Highlight lines for surface quality control and shape manipulation.

Abstract

Highlight lines are a new type of viewer-independent reflection lines for more effective and efficient surface quality assessment and shape manipulation. In this dissertation, the concept of the highlight line is introduced and extended into highlight bands and band boundary curves. Forms and properties of highlight lines are shown, and their application to surface quality evaluation are demonstrated. Two highlight band algorithms are presented, one utilizing a point-selecting approach and the other a polygon-partitioning mechanism. Both algorithms allow the real-time generation of color-coded highlight bands in response to various user interactions. Highlight line and highlight band boundary creation is formulated into a surface-plane intersection problem. This problem is solved numerically using an efficient traced contour-line approach, resulting in a robust algorithm with real-time response. Based on the implicit function theorem, a method is devised that enables the user to directly modify a highlight line in parametric space of a NURBS surface, and automatically adjusts the surface shape by computing the required changes in the control point positions. This method is then generalized to allow modification in both object and parametric space, simultaneously. Furthermore, an editable shape function is introduced that propagates control point changes over the domain and provides the user with flexible control over the character of the resulting surface geometry. The significance of this body of research is the introduction of an intuitive smoothness indicator, the highlight line, and the development of a method that allows the direct modification of this smoothness indicator. The direct highlight line modification requires the solution of a difficult inverse problem that automates the necessary surface adjustment in a single step. Compared with conventional methods where surface features are modified indirectly through the movement of control points, an iterative and time-consuming process, the new techniques presented in this dissertation are direct, create results with real-time response, and provide the user with significant flexibility in achieving design objectives.