Containment Test -  visible surface detection

Test: That is Containment test: it can be either comprised (contained) or surrounding polygon, if intersection test fails. Therefore we perform the containment test for this type of test we have the subsequent three cases, demonstrated in the figures (a),(b) and also (c).

a)   P1 contains P2. b)   P2 contains P1.

c)   P1 and P2 are disjoint.

                                         Figure (a): P1 contained P2          (b) P2 contained P1           (c) P1and P2 are disjoint

Case a: Confirm a vertex point of P2 lies inside of P1. Whether the result is true, P2 is entirely within of P1.

Case b: Verify where P2 contains a vertex point of P1, if the consequence of case a is not true. If the result is true, then P2 comprises P1.

Case c: If both case-a and case-b as containment test such are failed then we decided to disjoint P1 and P2.

For a known screen area, we remain a PVPL that is potentially visible polygons list, those in categories 1, 2 and 3. Disjoint polygons are certainly not visible. Also, notice that on subdivision of a screen region, disjoint and surrounding polygons keep in surrounding and disjoint polygons of the newly formed regions. Thus, only intersecting and contained polygons necessitate to be reclassified.