Feature design on deformation of freeform surfaces using range control

This research is to develop a freeform surface design method which uses a feature-based design approach to process surface deformation. Using this method, called range control, a user modifies or changes the position of a characteristic control point of the control polyhedron for a Bspline surface, and regional surface deformation is then carried out through automatic displacements of a group of control points surrounding the characteristic point. The position changes of the group of control points are the interpolations of the maximum movement of the characteristic point related to a feature dimension and zero movements of some fixed points on the designated boundary. In this range control surface deformation method, three interpolating approaches are proposed to smooth out the changes between the characteristic vertex and fixed vertices. they are based on the linear interpolation under the consideration of index, distance and angle distributions. The ideas are implemented on a feature-based designing system for shoe lasts. Design examples are given to show that the range control method is simple, fast and practically applicable for shape deformation of freeform surfaces.