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Re: [Public WebGL] copyTexImage2D and copyTexSubImage2D



On Tue, Jan 4, 2011 at 2:17 PM, Benoit Jacob <bjacob@mozilla.com> wrote:
> ----- Original Message -----
>> Hi list,
>>
>> I am still waiting for input on my question.
>>
>> For copyTexSubImage2D, there are two available options for undefined
>> pixels (that are outside framebuffer boundaries).
>>
>> 1) clamp, so these pixels stay the same before/after copyTexSubImage2D
>> 2) set to 0
>
> I would like us to standardize on 2) set to 0, for example because, as you mention, this is what we're already specing for readPixels().

OK, this sounds good. I've updated the current working draft to
document this under copyTexImage2D and copyTexSubImage2D, and added a
new subsection under Section 6 also documenting the defined behavior
for readPixels.

-Ken

> Benoit
>
>>
>> One way or the other, I think we should explicitly specify it in the
>> WebGL spec. This has the potential of leaking information, so we
>> definitely need to have a conformance test for it. However, before we
>> decide to go 1) or 2), it's hard to write the test.
>>
>> Mo
>>
>> On Thu, Dec 23, 2010 at 2:23 PM, Mo, Zhenyao <zhenyao@gmail.com>
>> wrote:
>> > Ok, but that doesn't cover the case for copyTexSubImage2D. We can
>> > initialize undefined pixels to 0 or make sure they stay untouched. I
>> > am fine with either, but I think we should specify one so we could
>> > test against it. Otherwise there is no way to write a test.
>> >
>> > On Thu, Dec 23, 2010 at 2:18 PM, Gregg Tavares (wrk)
>> > <gman@google.com> wrote:
>> >> This is mostly already speced.
>> >>
>> >> Section 4.1
>> >> "WebGL resources such as textures and vertex buffer objects (VBOs)
>> >> must
>> >> always contain initialized data, even if they were created without
>> >> initial
>> >> user data values"
>> >>
>> >>
>> >>
>> >> On Thu, Dec 23, 2010 at 9:58 AM, Mo, Zhenyao <zhenyao@gmail.com>
>> >> wrote:
>> >>>
>> >>> In WebGL spec, we say "For any pixel lying outside the frame
>> >>> buffer,
>> >>> the value read contains 0 in all channels" for readPixels.
>> >>> Shouldn't
>> >>> we say the same thing for copyTexImage2D?
>> >>>
>> >>> As in the case of copyTexSubImage2D, pixels outside the frame
>> >>> buffer
>> >>> could be cleared to 0, or could be untouched. The latter would be
>> >>> more efficient. However, whatever way we decide, it should be made
>> >>> explicit, so we could have conformance test against it.
>> >>> "Undefined"
>> >>> is unacceptable for security reasons.
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>> >>
>> >
>>
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