Quote:

*Originally posted by Shadow12345 *

To determine if a vertex is on in front or behind a plane use the following equation:

Ax + By + Cz + D = 0;

If it is 0, then the vertex substituted for the x,y,and z values are exactly on the plane, if it is greater than 0 then it is in front of the plane and it will give the distance from the plane, if it is negative it is behind the plane and it gives the distance from the plane.

This must be how John Carmack (and other developers) split polygons when doing binary space partitioning when a cutting plane intersects through a polygon (which is different from how you did it, Poly).

The A, B, and C values represent the normal vector of the plane, D represents any vertex that is known to be on the plane.

If any of that is inaccurate someone please explain why. Thanks.

Almost. Yeah, that's how it's done, but you are confused about D.