Adaptive Tessellation of Subdivision Surfaces in OpenSG

For a variety of reasons subdivision surfaces have developed into a prominent member of the family of freeform shapes. Based on a standard polygonal mesh modeller can build various kinds of shapes using an arbitrary topology and special geometrical features like creases. However, the interactive display of subdivision surfaces in current scenegraph systems based on static levels of detail is unpractical, because of the exponentially increasing number of polygons during the subdivision steps. Therefore, an adaptive algorithm choosing only the necessary quads and triangles is required to obtain high-quality images at high frame rates. In this paper we present a rendering algorithm which dynamically adapts to static surface properties like curvature as well as to view-dependent properties like silhouette location and projection size. Without modifying the basis mesh, the method works patchwise and tesselates each patch recursively using a new data structure, called slate. Besides these geometric properties the algorithm can also adapt to the graphics load in order to achieve a desired frame rate in the scenegraph system OpenSG.