Area Subdivision Method
In this method, the viewport is examined 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 within 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 3.13, in which, the x-y extents of the polygon are marked by its bounding rectangle :
(a) Surrounding
(b) Contained
(c) Disjoint
(d) Overlapping or Intersecting