Research, Physics-based Real-time Computer Animation

Physically based computer animation is always a hot topic in computer graphics especially in the special effects industry for films and games. Physically based modeling is used to build precise movement model for objects using computer through exploring physical nature of natural phenomena in the real world, and then simulate object's movement more realistically. However, the complexity of the physical computation often leads to serious performance degradation, so it is necessary to investigate on the acceleration techniques. This paper aims to solve the problem by seeking for a tradeoff between the realistic effects and real time performance, to meet the needs from computer games.This paper focuses on the study in two aspects:1. An efficient and stable method to animate virtual cloth based on physical model is proposed. This thesis first analyse physical nature of cloth in real world, and then based on mass-spring model, propose a strategy of replacing spring by stick which could change length, to simulate the compression and bending phenomenon of cloth. In numerical method, we employ stable and fast verlet integration method to solve movement equation. Compared with other approach, our method has the advantage of accurate and realistic and cloth is more softly. Another important problem of cloth animation is how to handle the collision between cloth and othe rigid objects. To achieve real time effect, we develop a simple and efficient collision detection method based on specific rigid objects, and employ projection method to deal with collision. Furthermore, we provide an algorithm for an efficient avoidance of self-collison. Finally, we use GPU as a co-processor with CPU to accelerate the implementation of cloth animation system. We use the technology of vertex texture fetch on GPU to build cloth model, and the ability of general purpose computation on GPU to solve differential equation. Experimental results demonstrate that our method is satisfactory and is efficient enough to meet the demands of realistic and real time in computer game.2. Research on the technology of physically based water simulation. We first take advantages of the parallelism and the programmability of graphics hardware to accelerate the computation of two-dimensional wave equation. Then we could obtain the height map and build the water geometry model by vertex texture fetch on GPU. This algorithm avoids the communication between CPU and GPU, so it could improve the speed of simulation largely. Furthermore, in order to enhance visual sense, we also simulate several phenomena of water in real world: dynamically generate reflection texture and refraction texture according to the position of viewer, and then read texture data from pBuffer, to simulate the effect of reflection and refraction on water. Introduce a simple and efficient method to simulate caustic phenomena of water. Simulate realistically the movement trail of boat running on the water using texture mapping.