On Tue, Sep 15, 2015 at 7:12 PM, Ilia Mirkin <imir...@alum.mit.edu> wrote: > On Tue, Sep 15, 2015 at 1:09 PM, Erik Faye-Lund <kusmab...@gmail.com> wrote: >> On Tue, Sep 15, 2015 at 6:49 PM, Ilia Mirkin <imir...@alum.mit.edu> wrote: >>> However having a piglit test that covers this would be neat... I guess >>> you could clip a pixel in half and make sure that the resolved result >>> is some in-between color? Lots of implementation-dependent stuff going >>> on in there though. >> >> I think this would simply be a matter of drawing a white triangle on a >> black background both with clipping and pre-clipped, and verify that >> the result is the same. Perhaps even using a few differently sub-pixel >> jittered triangles. > > Right, but sample positions are implementation-defined. Although I > guess you could retrieve those positions and pre-clip yourself...
No need to do that, I think. Clipping happens earlier in the OpenGL pipeline than rasterization, so a user-clipped triangle and a pre-clipped triangle should produce exactly the same result. There is of course a chance of some variance in the calculations, though. So perhaps it'd be better to do a user-clipped triangle vs a near-plane clipped triangle one. Those are defined to be clipped in the same pipeline-stage, and should yield the same result. > However the resolve is also implementation-defined I think, so there's > no good way to know what the resulting color would be. However you > could ensure that it was neither white nor black. Yeah, that's why I'm suggesting comparing two renderings that should give the same result instead. _______________________________________________ mesa-dev mailing list mesa-dev@lists.freedesktop.org http://lists.freedesktop.org/mailman/listinfo/mesa-dev