Keith Whitwell wrote: > On Mon, 2010-01-11 at 07:39 -0800, Corbin Simpson wrote: >> Pardon the subject pun, it was totally necessary at this early hour. :3 >> >> If the scissor test is enabled, and the scissors obscure the entire >> framebuffer, should drawing calls still be run?
If the scissor box size == the framebuffer size, it's as if the scissor test is not turned on. Recall that the scissor box discards what's _outside_ the rect. If the scissor box size is 0 by 0 pixels, then all drawing could be no-op'd. But I think that's a very rare case. >> Talking on IRC, it >> seems like there's a valid use-case for performance testing, and I'm >> of the mind that anybody that deliberately sets up the pipeline and >> scissor that way probably intended for it. > > I can't think of any application-visible side-effects which would affect > the correctness of either choice. > >> I just want a clarification so I know whether I should revert >> bfcafbe15dc, and also I wanted to document it. > > There are probably interactions with multiple-sized framebuffer > attachments that will make this test harder -- given the different > framebuffer sizes, it probably becomes the viewport rectangle that you > want to test against, if your hardware supports different-sized MRTs. > > Unfortunately it's a bit of a pain to extract the viewport rectangle in > current Gallium as we've got it encoded as a transformation rather than > a box. Just FYI, if the scissor rect is 0 by 0 (effectively clipping everything) we'd still need to do "drawing" for selection and feedback mode (so we couldn't totally short-circuit drawing in the state tracker, if that's where you wanted to do this). Plus, when we have vertex transform feedback, we'd still have to draw things regardless of the scissor state. -Brian ------------------------------------------------------------------------------ This SF.Net email is sponsored by the Verizon Developer Community Take advantage of Verizon's best-in-class app development support A streamlined, 14 day to market process makes app distribution fast and easy Join now and get one step closer to millions of Verizon customers http://p.sf.net/sfu/verizon-dev2dev _______________________________________________ Mesa3d-dev mailing list Mesa3d-dev@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/mesa3d-dev
