |colorAttachment|.{{GPURenderPassColorAttachment/loadOp}} is:
<dl class=switch>
: {{GPULoadOp/"load"}}
::
Ensure the contents of |colorSubregion| are loaded into the [=framebuffer memory=]
associated with |colorSubregion|.

: {{GPULoadOp/"clear"}}
::
Set every [=texel block|texel=] of the [=framebuffer memory=] associated with
|colorSubregion| to |colorAttachment|.{{GPURenderPassColorAttachment/clearValue}}.
</dl>

1. If |depthStencilAttachment| is not `null`:
1. If |depthStencilAttachment|.{{GPURenderPassDepthStencilAttachment/depthLoadOp}} is:
<dl class=switch>
: {{GPULoadOp/"load"}}
::
Ensure the contents of the [=aspect/depth=] [=GPUTextureView/subresource=] of
|depthStencilView| are loaded into the [=framebuffer memory=] associated with
|depthStencilView|.

: {{GPULoadOp/"clear"}}
::
Set every [=texel block|texel=] of the [=framebuffer memory=] associated with the
[=aspect/depth=] [=GPUTextureView/subresource=] of |depthStencilView| to
|depthStencilAttachment|.{{GPURenderPassDepthStencilAttachment/depthClearValue}}.
</dl>

1. If |depthStencilAttachment|.{{GPURenderPassDepthStencilAttachment/stencilLoadOp}} is:
<dl class=switch>
: {{GPULoadOp/"load"}}
::
Ensure the contents of the [=aspect/stencil=] [=GPUTextureView/subresource=] of
|depthStencilView| are loaded into the [=framebuffer memory=] associated with
|depthStencilView|.

: {{GPULoadOp/"clear"}}
::
Set every [=texel block|texel=] of the [=framebuffer memory=] associated with the
[=aspect/stencil=] [=GPUTextureView/subresource=] |depthStencilView| to
|depthStencilAttachment|.{{GPURenderPassDepthStencilAttachment/stencilClearValue}}.
</dl>

Issue: specify the behavior of read-only depth/stencil
</div>
</div>

: <dfn>beginComputePass(descriptor)</dfn>
Expand Down Expand Up @@ -10915,8 +10978,20 @@ When executing encoded render pass commands as part of a {{GPUCommandBuffer}}, a

: <dfn>\[[stencilReference]]</dfn>, of type {{GPUStencilValue}}
:: Current stencil reference value, initially `0`.

: <dfn>\[[colorAttachments]]</dfn>, of type [=sequence=]&lt;{{GPURenderPassColorAttachment}}?&gt;
:: The color attachments and state for this render pass.

: <dfn>\[[depthStencilAttachment]]</dfn>, of type {{GPURenderPassDepthStencilAttachment}}?
:: The depth/stencil attachment and state for this render pass.
</dl>

Render passes also have <dfn dfn>framebuffer memory</dfn>, which contains the [=texel block|texel=] data associated with
each attachment that is written into by draw commands and read from for blending and depth/stencil testing.

Note: Depending on the GPU hardware, [=framebuffer memory=] may be the memory allocated by the attachment textures or
may be a separate area of memory that the texture data is copied to and from, such as with tile-based architectures.

### Render Pass Encoder Creation ### {#render-pass-encoder-creation}

<script type=idl>
Expand Down Expand Up @@ -11481,8 +11556,69 @@ called the render pass encoder can no longer be used.
<div data-timeline=queue>
[=Queue timeline=] steps:

1. Issue: Perform the attachment stores/discards.
1. For each non-`null` |colorAttachment| in |renderState|.{{RenderState/[[colorAttachments]]}}:
1. Let |colorView| be |colorAttachment|.{{GPURenderPassColorAttachment/view}}.
1. If |colorView|.{{GPUTextureView/[[descriptor]]}}.{{GPUTextureViewDescriptor/dimension}} is:
<dl class=switch>
: {{GPUTextureViewDimension/"3d"}}
::
Let |colorSubregion| be |colorAttachment|.{{GPURenderPassColorAttachment/depthSlice}} of
|colorView|.

: Otherwise
::
Let |colorSubregion| be |colorView|.
</dl>

1. If |colorAttachment|.{{GPURenderPassColorAttachment/resolveTarget}} is not `null`:
1. Resolve the multiple samples of every [=texel block|texel=] of |colorSubregion| to a single
sample and copy to |colorAttachment|.{{GPURenderPassColorAttachment/resolveTarget}}.

1. If |colorAttachment|.{{GPURenderPassColorAttachment/loadOp}} is:
<dl class=switch>
: {{GPUStoreOp/"store"}}
::
Ensure the contents of the [=framebuffer memory=] associated with |colorSubregion|
are stored in |colorSubregion|.

: {{GPUStoreOp/"discard"}}
::
Set every [=texel block|texel=] of |colorSubregion| to zero.
</dl>

1. Let |depthStencilAttachment| be |renderState|.{{RenderState/[[depthStencilAttachment]]}}.
1. If |depthStencilAttachment| is not `null`:
1. If |depthStencilAttachment|.{{GPURenderPassDepthStencilAttachment/depthLoadOp}} is:
<dl class=switch>
: {{GPUStoreOp/"store"}}
::
Ensure the contents of the [=framebuffer memory=] associated with the [=aspect/depth=]
[=GPUTextureView/subresource=] of |depthStencilView| are stored in |depthStencilView|.

: {{GPUStoreOp/"discard"}}
::
Set every [=texel block|texel=] in the [=aspect/depth=] [=GPUTextureView/subresource=]
of |depthStencilView| to zero.
</dl>

1. If |depthStencilAttachment|.{{GPURenderPassDepthStencilAttachment/stencilLoadOp}} is:
<dl class=switch>
: {{GPUStoreOp/"store"}}
::
Ensure the contents of the [=framebuffer memory=] associated with the [=aspect/stencil=]
[=GPUTextureView/subresource=] of |depthStencilView| are stored in |depthStencilView|.

: {{GPUStoreOp/"discard"}}
::
Set every [=texel block|texel=] in the [=aspect/stencil=] [=GPUTextureView/subresource=]
|depthStencilView| to zero.
</dl>

1. Let |renderState| be `null`.

Note: Discarded attachments behave as if they are cleared to zero, but implementations are not required
to perform a clear at the end of the render pass. See the note on {{GPUStoreOp/"discard"}} for
additional details.
</div>
</div>
</div>
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