Study On Modeling And Real-time Rendering Of Snow Scene

Real-time rendering of nature scene is a challenging topic in research of computer graphics. Meteorological scenes such as wind, rain, fog, haze, snow, sandstorm, etc are highly related to the people’s daily life. Modeling and rendering of snow scene with high realism has wide applications in the areas such as virtual reality, military drill, snowy disaster’s prevention and rescue, film special effects and game design, etc. In this thesis, the main research work is related with modeling and real-time rendering of snow scene. The following two items are the key contents of this thesis:1) Current methods cannot simultaneously simulate both the snow accumulation and falling effects for large-scale dynamic snow scenes. To solve this problem, we propose a new method of modeling and real-time rendering of snow scene. To simulate the accumulation of snowflakes on different objects in the scene precisely, we present an adaptive occlusion map for the falling snowflakes, with respect to the object distribution within the current view frustum. The occlusion map will be updated in real-time allowing dynamic objects to be included in the scene. To sim-ulate the huge amount of dynamically falling snow flakes, we adopt a view-dependent particles grouping technique to reduce the amount of the snowflakes, meantime move the view transform and evolution of snow particle system into GPU for acceleration. To enhance the realism of falling snowflake, we adopt a dynamic texture sequence of multi-rotary snowflake. Besides, a hybrid ap-proach of geometry and texture is employed to render the distant view of large-scale snow scenes with less computation. Based on the above approaches, we successfully implemented the real-time walkthrough of large-scale snow scenes including both urban and suburb circumstances, and generate the beautiful winter view such as heavy snow accumulation on the tree branches and the covers of cars, etc.2) Snow avalanche is a natural phenomenon that typically occurs in mountainous terrain, it is a catastrophic phenomenon for winter sports enthusiasts like skaters. But in Computer Graph-ics area, there are rarely works about snow avalanches. We propose a new method based on CFD(Computational Fluid Dynamics) to real-time simulate this phenomenon. This method is ran under the general GPU framework of SPH (Smoothed Particle Hydrodynamic). Because of phys- ical mechanism of snow avalanches, we use Non-Newtonian Fluids Model to describe the motion of the avalanche, considering the rheological behavior of snow avalanche, Cross Model(a type of rheological function) is used to simulate the time-variant characteristic of viscous force. To keep stability of snow avalanche,we use the XSPH technique (X factor correction of SPH). Besides, Using the technology of GPGPU in High-end graphics display card, we successfully implemented the real-time snow avalanches simulation.At the end of this thesis we conclude our work, and presents some limits which can be studied in the future.