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Re: [Public WebGL] Re: meaning of the specification of FBO sampling and interpretation by UAs



We have WebGL conformance tests for feedback loop detection, but we
don't have a positive test that a texture is bound but not sampled,
that it is not feedback loop and no error should be generated.

The ES spec doesn't generate GL errors on feedback loops.  It's simply
stating the results are undefined.

On Mon, Mar 20, 2017 at 9:48 AM, Florian Bösch <pyalot@gmail.com> wrote:
> I'm not 100% sure it's the case, the error I looked at was somewhat complex.
> Do we have unit-test for it?
>
> On Mon, Mar 20, 2017 at 5:46 PM, Zhenyao Mo <zmo@chromium.org> wrote:
>>
>> To clarify, drivers never generate errors in such situation.  It's
>> simply an undefined behavior.  The error you see is not from NVidia
>> drivers, but from Chrome's GPU command buffer.
>>
>> On Sun, Mar 19, 2017 at 2:07 PM, Florian Bösch <pyalot@gmail.com> wrote:
>> > I might add, OpenGL adopts the latter more lenient interptation (at
>> > least
>> > with nvidia drivers),  and that works fine on Chrome on these systems,
>> > but
>> > on Windows Chrome/ANGLE use a more strict interpretation.
>> >
>> > On Sun, Mar 19, 2017 at 10:05 PM, Florian Bösch <pyalot@gmail.com>
>> > wrote:
>> >>
>> >> The ES specification states that the result of sampling from a texture
>> >> attached to a framebuffer at the same time as sampling to that
>> >> framebuffer
>> >> is undefined.
>> >>
>> >> Google chrome seems to interprete this as: If a texture is bound to any
>> >> texturing unit while that framebuffer is used it's an error.
>> >>
>> >> However a different interpretation of this would be: If a texture that
>> >> is
>> >> bound is actually sampled during the framebuffer operation it's an
>> >> error.
>> >>
>> >> Which of these interpretations is the correct one?
>> >
>> >
>
>

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