03/13/2003
15-462 Graphics I
18
Boundary Cases
•Boundaries
and special cases require care
–Cracks
between polygons
–Parity
bugs: fill to infinity
•Intersections
on pixel: set at beginning, not end
•Shared
vertices: count ymin for
parity, not ymax
•Horizontal
edges: don’t change parity
set pixel
don’t
set pixel
parity
change
no parity
change