Real-time Atmospheric Scattering Rendering Algorithm Based On GPU

Atmospheric scattering is a very important and common physical phenomenon in nature,it makes the sky seems blue in the daytime,and seems yellow in the evening;It makes the near scene seems clear,and the distant scene seems dim.Atmospheric scattering is also the principle of a lot of optical phenomenon,such as volume light.It plays an important role in the influence of people's visual sense.In computer graphics,the traditional drawing method of the sky is sky box or sky map.This method is simple and fast,but it cannot simulate the dynamic lighting effects of real-time climate change in different time.As the improvement of computer performance especially the GPU graphics rendering ability,atmospheric scattering effect based on real physical simulating in the virtual scene gradually become possible.Therefore,people have summarized a complete scattering integral equation,which can calculate the light radiation intensity changes in air transport accurately.However,due to the complication of the integral calculation,even in the modern GPU is hard to hold smooth real-time rendering.Under such a background,this thesis implements a real-time atmospheric scattering rendering optimization algorithm based on GPU computation.We calculate the scattering integral by ray-marching based on the real physical modeling of the atmosphere,and use a pre-computed lookup table to simplify the scattering integral calculation,use epipolar sampling to reduce the number of sample points,using a 1D min/max binary tree structure to accelerate the visible factor judgment.As ensuring a good rendering result,we significantly improve the rendering efficiency.This thesis first expounds the algorithm of the air physical model,and detailed description of the derivation process of the scattering integral,then,we describe the algorithm how to optimize the calculation step by step,and shows the implementation details on the GPU.Finally,we write a test program for rendering effect,and made a comparison with the traditional algorithm,our algorithm can get a satisfying result,both on the rendering result and rendering efficiency.