NURBS calculation

Hi all!
I tried to write my own code to calculate Nurbs curves/surfaces, but it doesn’t work properly. If somebody already wrote same code, then send me, please, formulas you have used.

You have sources in the red book that can be donwloaded from gamedev. If you get the sources for GLUT is it also a lot of samples.

Of course, i have a lot of ready-to-use code written by programmers of SGI or others, such as gluNurbs interface etc. But i’m trying to write my own class (in c++) describing NURBS surfaces. I already wrote the code for 2d Nurbs curves, but i don’t understand, how i can produce the normal vectors to the surface, that i generate.
Do you have an experience in this area?

[This message has been edited by grimnir (edited 12-30-2000).]