how can I calculate a tangent (in 3d usually a plane) through a given point on a surface using VTK? I already tried the following:
- Use an implicit dataset to transform polydata to an implicit surface representation and then
- calculate the gradient at the given point using the method FunctionGradient(…).
However, the gradient I received seems to be wrong (which is (0, 0, 1)).
Any help would be appreciated.