Real-time Rendering Under Dynamic Environment Lighting Using Spherical Harmonics

Virtual reality integrates computer graphics, human-computer interaction technology, sensor technology and artificial intelligence technology. It is the achievements of twentieth Century scientific and technological. Virtual reality has been widely applied in practical applications such as medicine, city construction, aerospace and electronic games. Augmented reality mix the virtual and real scene together to provide users with a more realistic visual effects. In recent years, virtual reality and augmented reality has become a hotspot of research and application.Realistic image rendering is an important task in virtual reality. The traditional graphics program only consider the point light, the direction light or a simple surface light. Although the traditional light source is simple and effective, but they draw the scene with limited reality. So the environment lighting is introduced to represent complex outdoor lighting surroundings, simulating lighting effects of real world. Environment lighting is collected directly from the real world, so scenes rendered under environment lighting show better realism than traditional lights. Rendering under environment lighting is rather complicated because all the light incident directions of the surface should be taken into account, which requires a very time-consuming hemispherical space integral operation.This paper discusses the current environmental illumination algorithms, summarizes related works, and discusses emphatically the weakness in the real-time and realistic. On the basis of the above research, we present a method for real-time rendering scenes under dynamic environment lighting. Spherical harmonics lighting is used to calculate diffuse surface illumination and screen space ambient occlusion is used to approximate global illumination effects.The main work of this paper is as follows:(1) Research dynamic environment illumination related algorithm, summarizes related works, discusses emphatically the weakness in the real-time and realistic.(2) On the basis of the above research, we present a method for real-time rendering scenes under dynamic environment lighting. The algorithm uses a spherical harmonic function to simulate the environment of light sources and the reflection process on diffuse surface. Using spherical harmonic function, the calculation process is simplified from the integral to product and plus. After simplification, the algorithm can render diffuse surface under ambient lighting in real-time.(3) After the illumination calculation, we use screen space ambient occlusion algorithm to compute object occlusion in real-time. The rendering results have more realistic because of the soft shadow generated by the occlusion.(4) The validity of the algorithm was confirmed by experiment. In this paper, we use the video screenshot to simulate the dynamic environment illumination. The results show that, the algorithm can achieve good effect under a dynamic environment light, and can render a complex model in real-time. So the rendering algorithm proposed in this paper has a certain application value in virtual reality.