Research On Shadow Generation In Virtual Reality

Virtual Reality is already applied in many fields such as Virtual Military Training, 3D game, System Prototype Design, Virtual Manufacture, Virtual Surgery, City Planning and Virtual Distance Education. Shadow is a very important part in Virtual Reality, and it can show the relative position of the objects more clearly, so it can improve the stereoscopic impression and the lays of the graphics, and the reality of the virtual environment.Shadow rending in outdoor scene and the real-time soft shadows algorithm for dynamic scene are both the representative questions in the shadow rending field. The size of outdoor scene is larger and the objects to be rendered are so many. It is too difficult to take consideration to the quality of the shadow and the rendering speed. In real-time soft shadows rending for dynamic scene, getting the accurate width of the penumbra is a time-consuming work. It decreases the efficiency of the soft shadow algorithm. Aiming at these problems, the main works in this paper are:1. Present a split method for the outdoor scene shadow rendering.Aiming at the problems of shadow rendering in outdoor scene, basing on the view frustum split theory, we present two split formulas for shadow rendering of outdoor scene in different size. It gets the dimension of the PCF kernel for every split part according to the distance between every split part and the view point. Also, it adjusts the position of the level based on the size of the kernel. It improves the quality of shadow by PCF method.2. Present a bounding boxes assisted soft shadow algorithm for dynamic scene.Based on the analysis of the main factors which impact the efficiency of dynamic scene soft shadow algorithms, using the characteristics that the bounding box could instead of the object with the least vertices, this method quickly calculates the distance relationship among the object, light source and the receive surface, and determines the width and the location of the penumbra. Also, it could reduce the time consuming.Experiment results showed that the split method could provide good shadow effect for outdoor scene, and didn't decrease the rendering speed much more. The soft shadow algorithm assisted by bounding boxes for dynamic scene could meet the need of soft shadow real-time rending, and didn't bring serious distortion.