[Mesa-dev] [PATCH] mesa: fix maximum supported texture size returned by glGetIntegrv

[Ian Romanick]

On 01/27/2012 12:57 AM, Jose Fonseca wrote:
> This doesn't make sense from a mathematical POV.
>
> If the allowable size is
>
>    2^floor(log2(MAX_XX_TEXTURE_SIZE)) + 2*bt
>
> then it doesn't matter whether MAX_XX_TEXTURE_SIZE has or not the
> border with, as the allowable size is still the same for all common
> values of MAX_XX_TEXTURE_SIZE.
>
> It would be very odd to define MAX_XX_TEXTURE_SIZE in terms of
> itself, as there would be a singularity for MAX_XX_TEXTURE_SIZE< 4 :
> no value of MAX_XX_TEXTURE_SIZE under four will satisfy the
> equation:
>
>    MAX_XX_TEXTURE_SIZE = 2^floor(log2(MAX_XX_TEXTURE_SIZE)) + 2
>
> If hypothetically one day the spec allowed higher maximum border sizes, it would be even worse.

Which it won't: borders are removed in OpenGL ES and in OpenGL 3.1+ Core 
profile.

> My take is that the border does not need to be implicitly added to
> MAX_XX_TEXTURE_SIZE query, and the test/driver is wrong.
>
> Also it doesn't match what NVIDIA produces:

Thanks for checking this.  I was going to check it, but I kept getting 
distracted.

I think the proxy check needs to change.  If the maximum texture size is 
2048, then a texture with border should be limited to 2046+2.  That is, 
when doing the size check, add the border size in first.  I just tried 
the test on AMD and NVIDIA, and this appears to be what they both do.

My recollection is also that the test just produces a warning in this case.

> $ glxinfo -l | grep SIZE
>      GL_MAX_TEXTURE_SIZE = 16384
>      GL_MAX_3D_TEXTURE_SIZE = 2048
>      GL_ALIASED_POINT_SIZE_RANGE = 1, 63
>      GL_SMOOTH_POINT_SIZE_RANGE = 1, 63
>      GL_MAX_CUBE_MAP_TEXTURE_SIZE_ARB = 16384
>      GL_MAX_RECTANGLE_TEXTURE_SIZE_NV = 16384
>
> Jose
>
>
> ----- Original Message -----
>> As per OpenGL 3.0 specification section 3.9, page 187 in pdf the
>> maximum
>> allowable width, height, or depth of a texel array must be at least
>> 2^(k−lod) + 2*bt for image arrays of level-of-detail (lod) 0 through
>> k,
>> where k is the log base 2 of MAX_3D_TEXTURE_SIZE, and bt is the
>> maximum
>> border width
>>
>> Currently different values for maximum allowable texture size are
>> returned
>> by glGetIntegrv() and proxy textures. glGetIntegrv returns 2048 and
>> proxy
>> texture returns (2048 + 2)
>>
>> This patch fixes Intel oglconform test case: max_values
>> Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=44970
>>
>> Note: This is a candidate for mesa 8.0 branch.
>>
>> Signed-off-by: Anuj Phogat<anuj.phogat at gmail.com>
>> ---
>>   src/mesa/main/get.c |    3 ++-
>>   1 files changed, 2 insertions(+), 1 deletions(-)
>>
>> diff --git a/src/mesa/main/get.c b/src/mesa/main/get.c
>> index 5ad6012..4a70109 100644
>> --- a/src/mesa/main/get.c
>> +++ b/src/mesa/main/get.c
>> @@ -1507,7 +1507,8 @@ find_custom_value(struct gl_context *ctx, const
>> struct value_desc *d, union valu
>>      case GL_MAX_3D_TEXTURE_SIZE:
>>      case GL_MAX_CUBE_MAP_TEXTURE_SIZE_ARB:
>>         p = (GLuint *) ((char *) ctx + d->offset);
>> -      v->value_int = 1<<  (*p - 1);
>> +      /* GL 3.0: Add 2 pixels to accmodate border */
>> +      v->value_int = 1<<  (*p - 1) + 2;
>>         break;
>>
>>      case GL_SCISSOR_BOX:
>> --
>> 1.7.7.4
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