Was overdoing it previously.
/* correct for top-left fill convention:
*/
- if (tri->dy12 < 0 || (tri->dy12 == 0 && tri->dx12 > 0)) tri->c1++;
- if (tri->dy23 < 0 || (tri->dy23 == 0 && tri->dx23 > 0)) tri->c2++;
- if (tri->dy31 < 0 || (tri->dy31 == 0 && tri->dx31 > 0)) tri->c3++;
+ if (tri->dy12 < 0 || (tri->dy12 == 0 && tri->dx12 > 0)) tri->c1 += 1.0/16.0f;
+ if (tri->dy23 < 0 || (tri->dy23 == 0 && tri->dx23 > 0)) tri->c2 += 1.0/16.0f;
+ if (tri->dy31 < 0 || (tri->dy31 == 0 && tri->dx31 > 0)) tri->c3 += 1.0/16.0f;
/* find trivial reject offsets for each edge for a single-pixel
* sized block. These will be scaled up at each recursive level to