Study On Level-of-detail For Geometry, Motion And Behavior Of Real-time Virtual Environments

The application of LOD technology in Virtual Reality is more and more widely, by which represents non-important and important geometric objects in virtual environment with different level of details to reduce the computation cost of real-time rendering. The geometric LOD algorithms have already been researched for many years , then the research on motion LOD and behavior LOD becomes a new research direction of the virtual reality technology, and it focus on representing the animation characters with different level of details of motion and behavior.This paper introduces the LOD simplification techniques at geometric level of the virtual environment and analyzes the represents of animation characters at motion level. The technology of LOD simplification at motion level, such as motion edit, skeleton simplify, Joint Posture Clustering, is discussed, We present the methods extracting motion characteristics to mark motion capture data at motion level, and select different simplify methods based on these marks when rendering. By this way, many simplifying works at motion level are put in the pre-process stage. The described approach accelerates the rendering speed in real-time. At behavior level, the basic behavior models and complex behavior models are proposed; A LOD simplify framework in virtual environment based on the geometric, motion, behavior is presented, by which can create virtual character behavior models and implement the LOD simplify at three levels.This paper uses motion capture data to driven skeleton animation. The discrete motion LOD simplify method is experimented by extending BVH file, then the continuous motion LOD simplify method is controlled by frame distance. Above methods are applied to dance square application, and achieves better visual effects while reducing rendering time.The experimental results show that it can retain main features of character animation and improve rending speed by LOD technology that represent animation characters with different level of details of geometry, motion and behavior. The proposed method is effective to increase the number of characters in virtual environment at a constant frame rate.