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Clarify that opaque textures are always initialized at the start of the frame #234

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Merged
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Dec 17, 2020
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Clarify that opaque textures are always initialized at the start of the frame #234

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f099209
Merge pull request #50 from immersive-web/master
cabanier Dec 16, 2020
2051ae3
State that opaque textures are always initialized at the start of the…
cabanier Dec 16, 2020
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State that opaque textures are always initialized at the start of the… 
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@cabanier
cabanier committed Dec 16, 2020
commit 2051ae3eabb71277b813cc5a36e2eff5e237129c
25 changes: 25 additions & 0 deletions webxrlayers-1.bs
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Expand Up @@ -782,6 +782,31 @@ An [=opaque texture=] functions identically to a standard {{WebGLTexture}} with
- An [=opaque texture=] MUST behave as though it was allocated with [=texStorage2D=] or [=texStorage3D=], as appropriate, even when using a WebGL 1.0 context.
- A call to {{deleteTexture}} with an [=opaque texture=] MUST generate an {{INVALID_OPERATION}} error.

The buffers attached to an [=opaque texture=] MUST be cleared to the values in the table below prior to the processing of each [=XR animation frame=].

<table class="tg">
<thead>
<tr>
<th>Buffer</th>
<th>Clear Value</th>
</tr>
</thead>
<tbody>
<tr>
<td>Color</td>
<td>(0, 0, 0, 0)</td>
</tr>
<tr>
<td>Depth</td>
<td>1.0</td>
</tr>
<tr>
<td>Stencil</td>
<td>0</td>
</tr>
</tbody>
</table>

NOTE: the [=opaque texture|opaque textures=] are allocated when the layer is contructed using the
[=allocate color textures=] and [=allocate depth textures=] algoritms. The side effect of this pre-allocation is that calling
{{XRWebGLBinding/getSubImage()}} and {{XRWebGLBinding/getViewSubImage()}} with the same parameters will always return the same texture objects.
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