Via the new concepts of sunny facets,shady facets and flat projective facets of a convex polytope to an outer point and two shield lemmas,it is proved that any n-polytope in Rn can be dissected into a finite union of n-simplices with the vertices coincide with the original polytope and no pair of small simplices has an interior point in common.

Improvement of real-time planar shadow algorithm and its implementation;

Introduces the principle of planar shadow technology using computer graphics, the solve method about the problem of shadow with polygon offset and stencil buffer technology for processing complicated real time 3D drawing are also introduced.

The settlement on south faced slope is usually more than that on north faced slope,as indicated that the thawing of permafrost under south faced slope is acuter.