I am trying to figure out how to get a smooth spline with more then 4 points using openGl evaluators. Anyone know how to do this?

The red book has good examples. But, you should probably read up on Bezier curves or NURB curves. Search Google.

Yes but the examples in the redbook and most others all use only 4 control points. I have been able to modify the code and get a spline with C2 continuity over 8 control points, but errors eventually come up. I am wondering about code to do any number of control points.

A basic bezier curve is defined by four points - start and end points and the tangents there. So to get a smooth curve through n points you create a bezier segment to cover each [n,n+1] and further specify that the tangent at point n is the same whether you’re arriving or leaving it(actually not the same but precisely opposite).

hope this is helpful.

Yes I understand that. I am able to make splines that can handle up to n vertices if I do all the math myself. However I can’t get openGL to do that. I am looking for code that can handle n vertices for any type of spline in openGL.

You could try looking at the source code from http://www.codeproject.com/useritems/CadSurf.asp . It uses bezier curves. It may or may not help you, but it looks like a decent app.