[Mesa-dev] Bug in _mesa_meta_GenerateMipmap

[Brian Paul]

Maciej Cencora wrote:
> Dnia poniedziałek 12 lipca 2010 o 20:31:42 Brian Paul napisał(a):
>> Maciej Cencora wrote:
>>> Hi,
>>>
>>> while working on failing piglit tests I've stumbled on a problem with
>>> _mesa_meta_GenerateMipmap. The function creates new texture images for
>>> lower mipmap levels, but during call to glTexImage the format and type
>>> are hardcoded to GL_RGBA and GL_UNSIGNED_BYTE respectivily. And that's
>>> where the problem arise because base image (the one that other levels
>>> are generated from) could have other format and type specified (in
>>> failing test texturing/gen-teximage these are GL_RGBA, GL_FLOAT).
>>> The result is that for base image MESA_FORMAT_ARGB8888 is chosen and for
>>> next levels it's MESA_FORMAT_RGBA8888_REV. Of course such texture with
>>> images of different formats is invalid and will be missampled by GPU.
>>>
>>> As the fix is not straightforward for me (not sure where to get format
>>> and type from, since the gl_texture_image doesn't hold them) could
>>> someone more familiar with core mesa take a look at this?
>> Which driver are you using?
>>
>> I suspect the problem is the driver's ChooseTextureFormat() callback
>> is using more than the 'internalFormat' parameter to choose the actual
>> hardware format (i.e. it's also using the format/type params).  Later,
>> when we're building the mipmap we don't know the format/type params
>> used for creating the base image so we just use GL_RGBA/GL_UNSIGNED_BYTE.
>>
>> We could save those original params when glTexImage2D() is called to
>> create the base image, but that would be of no use if the base image
>> was created with glCopyTexImage2D().
>>
>> We might just be able to "poke" in the actual format for the new image
>> to override whatever was chosen.  I'll try to write a patch later...
>>
>> -Brian
> 
> I'm using r300 driver. As you suspect the radeonChooseTextureFormat 
> (radeon_texture.c) function takes into account format and type to avoid 
> unnecessary conversions in TexImage callback.

Here's a patch to try.  Totally untested.

-Brian

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