----- Original Message ----- > Do we really need the lower_left_origin state? I think I can't > implement it for radeon and it's the kind of stuff that should be > taken care of by the state tracker anyway.
My understanding is that hardware had switches for this sort of thing. It's really hard to provide fully-conforming rasterization for opengl, dx9 & dx10 without it. If your hardware allows to put a negative pitch on rendertargets, then that should also do it. If you know what is the hardware's sub-pixel rasterization resolution, then adding a vertical bias equal to that amount, depending on this state, would give a very close approximation. (This would get the top/bottom edges right, at expense of small inaccuracies on non-horizontal edges) > Isn't it sufficient to just > set a viewport which is upside down, like we do now? I'm not aware of rasterization top-left rule being affected by the viewport flipping. Do both ./bin/triangle-rasterization -auto ./bin/triangle-rasterization -use_fbo -auto currently work for you? If drivers don't provide this state, the only way to workaround it I know would be to store textures (or drawables?) up-side down, and flip them on gl(Get)TexImage & friends. This would be like using a cannon to shoot a fly (a lot of work and a lot of overheads for a small correctness detail). I think the drivers are better equipped to handle this. And you always have the option of merely ignoring this state. Top-left rule correct rasterization has, after all, been ignored till date, and nobody cared. For the record, my motivation here is simple: llvmpipe gets the right behavior on GL drawables, and fails on GL FBOs & D3D 9/10. I want to get the right behavior on D3D 9/10 without causing regressions on GL drawables. BTW, I'd imagine that if hardware rasterizer behavior is hardcoded to anything, it would be to D3D 9/10 behavior. That is, they would get GL FBO right, but drawables wrong. Jose _______________________________________________ mesa-dev mailing list mesa-dev@lists.freedesktop.org http://lists.freedesktop.org/mailman/listinfo/mesa-dev
