[Bug 100925] [HSW/BSW/BDW/SKL] Google Earth is not resolving all the details in the map correctly

bugzilla-daemon at freedesktop.org bugzilla-daemon at freedesktop.org
Fri May 19 00:08:42 UTC 2017


Nanley Chery <nanleychery at gmail.com> changed:

           What    |Removed                     |Added
         Resolution|---                         |FIXED
             Status|ASSIGNED                    |RESOLVED

--- Comment #18 from Nanley Chery <nanleychery at gmail.com> ---
Thank you for taking the time to report this issue. This bug has been fixed
upstream with the following commit:

commit 688ddb85c8c3357d8e1e9d360c74cd728b128d98
Author: Nanley Chery <nanley.g.chery at intel.com>
Date:   Thu May 11 15:57:59 2017 -0700

    i965/formats: Update the three-channel DXT1 mappings

    The procedure for decompressing an opaque DXT1 OpenGL format is
    dependant on the comparison of two colors stored in the first 32 bits of
    the compressed block. Here's the specified OpenGL behavior for

       The RGB color for a texel at location (x,y) in the block is given by:

          RGB0,              if color0 > color1 and code(x,y) == 0
          RGB1,              if color0 > color1 and code(x,y) == 1
          (2*RGB0+RGB1)/3,   if color0 > color1 and code(x,y) == 2
          (RGB0+2*RGB1)/3,   if color0 > color1 and code(x,y) == 3

          RGB0,              if color0 <= color1 and code(x,y) == 0
          RGB1,              if color0 <= color1 and code(x,y) == 1
          (RGB0+RGB1)/2,     if color0 <= color1 and code(x,y) == 2
          BLACK,             if color0 <= color1 and code(x,y) == 3

    The sampling operation performed on an opaque DXT1 Intel format essentially
    hard-codes the comparison result of the two colors as color0 > color1.
    This means that the behavior is incompatible with OpenGL. This is stated
    in the SKL PRM, Vol 5: Memory Views:

       Opaque Textures (DXT1_RGB)
          Texture format DXT1_RGB is identical to DXT1, with the exception that
          One-bit Alpha encoding is removed. Color 0 and Color 1 are not
compared, and
          the resulting texel color is derived strictly from the Opaque Color
          The alpha channel defaults to 1.0.

          Programming Note
          Context: Opaque Textures (DXT1_RGB)
          The behavior of this format is not compliant with the OGL spec.

    The opaque and non-opaque DXT1 OpenGL formats are specified to be
    decoded in exactly the same way except the BLACK value must have a
    transparent alpha channel in the latter. Use the four-channel BC1 Intel
    formats with the alpha set to 1 to provide the behavior required by the
    spec. Note that the alpha is already set to 1 for RGB formats in

    v2: Provide a more detailed commit message (Kenneth Graunke).
    v3: Ensure the alpha channel is set to 1 for DXT1 formats.

    Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=100925
    Cc: <mesa-stable at lists.freedesktop.org>
    Acked-by: Tapani Pälli <tapani.palli at intel.com> (v1)
    Reviewed-by: Kenneth Graunke <kenneth at whitecape.org>
    Signed-off-by: Nanley Chery <nanley.g.chery at intel.com>

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