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




On Aug 27, 2010, at 10:28 PM, Cedric Vivier wrote:

On Wed, Aug 25, 2010 at 12:00, Cedric Vivier <cedricv@neonux.com> wrote:
Of course if NaCl on Windows Chrome is _not_ supposed to ever run on top of Direct3D/Angle then my question is moot and I apologize for the being a bit off-topic.

With the news of Chrome jumping into the GPU-accelerated HTML compositing train as well, I stumbled upon an interesting document about how Chrome handles accelerated compositing, WebGL content and NaCl 3D rendering within the same "GPU process" :

After reading this article (and glancing at the code) I'm still very curious how NaCl can be fully ES 2.0 conformant with no restriction similar to WebGL spec section 6.3 when running on top of OpenGL desktop and Direct3D/ANGLE.

Has a solution to reliably emulate the ES 2.0 semantics been developed somehow ?
If so, assuming the same trick can be done on any WebGL implementation, do we still need to keep section 6.3 (and the divergence from ES 2.0 it brings) ?

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

As far as compositing goes webkit determines what content should be placed in a compositing layer then, then asks the compositing engine for a new layer, draws the appropriate content into that layer, and from that point onwards relies on the compositing engine to composite that layer correctly.  This can even be done in software (and has been done by Nokia in the Qt backend - it does actually provide a perf win vs the non-compositing model in some cases).

--Oliver