https://bugs.freedesktop.org/show_bug.cgi?id=45913
Paul Berry <stereotype...@gmail.com> changed:
What |Removed |Added
----------------------------------------------------------------------------
Keywords|regression |
--- Comment #1 from Paul Berry <stereotype...@gmail.com> 2012-02-10 15:22:48
PST ---
Before commit 7d68c639ddb0f9df45cf698b8e8227bf1860b5fe, Mesa's support for
gl_ClipVertex was completely broken, because Mesa couldn't distinguish between
gl_ClipVertex and gl_Position. The bugs in Mesa happened to line up in such a
way that the Piglit test vs-clip-vertex-const-reject passed, but this was not a
sign that gl_ClipVertex in any way worked; it was just a coincidence.
Commit 7d68c639ddb0f9df45cf698b8e8227bf1860b5fe laid the groundwork for actual
non-buggy support for gl_ClipVertex, and a later patch. However, it was
impossible to lay this groundwork without causing vs-clip-vertex-const-reject
to stop passing. This is not a true regression, because
vs-clip-vertex-const-reject was only passing by dumb luck before this commit;
it wasn't passing because of any correct functionality in Mesa.
In order for gl_ClipVertex to work on any particular driver (for example r300g
or llvmpipe), additional back-end work needs to be done. I have done this
back-end work for i965 (see commit d912669034eb7bf5c162358a7a574ec7a4c963c7).
However, I don't have the expertise to do it for other back-ends. If anyone who
is knowledgeable about r300g RV530 or llvmpipe would like to do the
corresponding back-end work for those drivers, I would be happy to help--feel
free to email
me at stereotype...@gmail.com if commit
d912669034eb7bf5c162358a7a574ec7a4c963c7 doesn't provide enough information.
Incidentally, the same situation also exists for i915.
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