The Rendering Of Renderman Specification Hierarchical Catmull-Clark Subdivision Surface

The rapid development of film special effects promotes the development of computer graphics technology. Computer graphics technology also affects the film and television industry deeply. Modeling and rendering is the most important computer graphics research topics,Many rendering algorithms have been researched,and rendering softwares may employ a number of different techniques to obtain a final image. But Renderman specification renderer has a great influence in the field of rendering. Realistic objects are represented by modeling in the film.Catmull-Clark subdivision surface supports arbitrary topology and can generate the smooth surface,which has the benefits of both NURBS surface and polygon,and it becomes an effective modeling method.Due to the low performance of early computers and time-consuming of subdivition algorithm,subdivision surfaces in the past were developed very slowly for many years.With the improvement of computer performance,subdivision theory and technology,Pixar applied the subdivision surface technology in the character animation. Pixar has now decided to open its subdivision patents and working codebase,and Renderman Specification subdivision surfaces will be more widely applied. Subdivision surface modeling has become one of modeling methods in the maya software. It is essential for rendering engine to support subdivision surface.The Renderman Specification Catmull-Clark subdivision surfaces specification was extended with local edits, creases, and other features, and formalized into a usable technique.There are some problems to realize rendering of the Renderman specification subdivision surface. These include supporting for hierarchical editing features, rendering performance in Reyes rendering process, accelerating structure and rendering performance issues in ray tracing rendering process. We discuss and resolve these issues.The main contributions of this paper:1.We proposed an adaptive algorithm based perspective.The irregular face is constantly subdivided,the regular face is transformed into bi-cubic B- spline surfaces,and the shading rate controls the subdivision of the bicubic B- spline surfaces and irregular surfaces. in this algorithm.2. We proposed a progressive subdivision algorithm based on the scene.In the ray-tracing rendering process, we improved acceleration structure and avoids unnecessary subdivision according to the influence of light in the scene.3. In the existing rendering system,we realized the representation and rendering of the Catmull-Clark subdivision surface. We proposed the effective solutions for the mesh data structure, the texture mapping computation, the bounding box border and the hierarchical editing features.Through the work of this paper, Render Wing has fully supported the Renderman specification hierarchical Catmull-Clark subdivision surfaces.We solved the texture mapping and bounding box problems. We tested our subdivision algorithm in the Reyes and ray tracing rendering process,the results show that our implementation has met the requirements of the commercial animation films for the Catmull-Clark hierarchical subdivision surface.