Realistic Rendering Of Rain Scene For Large-scale Waters

The simulation of natural scene is widely used in virtual reality, movies’ special effects, military simulating, games and entertainment, etc. The rendering of rain scene for large-scale waters is one of the most challenging problems in computer graphics. This paper is based on the project of “Virtual Tai Lake” developed by some Surpervising Department of Suzhou. According to the rainfull characteristic of Tai lake area, this paper simulates realistic scene of large-scale waters in rainy day. The main task is to simulate water scene, the interaction effect of water and rain, and the scattering of the lights in rainy days.At first, we analyze the current simulation theory of water waves, and adopt the statistical wave model into water simulation. We realize the FFT algorithm with the multithread parallel computation in GPU, and optimize the simulation of water grid based on quad-lod model. By using the eye position as the center of the water, the infinite water is simulated.Then, this paper proposed a method of rendering of rain scene for large-scale water area. By introducing the improved wave equation into the fluctuation of water surface and the interaction of water and raindrop, and incorporating the periodicity and wind tendency of FFT, we establish the interactive fluctuation of water mathematical model in rainy days, and render the interactive height map. Through lighting rendering, we simulate the reflection effect and refraction effect and rain streaks. The method is efficient and achieves qualified refreshing frequency in real time scene rendering.At last, in order to simulate the phenomenon of light scattering in rainy days, this paper simulates the direct light, point light and spot light by using the method of separating physical parameters, and realizes the surface dizzy effect based on the BRDF theory. A method of simulating the appearance of anisotropy materials with BRDF is proposed, which adopts the physically based approach and uses 3D table to recomputed at interactive rates.By taking fully advantages of GPU during the simulation of the rain scene of Tai Lake,the result achieves the realistic effect and meets the requriment of real-time rendering. And we also build a complete scene system, which provides a friendly interface, and the interactive experience is enhanced.