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Re: [Public WebGL] Updated WebGL spec with bounds checking info



On Thu, May 26, 2011 at 11:28 PM, Tim Johansson <timj@opera.com> wrote:
>
> Some comments:
>
> <h3><a name="OUT_OF_RANGE_ARRAY_ACCESSES">Out-of-Range Array Accesses</h3>
> <h3><a name="DYNAMIC_INDEXING_OF_ARRAYS">Dynamic Indexing of Arrays</h3>
>
> The lack of </a> in these headers breaks rendering for me.

Since it looks like Chris is busy I've fixed these.

> In 6.20 there is no mention of array of samplers (which are uniforms), I
> really think we should disallow arrays of samplers as they will not work on
> all GLES implementations, we have already run into at least one where it
> does not work.

Appendix A, section 5 of the GLSL ES specification specifically
indicates that GLSL ES 1.00 supports arrays of samplers. We've run
into problems with them too (on Mac in particular) but I think that we
should not forbid their use in WebGL but instead work around any
issues in WebGL implementations.

> What should happen if you try to index using a non constant expression? I
> would prefer if compilation fails as it is an error in the shader, this is
> how gles implementations seems to handle it and it would make writing
> conformance tests for it easy. Do we need to mention this or is it implied?

It is implied that shader compilation should fail -- the language
construct is simply not supported.

I'll raise some other concerns about the new sections in a separate email.

-Ken

> //Tim
>
> On 2011-05-26 20:18, Chris Marrin wrote:
>>
>> I've just added two new sections to the WebGL editor's draft:
>>
>>        https://www.khronos.org/registry/webgl/specs/latest/#4.5
>>        https://www.khronos.org/registry/webgl/specs/latest/#6.20
>>
>> Please review for accuracy and clarity...
>>
>> -----
>> ~Chris
>> cmarrin@apple.com
>>
>>
>>
>>
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