Research Of Soft Shadow Algorithm Based On GPGPU

In virtual scene, shadow plays a crucial role in the realism of scenes and the immersion of users, and is an indispensable part to simulate the real world. However, it is often very time-consuming for accurate rendering of shadow, so that the real-time rendering of shadow is affected. Therefore, how to harmonize the problem of the shadow realism and real-time rendering, under the condition without affecting the realism improving the real-time rendering, or under the condition without affecting the real-time rendering enhancing the shadow realism, is still the key point of the shadow research in virtual scene.In recent years, with the GPU processing ability continuously increasing, the GPU applications extend from the graphics processing to the GPU general computing, many data handled by CPU can be redesigned to be processed by GPU now, the GPU powerful computing and parallel processing ability can be used to improve the efficiency. This provides a good solution for drawing the shadow with high real-time rendering and strong realism. Aiming at the above problems, this paper proposes a soft shadow generation algorithm based on GPGPU, combined with the GPU general computing technology DirectCompute, the main work as follows are be done:Firstly, this paper studies the interrelated technologies of shadow rendering, analyses the common shadow generation algorithms in detail, analyses and summarizes their advantages and disadvantages, and especially has a research on the soft shadow generation methods based on image-space, providing a strong theoretical foundation for this paper.Secondly, aiming at the realistic need of shadow rendering, on the basis of the PCSS algorithm,this paper puts forward a soft shadow generation algorithm based on GPGPU. It samples shadow map by poisson disk pattern, uses depth gradient to deal with the phenomenon of self-shadowing, uses the VSM algorithm to filter the shadow, and uses the summed area table to filter the shadow map dynamically, improving the shadow quality and rendering efficiency in a certain extent. Finally, aiming at the real-time need of shadow rendering, this paper gives a detailed analysis of the DirectCompute, summarizes the optimization strategies of using GPU for general purpose computing, proposes to speed up the implementation of the proposed algorithm reasonably with GPU, gives the detailed design process, and analyses the result. The result shows that the proposed method not only enhances the shadow realism of the virtual scene, but also improves the real-time shadow rendering, which is very suitable for soft shadow rendering of the virtual scene.