[Bug 34495] Selecting objects in Blender 2.56 slow with gallium r600 driver

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=34495

--- Comment #44 from Pierre-Eric Pelloux-Prayer <pelloux at gmail.com> 2011-07-12 02:31:41 PDT ---
(In reply to comment #43)
> I'm not sure what's supposed to be the behaviour of changing the FBO while in
> GL_SELECT mode, but since GL_SELECT doesn't actually write to the FBO, I would
> assume it would be OK to change FboSave when changing the current FBO while
> GL_SELECT is active, no?

Yes, I'll add something like this.

> After that we may need to do some voodoo math to the projection matrix to use
> the user defined scissor during the render in GL_SELECT. We will also need to
> intercept scissor changes when in select mode to change the saved scissor and
> the projection matrix instead of modifying the actual scissor used for
> rendering which needs to be disabled.

According to this : http://glprogramming.com/red/chapter13.html 
"In both feedback and selection modes, information on objects is returned prior
to any fragment tests. Thus, objects that would not be drawn due to failure of
the scissor, alpha, depth, or stencil tests may still have their data processed
and returned in both feedback and selection modes."

So scissor has no effect in GL_SELECT mode, so the current patch looks correct
(except it should disable alpha and stencil tests too)

>  Maybe we could add a switch to change from old behaviour
> to this new behaviour to enable users to test it first before being enabled by
> default...

Good idea, will do.

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