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.