[Mesa-dev] [PATCH] mesa: do more teximage error checking for generic compressed formats

[Anuj Phogat]

On Fri, Aug 17, 2012 at 8:28 PM, Ian Romanick <idr at freedesktop.org> wrote:
> On 08/16/2012 02:29 PM, Anuj Phogat wrote:
>>
>> On Thu, Aug 16, 2012 at 10:23 AM, Brian Paul <brianp at vmware.com> wrote:
>>>
>>> On 08/15/2012 02:31 PM, Anuj Phogat wrote:
>>>>
>>>>
>>>> On Tue, May 1, 2012 at 2:07 PM, Brian Paul <brianp at vmware.com
>>>> <mailto:brianp at vmware.com>> wrote:
>>>>
>>>>      When glTexImage or glCopyTexImage is called with internalFormat
>>>>      being a
>>>>      generic compressed format (like GL_COMPRESSED_RGB) we need to do
>>>>      the same
>>>>      error checks as for specific compressed formats.  In particular,
>>>>      check if
>>>>      the texture target is compatible with the format.  None of the
>>>> texture
>>>>      compression formats we support so far work with GL_TEXTURE_1D, for
>>>>      example.
>>>>
>>>>      See also https://bugs.freedesktop.org/show_bug.cgi?id=49124
>>>>
>>>>
>>>> Brian, generic texture compression formats with GL_TEXTURE_1D seem to
>>>> work fine
>>>> on i965 drivers.
>>>
>>>
>>> Does that wind up using one of the DXT formats?
>>
>> It uses RGTC for GL_COMPRESSED_RED & GL_COMPRESSED_RG
>> FXT for GL_COMPRESSED_RGB & GL_COMPRESSED_RGBA
>
>
> I wonder if that produces correct results.  There are lots of limitations
> with those formats...
>
I noticed failures in case of GL_TEXTURE_3D with GL_COMPRESSED_RGBA
format. Failures disappeared when I made changes to pick an uncompressed
format.
>>>   I verified this by allowing generic texture
>>>>
>>>>
>>>> compression formats for
>>>> GL_TEXTURE_1D in piglit copyteximage test case and reverting the
>>>> changes due to
>>>> this patch on mesa. Is this an issue only on swrast?
>>>
>>>
>>>
>>> That's what the bug reported, don't recall testing other drivers.
>>>
>>>
>>>
>>>> Returning
>>>> GL_INVALID_ENUM
>>>> error for generic texture compression formats in glTexImage1D() and
>>>> glCopyTexImage1D() doesn't seem to follow the OpenGL
>>>> specification. Spec does allow
>>>> GL_INVALID_ENUM error for a similar scenario in case
>>>> of glCompressedTexImage1D().
>>>> Please correct me if I'm missing something.
>>>
>>>
>>>
>>> I guess I'd like to check what either NVIDIA or AMD do in some of these
>>> cases.
>>>
>>> AFAIK, the various DXT, LATC, etc compressed formats are only spec'd to
>>> work
>>> with 2D textures, not 1D.  Since 1D textures are generally pretty small
>>> to
>>> start with, there's not a lot of value in compressed 1D textures.  Plus,
>>> if
>>> a compressed 1D texture uses 4 or 8 bytes to store a 4x1 block of texels,
>>> there's only 50% or 0% memory savings with compression.
>
>
> Most of the specific formats are specified to only work with 2D textures.
>
> From EXT_texture_compression_s3tc (note that 1D variants of TexImage,
> CopyTexImage, etc are missing):
>
>     Accepted by the <internalformat> parameter of TexImage2D,
> CopyTexImage2D,
>     and CompressedTexImage2DARB and the <format> parameter of
>     CompressedTexSubImage2DARB:
>
>         COMPRESSED_RGB_S3TC_DXT1_EXT                   0x83F0
>         COMPRESSED_RGBA_S3TC_DXT1_EXT                  0x83F1
>         COMPRESSED_RGBA_S3TC_DXT3_EXT                  0x83F2
>         COMPRESSED_RGBA_S3TC_DXT5_EXT                  0x83F3
>
> Same for 3DFX_texture_compression_FXT1:
>
>     Accepted by the <internalformat> parameter of TexImage2D,
>     CopyTexImage2D, TexImage3D, CopyTexImage3D, and by the
>     <internalformat> and <format> parameters of
>     CompressedTexImage2D_ARB, CompressedTexSubImage2D_ARB,
>     CompressedTexImage3D_ARB, CompressedTexSubImage3D_ARB:
>
>         COMPRESSED_RGB_FXT1_3DFX                          0x86B0
>         COMPRESSED_RGBA_FXT1_3DFX                         0x86B1
>
> However, the generic formats should be accepted.  From
> ARB_texture_compression:
>
>     Accepted by the <internalformat> parameter of TexImage1D, TexImage2D,
>     TexImage3D, CopyTexImage1D, and CopyTexImage2D:
>
>         COMPRESSED_ALPHA_ARB                            0x84E9
>         COMPRESSED_LUMINANCE_ARB                        0x84EA
>         COMPRESSED_LUMINANCE_ALPHA_ARB                  0x84EB
>         COMPRESSED_INTENSITY_ARB                        0x84EC
>         COMPRESSED_RGB_ARB                              0x84ED
>         COMPRESSED_RGBA_ARB                             0x84EE
>
> When the application specifies a generic format, the driver is always free
> to pick an uncompressed format.  Many Mesa drivers (primarily the ones we
> removed a couple years ago) have done that for ages. :)
>
ok. I will make changes to allow these formats for 1D/3D textures as well and
and pick a matching uncompressed format internally.
Do we need any special treatment for 2D textures? I mean picking a matching
compressed format as they are well supported on 2D targets.

>>> If you can post your patch for the piglit test I can run it with the
>>> NVIDIA
>>> driver and see what it does.
>>
>> I'll send out a follow up patch for piglit test case which you can use
>> for testing.
>>
>>>
>>> -Brian
>>
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