Suppose I have N random points in space. How to pull a NUBRS surface on them and calculate the volume under it?

They have nothing to do with OpenGL.

Instead of the using NURBS, canâ€™t you just find a convex hull of the points, and calculate the volume of the convex hull?

If the points or on a surface of the volume only, then you could use interpolation to calculate a nurb surface, but this is not available in OpenGL, you have to do the interpolation yourself or get a nurbs library with this support.

Mikael