Fine level feature editing for subdivision surfaces

In many industrial design modeling scenarios the designer wishes to edit small feature lines-such as variable width and height creases--on otherwise smooth surface patches. When the path of such a feature does not align with an iso-parameter line or crosses patch boundaries it becomes increasingly difficult to maintain good editing semantics of the underlying surface. In this paper we describe an algorithm and implementation allowing the interactive creation and manipulation of fine scale feature curves on subdivision surfaces. In particular, our approach addresses the problem of defining the path of such feature curves independent of the location of surface iso-parameter lines and global patch boundaries. The feature lines are modeled as swept displacement curves with variable profiles, providing a rich toolbox of shapes. Furthermore, the hierarchical editing semantics of subdivision surface based representations carry through to our extended setting, ensuring "good" behavior of the feature lines under coarse scale surface edits.