On Tue, Aug 25, 2015 at 4:19 PM, Chad Versace <chad.vers...@intel.com> wrote:
> On Sun 16 Aug 2015, Nanley Chery wrote: > > The last line of the commit message should say: > > > > GL_RGBA4_S3TC (0x83A3) -> COMPRESSED_RGBA_S3TC_DXT5_EXT (0x83F3) > > There's another weird line too, see below. > > > On Wed, Aug 12, 2015 at 4:19 PM, Nanley Chery <nanleych...@gmail.com> > wrote: > > > > > From: Nanley Chery <nanley.g.ch...@intel.com> > > > > > > This function's cases for non-generic compressed formats duplicate > > > the GL to MESA translation in _mesa_glenum_to_compressed_format(). > > > This patch replaces the switch cases with a call to the translation > > > function. There are no behavioral changes except for the RGB[A]4 > formats: > > > > > > case GL_RGB4_S3TC: > > > return MESA_FORMAT_RGB_DXT1 (old) -> MESA_FORMAT_RGBA_DXT1 (new) > ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ > > I have trouble believing this line is correct. It adds an alpha channel. > Can you provide the documentation for that translation? > > Since this mapping is nowhere explicitly defined, I was leaning on the fact that _mesa_glenum_to_compressed_format() uses this mapping and the last byte of the enums (coincidentally) match up. I did some more/better research however and I now think that _mesa_choose_tex_format() had the correct mapping for several reasons: * The GL_RGB4_S3TC and GL_RGBA4_S3TC formats are formats that the driver can chose if the user passes in GL_RGB_S3TC and GL_RGBA_S3TC respectively. Therefore, it's not a problem for the formats to map to the same mesa_format (according to http://homepage.ntlworld.com/neal.tringham/OpenGLGameDev/s3tcoglext.htm) * MESA_FORMAT_RGBA_DXT5 should be reserved for the RGBA[4]_DXT5_S3TC cases we currently aren't handling ( https://www.opengl.org/registry/specs/S3/s3tc.txt) * The mapping in _mesa_choose_tex_format() can also be found in nouveau_choose_tex_format(), radeonChooseTextureFormat(), and in st_format.c's format_map[]. Thank you for the feedback. I will send out another patch to correct _mesa_glenum_to_compressed_format() and (if R-b'd) will omit the note about the behavioral change in this patch. I could also send out a v2 with an updated commit message if you'd prefer. Thanks, Nanley > > case GL_RGBA4_S3TC: > > > return MESA_FORMAT_RGBA_DXT3 (old) -> MESA_FORMAT_RGBA_DXT5 (new) > > > > > > Although unclear, the old behavior was likely a bug, given that online > > > documentation (few and far between) imply a format mapping of the > > > following: > > > > > > GL_RGB_S3TC (0x83A0) -> COMPRESSED_RGB_S3TC_DXT1_EXT (0x83F0) > > > GL_RGB4_S3TC (0x83A1) -> COMPRESSED_RGBA_S3TC_DXT1_EXT (0x83F1) > > > GL_RGBA_S3TC (0x83A2) -> COMPRESSED_RGBA_S3TC_DXT3_EXT (0x83F2) > > > GL_RGBA4_S3TC (0x83A2) -> COMPRESSED_RGBA_S3TC_DXT5_EXT (0x83F2) > > > > > > Cc: Brian Paul <bri...@vmware.com> > > > Cc: Ian Romanick <ian.d.roman...@intel.com> > > > Signed-off-by: Nanley Chery <nanley.g.ch...@intel.com> > > > --- > > > src/mesa/main/texformat.c | 94 > > > +++++++---------------------------------------- > > > 1 file changed, 13 insertions(+), 81 deletions(-) >
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