Chen Rabiner wrote: > Hello guys, > > My name is Chen, and I’m working on linux-opengl compatibility tests for > embedded design. I am using MESA as reference code. > > As far as i understand opengl require to sample at pixel centers (e.g. > (0.5,0.5) (1.5, 0,5) and so on...) and check if that exact point lies inside > a triangle. > > Mesa swrast has had TRIANGLE_WALK_DOUBLE in config.h which allowed working > with double precision numbers instead of fixed point and snapping > coordinates . when i turn it on and off i get different results of the final > picture.
I haven't tried the TRIANGLE_WALK_DOUBLE code in ages and don't know what shape it's in. > my questions are > 1. Do both modes (e.g. double and fixed) test if a sampled pixel center is > inside the triangle, from the calculation i'm not sure. Yes. > 2. what is Mesa swrast tie breaker rule when a sampled point lies on a > shared edge that is shared by two triangles? I believe that if edge exactly hits the pixel center then for left/bottom edges the pixel is considered "in" and for right/top edges it's considered "out". > 3. my guess is that fixed point snaps somewhere around the pixel center and > not the exact center. Fixed-point snapping could exactly hit a pixel center. > I know that Mesa doesnt exactly samples, it does some complicated setup and > than scanline using that setup but if someone can describe in words how this > correspands to sampling i would be most grateful. By "samples" do you mean point sampling or multisampling or something else? The OpenGL spec explains point sampling, if that's what you're after. -Brian ------------------------------------------------------------------------------ Apps built with the Adobe(R) Flex(R) framework and Flex Builder(TM) are powering Web 2.0 with engaging, cross-platform capabilities. Quickly and easily build your RIAs with Flex Builder, the Eclipse(TM)based development software that enables intelligent coding and step-through debugging. Download the free 60 day trial. http://p.sf.net/sfu/www-adobe-com _______________________________________________ Mesa3d-dev mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/mesa3d-dev
