Area Subdivision Method:

In this method, the viewport is verified for clear decisions on the polygons situated in it, in regard to their overlap and visibility to the viewer.

For the visibility of a polygon in the viewport, its x- and y-extents are compared with the horizontal and vertical spans of the viewport, and classified as one of the following, with respect to Figure, in which, the x-y extents of the polygon are marked by its bounding rectangle :

1. Surrounding

2. Contained

3. Disjoint

4. Overlapping or Intersecting