I believe the fourth coordinate is present in homogenous coordinate

system.

e.g. [x y z w]

to obtain the actual 3D coordinate

if (fabs(w)>EPSILON) {

actualX = x/w;

actualY = y/w;

actualZ = z/w;

}

You may find more detail explaination and mathematics in

Computer Graphics : Principles and Pratice

Foley, vanDam, Feiner, Hughes ISBN 0-201-1210-7 (Addison Wesley)

> Hi!

> I've just been playing around wit hgeomview and I think I understand the

> bezier-splines for 2D and 3D. But what is the meaning of the fourth

> coordinate in 4D bezier splines? Do I see some kind of 3D section? Does

> anyone know a good reference to expain 4D bezier surfaces?

> Thx,

> Rudolf

> --

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