Curvature Combs visualize the curvature of a Bezier curve in order to enable the designer to draw smoother curves.     See section 2.11 here: http://cagd.cs.byu.edu/~557/text/ch2.pdf   Often I find my self in position that I drew a curve but it just does not look smooth enough and I fiddle around until it looks smooth. Would be great to have some more clear feedback.