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Re: [Public WebGL] GL_MAX_TEXTURE_SIZE power of two ?



That's actually a misreading of the stat. What it's saying is that at least 14% of people support a max texture size of 16320 (NPOT), which includes the people that support 16384 (POT). What you need to look at is the difference between the two numbers, which indicates that only 151 people reported a MAX_TEXTURE_SIZE of 16320.


On Mon, Jul 15, 2013 at 12:46 PM, Zhenyao Mo <zmo@chromium.org> wrote:
The assumption that GL_MAX_TEXTURE_SIZE is POT is not true.  If you
look at http://webglstats.com/#h_texsize, 14% of users' GPUs do not
meet this.

Mo

On Mon, Jul 15, 2013 at 12:35 PM, Brandon Jones <bajones@google.com> wrote:
> It seems to me that if that assumption is being made it should be specified
> in the ES 2.0 spec, but barring that could we at least make this behavior
> explicit in the WebGL spec?
>
> --Brandon
>
>
> On Mon, Jul 15, 2013 at 12:25 PM, Kenneth Russell <kbr@google.com> wrote:
>>
>>
>> While I agree from looking at the OpenGL ES 2.0 specification that
>> this isn't 100% clear, the assumption in OpenGL for a very long time
>> has been that GL_MAX_TEXTURE_SIZE is a power of two, and that textures
>> allocated at that size can have glGenerateMipmaps called against them
>> (even without NPOT texture support). I think that the test should
>> remain as is, and that the workaround in Gecko should be changed to
>> round down MAX_TEXTURE_SIZE to 4096 on GPUs that can't properly
>> support textures of width and/or height 8192.
>>
>> -Ken
>>
>>
>>
>> On Mon, Jul 15, 2013 at 11:34 AM, Guillaume Abadie
>> <guillaume.abadie@gmail.com> wrote:
>> >
>> > Hi all,
>> >
>> > Gecko is having a regression on the WebGL conformance test
>> > https://www.khronos.org/registry/webgl/conformance-suites/1.0.2/conformance/limits/gl-max-texture-dimensions.html
>> > because it return a non power of two MAX_TEXTURE_SIZE = 8191 because of a
>> > driver bug work around on Mac OS X (that is having bugs with 8k textures).
>> > And we have chosen to set MAX_TEXTURE_SIZE = 8191 instead of 4096 to allow
>> > bigger textures even we can't have 8192.
>> >
>> > The problem is this WebGL test is assuming that MAX_TEXTURE_SIZE is a
>> > power of two because create a texture of size (MAX_TEXTURE_SIZE, 1) and try
>> > to generate its mipmap which fail because WebGL 1.0 is suppose to only
>> > support power of two texture mipmaps. But I can't see in any OpenGL (ES or
>> > not) specification that MAX_TEXTURE_SIZE have to be a power of 2. The only
>> > paragraph that is close and ambiguous to that issues is :
>> >
>> > http://www.khronos.org/registry/gles/specs/2.0/es_full_spec_2.0.25.pdf
>> > (paragraphe 3.7 - Texturing - p69)
>> > "The maximum allowable width and height of a two-dimensional texture
>> > image must be at least 2^(k-lod) for image arrays of level zero through k,
>> > where k is the log base 2 of MAX_TEXTURE_SIZE"
>> > We don't know if this given k is only an integer, or can be a real.
>> >
>> > Therefore, my question is : Does our WebGL API should always return a
>> > power of two value for MAX_TEXTURE_SIZE, or the test should handle this case
>> > ?
>> >
>> > Thanks you !
>> >
>> > Guillaume Abadie.
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