Open-source, cross-platform NURBS

Curve by point interpolation
Closest point to a curve
Divide a curve by arc length
Curve-curve intersection
Split a curve
Cylindrical surface
Extruded surface
Revolved surface
Lofted surface
Adaptive surface tessellation
Mesh-mesh intersection
Mesh slicing
NURBS Surface
Surface boundary curves
Closest point to a surface
Surface Isocurves
Surface-surface intersection
Splitting a surface
Swept surface