why not, here's a spline surface demo with about 5 different interpolation algorithms implemented and normals calculated by definition (cross product of partial derivatives) and by finite difference approximations.
This was done as a project for a Numerical Methods course so graphics were not the main focus. As a result there is no texturing and lighting and rendering is a little ugly in places.
Uses C++, GLUT, and OpenGL.
Controlls are self explanitory in the Right Click Menu
*note: this was developed origionally for SunOS. i'm attatching an exe that runs fine for me on WinXP. No source for now as this project may serve as a basis for another school project.
If anyone has questions or comments about the math behind spline surface interpolation just post, id be happy to answer. general comments always appreciated (although im already aware of the obvious uglies in the program)
btw: i know its not a game but this is more or less the Graphics forum as well as Game forum