check if a surface is G1
Is there a method to know if a surface is G1 (or G2)?
For C1, etc. there is Geom_Surface::Continuity()
It would be nice to have even the G1-continuous intervals, along U and V.
I suppose I will have to
1) find the C1-continuous intervals with GeomAdaptor_Surface::UIntervals (and VIntervals)
2) at each discontinuity parameter, check the surface normals on the left and on the right of the isoparametric curve (in several points along it).