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Re: [Public WebGL] Ambiguity and Non-deterministicness in the WebGL Spec



On 16/12/2010 10:31, Chris Marrin wrote:
> On Dec 13, 2010, at 6:42 PM, Mark Callow wrote:
>
> ...
>> Another point, why does this talk about buffers? Only the color buffer is handed off for compositing so only that has the possibility to contain information from another process. So why mandate clearing the depth & stencil buffers after present?
> That's a good point. The current iOS design only makes the color buffer unavailable. I guess I was thinking that it would be better to have uniform behavior. Is it possible for other implementations to have a performance restriction on preserving the depth and stencil buffers?
Tiled renderers would prefer not to have to copy existing values from
the buffers into the tile memory, i.e. would prefer not to preserve the
contents. However I think the WebGL implementation would have to call
one of the discard extensions after presenting the color buffer in order
to avoid the copy.

Regardless, my main point is that from the security viewpoint there is
no need to mandate clearing depth and stencil. The only reason would be
for consistency across implementations.

Maybe the context attributes should let the app. specify preservation
separately for color, depth & stencil buffers with the default being
than none is preserved.

Regards

    -Mark
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