Spline Derivative

Does OpenCascade have function to create a derivatives of a 3D Surface (B-Spline / Bezier / NURBS)?

I want to analyse slope and slope changes on the surface

TIA

Rob Bachrach's picture

Look at GeomLProp_SLProps and BRepLProp_SLProps. I usually use the former, passing a surface obtained from a TopoDS_Face.

In either case, you supply the surface, the U,V parametric coordinates, the level of derivative you need, and the resolution of accuracy for the answer.

Make sure you use the IsTangentDefined and IsNormalDefined functions before looking at the actual result.