Algorithm:

A divide and conquer algorithm

Warnock (PolyList PL, ViewPort VP)

If (PL simple in VP)

then Draw PL in VP, else

Split VP vertically and horizontally into VP1, VP2, VP3, VP4

Warnock (PL in VP1, VP1) Warnock (PL in VP2, VP2)

Warnock (PL in VP3, VP3) Warnock (PL in VP4, VP4) End

What does "simple" mean?

No more than one polygon in viewport

 Scan changed polygon clipped to viewport

Viewport only 1 pixel in size

Shade pixel depend on closest polygon in the pixel

Figure: Warnock's Algorithm

Runtime : O (p x n)

p : number of pixels

n : number of polygons.