ABSTRACT
The computation of contacts and entrances is the geometric computation. Geometric computation is different and difficult. Given block A and block B, there are two entrance possibilities:
Case1 A and B have no contact
A B∩ = φ (1)
Case2 A and B entered each other
A B∩ ≠ φ (2)
The definition of entrance block transfers the contacts of two blocks to the contacts of one block and one point.
