Hi, I''ve been making a 3d-engine for a while and I have some questions: I would like to include a point/plane intersection test in my engine, but the formula is not quite clear to me...The one I''ve seen is: dist=A.x+B.y+C.z and I wonder wether the A,B,C values are the plane''s normals or if they mean point1,point2 and point3? If so, I guess the x,y,z belong to those points, right? Or, if the A,B,C are the normals, then are the .x,.y,.z meaning *x (of point to test),*y and *z??? Please help me! My other question is if most people writing 3d-engines in OGL use the translate/rotate functions of OGL, and at the same time stores the heading/pitch... x,y,z values of each object somewhere else or if they use their own rutines for everything, thus losing the ability of hardware T&L?

The distance between a point and a plane is computed like this

dist = DotProduct(P-Q, N)

where P is the point of interest, Q is a point on the plane and N is the normal of the plane

The DotProduct is computed like this

DotProduct(U,V) = U.x*V.x + U.y*V.y + U.z*V.z

For your question about dist=A.x+B.y+C.z, my guess is that it should say dist=a*x+b*y+c*z where (a,b,c) is the normal.

You should definitely try to use translate/rotate functions of OGL as much as possible. I hope that most people do this otherwise they miss the optimizations in the drivers and hardware TnL.