We propose new connectivity editing operations for quadrilateral meshes with the unique ability to explicitly control the location, orientation, type, and number of the irregular vertices (valence not equal to four) in the mesh while preserving sharp edges. We provide theoretical analysis on what editing operations are possible and impossible and introduce threefundamentaloperations to move and re-orient a pair of irregular vertices. We argue that our editing operations are fundamental, because they only change the quad mesh in the smallest possible region and involve the fewest irregular vertices (i.e., two). The irregular vertex movement operations are supplemented by operations for the splitting, merging, canceling, and aligning of irregular vertices. We explain how the proposed high-level operations are realized through graph-level editing operations such as quad collapses, edge flips, and edge splits. The utility of these mesh editing operations are demonstrated by improving the connectivity of quad meshes generated from state-of-art quadrangulation techniques.

We show how to model geometric patterns on surfaces. We build on the concept of shape grammars to allow the grammars to be guided by a vector or tensor field. Our approach affords greater artistic freedom in design and enables the use of grammars to create patterns on manifold surfaces. We show several application examples in visualization, anisotropic tiling of mosaics, and geometry synthesis on surfaces. In contrast to previous work, we can create patterns that adapt to the underlying surface rather than distorting the geometry with a texture parameterization. Additionally, we are the first to model patterns with a global structure thanks to the ability to derive field-guided shape grammars on surfaces.

We describe an interactive editing framework that provides control over the type, location, and number of irregular vertices in a triangle mesh. We first provide a theoretical analysis to identify the simplest possible operations for editing irregular vertices and then introduce a hierarchy of editing operations to control the type, location, and number of irregular vertices. We demonstrate the power of our editing framework with an example application in pattern design on surfaces.