Research And Implementation On Technique Of Rendering For Large-scale Outdoor Scene In 3D Game Engine

The Outdoor Scene Rendering is a very imaportant element of 3D game technology, particularly in online games. It is also the core of 3D graphics engine. The technology also can be applied to other fields, such as Virtual Reality, 3D GIS, Data Visualization. With the continuous development of hardware, we need to get more large-scale and more realistic scenes using Optimization algorithm or new algorithm.This paper analyses simplified algorithms for terrain's meshes, by comparing ROAM(Real-time Optimal Adaptive Meshes), LOD(levels of Details) algorithm base on quadtree, GeoMipMap(Geometrical Mipmapping). Then we proposes a new terrain rendering optimization algorithm base on Geometrical Mipmapping, which is well-suited for modern GPU and balance the load between CPU and GPU. This algorithm used linear interpolation to avoid image error due to grid's resolution changes. To reduce CPU's workload, lookup-table was used to generate block's grids. In addition, data of vertex cached in graphics card could avoid the large volume of data transmission between GPU and CPU. The experimental data show this algorithm can not only improve drawing efficiency largely but also generate image with higher quality. Through researching the methods of loading terrain's data, the paper presents a new dynamic loading algorithm. It can be used to render huge even unlimited scenes.The paper describes management of space and culling of grids in terrain rendering. In implementation, the paper chooses quadtree to manage the space of terrain. On the other hand, with bounding box, we cull the blocks which make up of terrain out of frustum. The realistic scene rendering technologies including multitexture blending technology which simulates the surface of earth, light textures representing light and shadow, generation of the plant meshes, simulation of fog, and sky box are introduced in paper.