Direct highlight line modification on nurbs surfaces Original Research Article

Reflection characteristics of surfaces, as visualized by highlight lines, are important design objectives in automotive styling. A method is presented that allows the direct modification of a highlight line on a NURBS surface. The algorithm presented will automatically adjust the control points of the NURBS surface resulting in a modified surface shape that produces the desired highlight line. A system of nonlinear equations is developed that expresses the relationship between NURBS control points and reference points on the highlight line. The inverse problem is solved through linearization by a first-order Taylor expansion. In addition, a shape control mechanism is introduced that distributes control point changes over the surface in a coherent and predictable way. With this mechanism, the user is able to interactively control the locality, or extent, of the surface modification while maintaining the desirable highlight line modification.