<html> <head> <base href="https://bugs.freedesktop.org/" /> </head> <body> <div> <a class="bz_bug_link bz_status_NEW " title="NEW --- - [llvmpipe] Front/Backfaces do not cover the same pixels when rasterized" href="https://bugs.freedesktop.org/show_bug.cgi?id=78914#c6">Comment # 6</a> on <a class="bz_bug_link bz_status_NEW " title="NEW --- - [llvmpipe] Front/Backfaces do not cover the same pixels when rasterized" href="https://bugs.freedesktop.org/show_bug.cgi?id=78914">bug 78914</a> from <a class="email" href="mailto:sroland@vmware.com" title="Roland Scheidegger <sroland@vmware.com>"> Roland Scheidegger</a> <pre>Actually I think I know what's happening here. Our rasterizer can only handle counterclockwise triangles (so the edge function sign indicates if a fragment is inside or outside a plane and ultimately the tri). To make it work we rotate the triangle if the triangle is clockwise to make it counterclockwise (if backface culling is disabled). So far so good. But for correct fill rules (to get cases right where fragment centers are on edges) we also fix up the plane coefficients - and we do this based on the sign of the steepness of the plane function, but because we exchanged two vertices in case when we have front face culling instead of back face culling (so actual winding of the tri did not really change, we just treat it as if it would have changed) we get it wrong. Though this requires some further analysis, it is quite possible I made some mistake here, this is tricky to get right!</pre> </div> <hr> You are receiving this mail because: <ul> <li>You are the assignee for the bug.</li> </ul> </body> </html>