[Bug 74700] Dota2 shimmering artifacts on Mesa 10.0.1 on Iris Pro graphics

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=74700

Jordan Justen <jljusten at gmail.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |cworth at cworth.org,
                   |                            |mattst88 at gmail.com

--- Comment #3 from Jordan Justen <jljusten at gmail.com> ---
I have observed that disabling GL_DITHER will
remove this undesirable rendering.

DOTA2 is rendering to a framebuffer bound to an
RGB10_A2 texture when the corruption first appears
to happen. The undesirable rendering appears on the
alpha channel.

It doesn't appear that DOTA2 gets or sets GL_DITHER.
According to the OpenGL spec, dithering is enabled
by default, but Matt Turner also points out that
the spec notes in "Appendix B Corollaries":
"Dithering algorithms may be different for
different components. In particular, alpha may
be dithered differently from red, green, or blue,
and an implementation may choose to not dither
alpha at all."

So, it appears that other implementations may
disable dithering for alpha, or perhaps only for
alpha on RGB10_A2.

A question regarding DOTA2: Does it specifically
want GL_DITHER enabled?

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