NURBS control points

Hi dear friends,
I’ve been working with NURBS cuve for almost two week but I cannot find a soution to the following two topics:

1)when I try to add control points to my curve(of course after widening the knot set)it comes out in an empty window…no curve appears on the screen;

2)according to a NURBS equation I should deal with WEIGHTS;indeed they’re used to modify the curve shape.BUT,where do WEIGHTS appear in GLU function gluNurbsCurve?Are they tied to the fourth coordinate (x,y,z,w) when w<>1?

thanks for any answer


Maybe I have an answer to your first question.
Your number of control points added to a single curve is limited by the maximum equation order supported by your OpenGL implementation.
You can determine the order with glGetInteger(GL_MAX_EVAL_ORDER) (f.e. I almost get a maximum order of 8).
If your equation order is higher, OpenGL produces an error and no curve is drawn.