BSPLINE_INSERT_CONTROL_POINT inserts control points into a specified B-spline.
--->(BSPLINE_INSERT_CONTROL_POINT)----|B-spline|---+ | +-----------------------<----------------------+ | | +--------------------<---------------+ | | | +--+--|control line|----|new position|--+---->
BSPLINE_INSERT_CONTROL_POINT [pick new control point]