[Bug 57842] r200: Culling is broken when rendering to an FBO

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=57842

--- Comment #13 from Roland Scheidegger <sroland at vmware.com> ---
(In reply to comment #11)
> Created attachment 72051 [details] [review]
> attachment 72047 [details] as patch for r200/radeon
> 
> @comment 9: your own attachment says it was not.
> Anyway, attachment 72047 [details] translated into a patch.
> 
> 'cull_face = (mode == GL_CW) ? R200_FFACE_CULL_CW : R200_FFACE_CULL_CCW'
> is bit of a mouthful, but atm. I've got not idea how to turn that into
> proper obfuscation style of mesa sources.

patch looks correct to me. TCL culling is part of the tcl engine and hence
ignored if there's no TCL. But viewport transform (which is where the fbo
inversion happens) is done later, hence TCL culling is not subject to that
inversion.
FWIW it would also be possible to simply disable TCL culling, setup culling is
enough. The docs are actually saying it TCL culling is a performance
optimization with questionable quality (as the coords aren't snapped to
rasterizer subpixels). I guess it would also be possible to disable setup
culling instead (of course only with tcl) but I'm not sure if that would make
any performance compared to having enabled culling at both places.

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