The Research And Application Of Real-time Shadow Rendering Technology

With the rapid development of computer graphics in recent years, higher demandsfor realistic images’ quality and quantity are proposed in many areas. However, animportant factor affecting the image realism is shadow, which shows the information oflight illuminating on an object and meanwhile is a reference in people’s cognitiveworld, playing an important role in people understanding the positional relationshipamong objects in the world. In the virtual scene, the shadow cannot be ignored.Accurate shadow effects can help us understand the spatial location of objects, thusenhance the realism in virtual scene, making the scene look more realistic. However, inthe dynamic three-dimensional scene, how to guarantee real-time performance, and inthe meanwhile render shadows with high quality and strong sense of reality is still achallenge.In the past30years, researches into real-time shadow generation algorithm hadbeen carried on and a lot of excellent shadow generation algorithm was proposed. Inthe graphics fields, shadows can be divided into hard shadows and soft shadows,respectively corresponding to hard shadow algorithm and soft shadow algorithm. Fromanother point of view, shadow algorithm can be divided into two categories: the onebased on image space and the other one based on object-space. In hard shadows, lightis assumed to come from an ideal point source and umbra is considered rather thanpenumbra. Hard shadow algorithm is very important in computer graphics and it is thebasis of soft shadow algorithm. All the soft shadow algorithms are extensions from thehard ones. Thus, the hard shadow algorithm determines the direction of the softshadow algorithms.This paper mainly introduces the shadow mapping technique, shadow volumetechnique and some classic shadow algorithm based on those techniques. Shadowmapping technique is a graphic-space-based shadow rendering technology, which firstrenders the depth information in scene taking light source as the viewpoint. The depthinformation determines the overall shadowing situation in scene. The shadow volumetechnique is a geometry-based shadow generation technology. Its main idea is to distinguish between shaded area and non-shaded area and determine pixel’s visibilityafter that. In this paper we focus on the principles and implementation of algorithms,also analyze and compare the advantages and disadvantages of them. In our project, wechoose the variance shadow maps (VSM) algorithm to implement. VSM is animage-space-based shadow mapping algorithm, whose final shadow generation resultgreatly meets our needs for dynamic real-time performance. In the end, we proposesome valuable direction for further research according to current development trends.