Simulation Of Underwater Scene Based On GPU

As a subsidiary project of"Virtual Taihu Lake"developed by some Supervising Department of Suzhou, the main task of this paper is to simulate underwater scenes of lake on personal computer.The complexity and fantastic optical effects of underwater scenes recently has attracted more and more attention to simulate. Most of papers only pay attention to one part of underwater scenes just as water surface or optical effect, etc. Because of limitation of study time, this thesis select 4 key parts of underwater scenes to simulate, ground surface, caustics, water grass, water surface, based on particular algorithm which takes account of balance of rendering effects and rendering efficiency.This thesis proposes a method of fast parallax occlusion mapping to simulate ground surface of underwater. Compares with traditional grid modeling method, it gets the subtle details and achieves complex effects which are hard to simulate for grid modeling method. Compares with other parallax occlusion mapping, it is of great higher rendering frame rate. For simulation of water, Gerstner wave function is used to modeling, environment map and normal map are used to render, which ensure complicated effects of water surface based on relatively low complexity of grid modeling. For simulation of caustics, this thesis use reverse light tracing which abandons lots of light not contribute to caustics. In the process of Snell law, the normal is computed by partial derivative of Gerstner wave function, which ensures consistency and synchronism between water wave and caustics. For modeling of water grass, B-spline curve is used to generate middle line of grass blade, other grid points is generated based on middle line. By means of different transformation of scale and rotation for one grass blade, other blades are produced, then the whole grass is generated. Perlin noise is applied to simulation of dynamic effect of grass. To decrease the amount of calculation of Perlin noise, only control points of middle line are implemented for Perlin noise to change line's form, therefore change the forms of grass blades in real-time. All those parts of underwater scene are processed through quadric exponential light attenuation.Modern GPU has great capability of parallax processing for computer graphics. The rendering of underwater scenes takes full advantage of GPU's hardware acceleration, which greatly reduce computation burden of CPU. The project achieves relatively well simulation effects and fluent frame rate, reaching the required standard of task.