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Re: [Public WebGL] Is section 6.3 still needed ? (was: New Rendering Pipeline ?)



On Fri, Aug 27, 2010 at 11:27 PM, Cedric Vivier <cedricv@neonux.com> wrote:
> On Sat, Aug 28, 2010 at 13:59, Oliver Hunt <oliver@apple.com> wrote:
>>
>> Compositing is a highly restricted use case, it is quite literally the act
>> of drawing one texture on top of another, with no effects or anything. If
>> there were compatibility problems doing something that simple then i don't
>> think we'd have much in the way of consumer products that used 3d :D
>
>
> Yes indeed, but let's forget about the compositing part actually ;-)
> The interesting point is that the underlying GPU process (and the command
> buffer API) used is the same for both WebGL and NaCl 3D rendering.
> Both WebGL and NaCl expose ES 2.0 functionality to user code (WebGL doing it
> with just a bit more restrictions and adaptations with regards to
> JavaScript).
> Months ago we decided to add section 6.3 divergence to the WebGL
> specification because it was thought impossible to implement ES 2.0's
> framebuffer attachment semantics on top of OpenGL desktop and Direct3D...
> however it seems that a workaround has been found since ES 2.0 as exposed by
> NaCl is said to be able to support ES 2.0 semantics regardless of the
> underlying platform's 3D API.
> This makes me wonder whether we might be able to remove 6.3, hence have one
> less divergence from ES 2.0, which is one of the goals of WebGL ("conforms
> closely to the ES 2.0 API") and helps porting.

Section 6.3 of the WebGL specification is still needed. Adding the
extra depth+stencil virtual attachment point works around problems
when building WebGL on top of desktop GL; in particular, avoiding the
need to allocate a packed depth+stencil renderbuffer all the time
behind the scenes. I believe this is what ANGLE does.

-Ken
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