1. A drawing system, comprising: a computer system having a display and a pen input device having a pen stylus; the computer system having curve model generation software running thereon; and the curve model generation software responsive to a gesture made with the pen stylus selecting a point on a 3D vector curve and generating three orthographic planes that intersect with one another at the point selected on the vector curve and selecting the orthographic plane that is most perpendicular to a current view vector as a sketch plane.