Compute length of rational bezier
Outline rational_curve_arc_length
rational_curve_arc_length and unit tests
rational_surface_closest_point, rational_curve_closest_point, divide_curve_equally_by_arc_length, divide_curve_by_arc_length
Unit tests for _at_arc_length and _by_arc_length methods
Fixes for rational_curve_closest_point
Curve degree elevate.
Testing and fixing.