【作者】 唐兵；

【导师】 苗兰芳；

【作者基本信息】 浙江师范大学 ， 软件与理论， 2010， 硕士

【摘要】 在金融危机的背景下,很多产业出现了大滑坡。而游戏产业仍然保持着连续快速的增长,发展游戏产业对抵御金融危机具有一定的积极作用。目前国内的2D游戏技术已经比较成熟,而3D游戏正在蓬勃发展。在大型的3D网络游戏中,室外场景的渲染占据重要的地位。本文结合GPU的特点,从室外场景地形渲染、室外场景物体管理和室外场景的光影仿真这三个方面来研究室外场景的渲染技术。1.室外大地形渲染本文在几何裁剪图(Geometry Clipmaps)算法的基础上,结合现代游戏的特点,提出了更适合游戏室外地形的Geometry Clipmaps算法。该算法通过改善Geometry Clipmaps网格和索引组织结构,实现了一次绘制调用渲染整个地形,减少了渲染批次,充分利用了GPU批量渲染能力；并通过在相邻的粗糙层次中增加顶点索引解决裂缝和跳跃问题。采用alpha混合纹理控制地面贴图的位置和权重,使得纹理控制更加灵活。2.室外大场景物体管理利用场景图算法对场景物体进行管理,并使用四叉树算法对场景进行空间剖分,同时结合轴对称包围盒(AABB),实现场景物体快速裁剪和碰撞检测。在渲染时,对可见物体以渲染状态和材质属性进行分组,从而减少GPU的渲染状态切换,增加渲染速度。对于一些数量极多,但属性类似的物体,采用instancing实例化技术,大大的减少了渲染批次,实现一次GPU绘制调用,渲染一大批物体。3.室外场景光影仿真对于场景仿真方面,本文主要研究了光影方面的仿真。在充分比较阴影体和Shadow Maps阴影的基础上,采用了Shadow Maps阴影作为基础阴影算法,通过改善Shadow Maps算法,使用CSM (Cascaded Shadow Maps)和VSM (Variance Shadow Maps)结合,完美的解决了大规模场景动态阴影走样的问题。利用Bloom技术模拟HDR效果,加强场景的柔和和高亮效果。通过光影方面的仿真,场景真实感有了较大的提高。更多还原

【Abstract】 In the context of the financial crisis, many industries are in recession。The game industry is still maintained rapid growth, so the development of the game industry has some positive effects to resist the financial crisis. Currently the 2D games are already quite mature, however the 3D gaming is booming development. In the massively multiplayer online 3D game, the rendering for outdoor scene is very important. In this paper, combined the characteristics of GPU, the main study was focused on the terrain rendering of outdoor scenes, the management of the outdoor scene objects and the simulation of light and shadow。1. Rendering for terrainIn this paper, a more suitable algorithm for 3D game terrain real-time rendering is put forward based on Geometry Clipmaps algorithm and combined with 3D games. In this algorithm, the entire terrain can be rendered through only one Draw Call by improving the structure of grid and the organizational structure of the index, which can take full advantage of GPU. And by increasing the index of vertices in the rougher adjacent level, the issue of crack and jumping can be resolved. Using alpha blend texture to control the location and weight of the texture of terrain, it makes the control of color texture more flexible.2. Management of the outdoor scenes’objectsThe scene graph algorithms are used to manage the scene object. Combined with Axis Aligned Bounding Box (AABB), the quad-tree algorithm is used to subdivide the space of the scene, which can faster cull non-visible objects and speed collision detection. When rendering for the visible objects, the objects are sorted and grouped by their render state and material properties, in order to reduce the switch of rendering state and increase the rendering speed. For those objects with many quantity and similar properties, such as grass, instancing technology is used to render these objects. Instancing technology can render these objects only with one Draw Call, and save the graphics memory and the system memory. 3. The simulation of the light and shadowFor the simulation of scene, this paper’s study is focused on the shadows and bloom effects. Compared with the shadow volumes, shadow maps have been adopted as a basis for shadow rendering. By improving the Shadow Maps algorithm, a perfect combination of CSM and the VSM is to solve large-scale scene dynamic shadows aliasing problem。The technique of blooming used to simulate HDR effects to make the scene brighter.更多还原