03/13/2003
15-462 Graphics I
16
Concave Polygons: Winding Rule
•Approach
2: winding rule
•Orient
the lines in polygon
•For
each scan line
–Winding
number = right-hdd – left-hdd
crossings
–Interior
if winding number non-zero
•Different
only for self-intersecting polygons
Even-odd rule
2
1
1
1
1
1
Winding rule