In this method the following tests are performed: Considering A and B are two polygons

1) Z extents of A and B do not overlap.

2) Y extents of A and B do not overlap.

3) X extents of A and B do not overlap.

4) A is lying at the opposite side of B from the view.

5) B is lying at the same side of B from the view.

6) Projections of A and B do not overlap.

Depth Sort or Painter’s Algorithm:

1) Sort given polygons in order of decreasing depth.

2) Determine polygons in polygon list whose Z extents overlap that of A.

3) Perform Tests 2 to 6 for each B.

4) If B passes test, scan convert A.

5) If tests fail for B, swap A and B in list and make a note that B is swapped. If B has already been swapped use plane congaing A to divide B in to two polygons B1 and B2. Replace B with B1 and B2. Repeat Step 3.

## Leave a Reply