NURBS streams

Deformable objects are important in modeling clothing, facial expressions, animal characters and other soft objects. However, they are rarely used in distributed virtual environments. This is because both the transmission and the tessellation of deformable objects are too time-consuming to run in real time. Part of the problem can be solved by our earlier (1997, 1999) method on the real-time rendering of deformable NURBS (non-uniform rational B-spline) surfaces. In this paper, we present a technique to organize the data structures that are used to store the pre-computed polygon models and the deformation coefficients in supporting the rendering of deformable NURBS surfaces from a hierarchical form into a linear form, called NURBS streams. The NURBS streams not only support the progressive transmission and rendering of deformable NURBS surfaces, but also simplify the software and hardware implementation of the rendering method. To further speed up the rendering of these NURBS streams, we also introduce the idea of a virtual rendering list to keep track of incremental node changes between successive frames