Given any four 3D points P1 P2 P3 P4 that are not coplanar i

Given any four 3D points P_1, P_2, P_3, P_4 that are not coplanar (i.e., the four points are not in the same plane), we can form a tetrahedron with four triangular faces in 3D. What is the maximum number of faces that can be removed by backface culling for arbitrary camera location? What is the minimum number of faces that can be removed by backface culling for arbitrary camera location? (4%) If we delete one of the triangular faces from the tetrahedron (i.e., three faces left), is it still valid to use backface culling on the 3D model? Please explain. (4%)

Solution

b) maximum 2 triangles

mimimum 1 traiangle

c) yes it\'ll be valid because we still can backface cull 1 triangle if we are at an angle where there are 2 triangle in backface.