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RE: [Public WebGL] consult on the webgl conformance test case



> -----Original Message-----
> From: Kenneth Russell [mailto:kbr@google.com]
> Sent: Friday, January 06, 2012 2:50 AM
> To: Mark Callow
> Cc: Zhao, Jian J; public_webgl@khronos.org
> Subject: Re: [Public WebGL] consult on the webgl conformance test case
> 
> On Thu, Jan 5, 2012 at 12:32 AM, Mark Callow <callow_mark@hicorp.co.jp>
> wrote:
> > On 05/01/2012 17:00, Zhao, Jian J wrote:
> >
> > OK. Maybe I misunderstanding the ANGLE before.
> >
> > So do you mean this is an issue in browser side(chromium or webkit)
> > instead of our 3D driver mesa's issue, is it?  And in this case it
> > still may be related to the spec or the test case.
> >
> > Thanks.
> >
> > The GLSL {,ES} specifications are not clear about how many nesting
> > levels must be supported nor the maximum lengths of identifiers and
> > the OpenGL ES conformance test does not test these things very
> > thoroughly. This has led to inconsistencies among implementations.
> > These in turn caused the WebGL WG to introduce restrictions that
> > should not be a challenge for any OpenGL {,ES} implementation in order to
> create consistency.
> >
> > The mesa 3D driver should ensure it can cope with the minimums
> > required by the WebGL spec., in this case a nesting level of 4. But it
> > is free to allow deeper nesting consistent with the GLSL
> > specification. Only WebGL implementations are required to fail
> > compilation of anything with a nesting level > 4.
> 
> Correct.
> 
> To reiterate, the WebGL shader restrictions are implemented in ANGLE's
> shader translator. This sub-component of the ANGLE project is used in
> Chromium and Firefox (and possibly other browsers) on all platforms, not just
> Windows. All incoming WebGL shaders are processed by this translator to
> enforce WebGL restrictions before giving the shader to the system's native
> GLSL or HLSL compiler.

OK. Got it.

> 
> Jian, as you pointed out in your off-list email to me, there is in fact a difference
> between the spec text and the conformance tests
> struct-nesting-under-maximum.html and
> struct-nesting-exceeds-maximum.html . The ANGLE shader translator should
> be allowing one more level of nesting than it currently does.
> I'll file a bug and fix the tests. Thanks for pointing out this issue.

Thanks very much! We will look forward for the fix. 

Best regards
zhaojian

> 
> -Ken

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