Abstract
In CG animation, the method for modeling of CG characters such as humans or animals is important. If these shapes are represented by parametric surfaces, such as Bezier, B-spline, or NURBS surfaces, complex procedures are required to make adjacent surfaces connect smoothly. To solve this problem, instead of parametric surfaces, subdivision surfaces are often used to represent shapes. However, how best to fulfill efficient modeling intended by designers is still problematic. Another method is proposed to model complex freeform surface shape, with which the boundary curves of a surface are specified to create a curved mesh and mesh area within the boundary is interpolated with Gregory patches. This kind of modeling method enables to modify a curved mesh directly with intuition so as to achieve a desired shape. In this paper, to take an advantage of the features of both Catmull-Clark subdivision surface and Gregory patch, we propose a local modification method that generates a curved mesh from a polygon mesh with the same topology using a Catmull-Clark subdivision surface, modifies the generated curved mesh directly and applies the modified curved mesh shape to the polygon mesh. One of the characteristics of our method is that modification of some vertices or edges affects only their adjacent surfaces. Also, the surfaces within a specified range can be modified freely with maintaining the continuity between the surfaces and their adjacent surfaces outside the specified area. Applying modification of a curved mesh to a polygon mesh enables local modification or intuitive modification that are rather difficult to perform for a polygon mesh.
