Shadow Algorithm Of Three-dimensional Graphics Applications

Shadow in 3D graphics system has some advantages, such as reflecting relationship of occlusive objects, enhancing graphic realism and performing differences of angle. So, the shadow effect is indispensable in 3D graphic system. Today, the shadow has been widely used in 3D games, simulation systems, and virtual reality systems. A lot of algorithms about generating realistic soft shadow have been presented in recent years. Unfortunately, these algorithms have many disadvantages, such as low speed and poor realistic.This paper which is based on the programmable characteristics of modern graphic processor, does a solid research on shadow algorithm. It discusses and analyzes some popular hard shadow algorithms and soft shadow algorithms, which are used in 3D real-time systems. Though analyzing of shadow algorithm, it chooses the algorithm that is based on Gaussian blur to improve. The algorithm has some problems, such as bias problem, aliasing problem and one problem that affects none-shade part of image and is caused by Gaussian blur. To solve these problems, this paper makes some improvement on the algorithm. Firstly, it uses the Woo's average depth principle and PCF algorithm to solving bias problem and aliasing problem; secondly, it designs and implements an effective method to control the range of blur; thirdly, it adapts any size texture to story information. This method for keeping information plays important part on raising realistic graphic; fourthly, it takes use of the technology of programmable graphics hardware and the method of FBO to improve efficiency of algorithm.After the improved algorithm is carried out, the paper evaluates the improved soft shadow algorithm in three aspects, the rendering speed, the rendering effect and the adaptability to complex scene. The improved algorithm has many good characteristics such as better graphic effect, real-time and strong adaptability of complex scene. The improved soft shadow algorithm has been applied to Drilling Simulator Graphic System. It adds a real-time and dynamic soft shadow graphic effect on Drilling Simulator Graphic System. So, it enhances the graphic realism and makes a solid foundation for future development.