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Re: [Public WebGL] Re: double-buffering and back buffer preservation

On Nov 18, 2010, at 7:59 PM, Cedric Vivier wrote:

> On Fri, Nov 19, 2010 at 11:07, Vladimir Vukicevic <vladimir@mozilla.com> wrote:
>>> Doesn't this block usage of EXT_discard_framebuffer as it would
>>> require an additional/unnecessary "clear" ?
>> No, because that clear can happen lazily if no user clear happens before the next draw call.
> As Mark pointed out there is still many use cases that would force an
> unnecessary clear, thus limiting the advantages of discarding buffers
> wrt memory bandwidth usage.
> To avoid this could we just forbid readPixels on default framebuffer
> when preserveDrawBuffers is false?

I think that's too severe. I don't think we should worry too much about this issue. Most hardware these days, even in the mobile space (maybe even especially in the mobile case), has clear optimizations that make it much less expensive that touching every pixel in the drawing buffer. Add to that lazy clear optimizations implementations can use, and I don't think this will become a bottleneck.

And as I said in another message, security trumps performance in web browsers.


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