"Alexander G. M. Smith" <agmsmith@xxxxxxxxxx> wrote: > That sort of rounding problem shows up as gaps between polygons in 3D > systems, since the > edges are usually placed using a line drawing algorithm. You want the line > to be exactly the same, > no matter what the order of the endpoints is. It's a bit trickier since the > vertices are floating point > numbers until the very last transformation step. Takes a lot of care to get > it "pixel perfect". it does take a lot of care indeed. just as a sidenote in this regard, if you care about sub-pixel precision then your vertices would remain fp (or fixed-point, whatever you use) even past the last transformation (i assume you mean the NDC-to-window transform), until the very last moment of putting your pixels on the screen. Michael Phipps <mphipps1@xxxxxxxxxxxxxxxx> wrote: > Yikes. I bet that would be no fun to debug down the road. :-/ as with any task which requires sound math, doing your numerical analysis in advance and with good care is essential. what differentiates computer graphics from the rest computational areas of intense math, though, is that your errors usually pop up right in your face ;)) you just need to have the eye for those. -blu