Frustum Culling

 http://local.wasp.uwa.edu.au/~pbourke/projection/frustum/

In order to determine whether part of a primitive is inside the frustum it is necessary to check that every vertex in the primitive is outside the volume. To determine this, compute the vertices of each plane making up the frustum. Each plane can be written in the form, Ax + By + Cz + D = 0. The constants A,B,C,D can be calculated from any three points on the planes (since all four points are coplanar) say (x₁,y₁,z₁), (x₂,y₂,z₂), and (x₃,y₃,z₃) as follows:

A = y₁ (z₂ - z₃) + y₂ (z₃ - z₁) + y₃ (z₁> - z₂)
B = z₁ (x₂ - x₃) + z₂ (x₃ - x₁) + z₃ (x₁ - x₂)
C = x₁ (y₂ - y₃) + x₂ (y₃ - y₁) + x₃ (y₁ - y₂)
- D = x₁ (y₂ z₃ - y₃ z₂) + x2 (y₃ z₁ - y₁ z₃) + x3 (y₁ z₂ - y₂ z₁)

In order to test whether a point (x,y,z) is on the left or right of the plane compute Ax + By + Cz + D. If the result is greater than zero then the point is on the same side as the normal (A,B,C), if less than zero then it's on the opposite side, if zero then it lies on the plane.

http://www.lighthouse3d.com/opengl/viewfrustum/index.php?intro

http://www.flipcode.com/archives/Frustum_Culling.shtml

http://www.cescg.org/CESCG-2002/DSykoraJJelinek/index.html

http://www2.ravensoft.com/users/ggribb/plane%20extraction.pdf

http://www.crownandcutlass.com/features/technicaldetails/frustum.html