GPU-based smooth free-form deformation with sharp feature awareness

Abstract

In an accurate free-form deformation of a polygonal object, only the linear geometry, e.g., triangles or planar polygons, is deformed as triangular Bézier patches or trimmed tensor product Bézier patches; the related normal field is not considered. Thus, the geometry appearance and shading of the deformed object are typically not smooth. In this paper, both the linear geometry and normal of a polygonal object are simultaneously considered in the framework of accurate free-form deformation. First, each triangle and its normal field are deformed as two cubic triangular Bézier patches. Then, the curved geometry corresponding to the deformed triangles is locally adjusted to tone the smoothness of the geometry appearance according to the deformed normal field. The deformed normal field is adjusted accordingly. As a result, a smooth free-form deformation with visually plausible smooth geometry and shading is obtained. Furthermore, the sharp features in the polygonal object can be preserved. Because the curved geometry and normal field adjustments are local operations, all of the above computations can be performed in parallel on a GPU. The experimental results show that the method can deform a complex polygonal object as a smooth object in real time while preserving sharp features.