Real-Time Shadow Rendering Technology In Large-Scale Virtual Environments

Shadow is an important factor in three-dimensional scene，It can not only providelocation information to geometry of objects in space, but also enhance the realism ofthe scene. Shadow maps as a algorithm with high efficiency, complexity does notdepend on the characteristics of the scene, but aliasing affect the prospects for itsapplication, and real-time dynamic shadow rendering for large-scale scene, It iscurrently facing a major dilemma to solve the problem of reality and real-·timeperformance in the shadow generation.In this paper, Taking into account both realistic and real-time, the shadow mapsalgorithm will be improved. The major research and innovation are as follows:We elaborate on the Graphics Processing Unit and shadow rendering techology.Shadow maps,Shadow Volumn,parallel split shadow maps, variance shadow maps arecompare these algorithms and the characters of them. The algorithm was implementedin VS2005and Microsoft’s DirectSDK, HLSL will as a shading language.Aiming at the problem of PSSM, Firstly,In the scene model data generationapproach based LOD techniques, and the Z value to the organization model data, thehigher part of the depth values, using the more simple model, from the point of viewthe more recent position, with full details of the model. For the view frustum theory,there is insufficient space first division after division and aliasing with all layer on theshadow boundary region.We present a new way to adjust the position of the viewfrustum. This algorithms calculate penumbra with PCSS, it is Parameter to computerScale factor with Logarithmic split,and geometric progressive based on thepenumbracomputer other split layer kernel. This approach is equivalent to increasingthe depth of texture resolution and it will increase the speed and increase the effect ofthe shadow of the scene.Aiming at the problem of aliasing with all split scene.we present combine theparallel-split shadow maps algorithm with variance shadow maps algorithm,thisapproach not only this question will be sloved to a depth map can not meet therequirements of accuracy. But also texture filtering techniques can be applied to thedepth maps.this techniques is pre-filter way, it is include mip-map,anisotropic filter,vsm etal, the new approach adding a Gaussian blur to the shadow boundary region.Blur to the shadow generated closer to making soft shadows. Finally, Using PSSM and VSM hybrid algorithm efficiency is not obvious torendering the shadow, but a significant effect of the generation of shadow.