Detection of collision and interference between 3D objects using normal vector

A new approach using a normal vector is given to detect collision and interference between 3D objects. By adding a surface normal vector to every vertex of polyhedron and curved entity surface, and getting intersection, the remainder length of the normal vector is calculated, and judgement is made whether two bodies are intersected. The approach can detect collision interference and calculate collision distance and directional distance in assembly planning. Furthermore, some measures are taken in order to increase algorithm efficiency and avoid any missing in detection.