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学科主题: 计算机应用
题名:
基于阴影图的阴影实时绘制算法
作者: 章曼
答辩日期: 2010-05-28
导师: 吴恩华
授予单位: 中国科学院研究生院
授予地点: 北京
学位: 硕士
关键词: 阴影图 ; 高次幂函数 ; 逼近 ; 反走样 ; 泰勒展开
摘要: 形影不离,指形体和它的影子分不开,宛若真实世界中,有光的存在必然有影的出现——光影相随才是真实场景中最常见的景象。因此,在真实感图形绘制中,要逼真地反映真实世界,绘制结果中必须包含阴影以体现真实的光照效果。随着真实感绘制要求的不断提高,快速有效的阴影绘制逐渐成为研究热点同时也是难点问题。 阴影绘制的难点体现在如何平衡精确度和速度两方面的要求:绘制较精确的阴影会牺牲速度,而速度较快的阴影绘制,其效果却平平,很难做到两者兼顾。可以说,阴影绘制算法研究的核心问题就是如何快速甚至实时地绘制出高质量的阴影。而影响阴影实时绘制效率的因素主要有两个:一是场景的复杂度,二是光源的数目。场景复杂度越高,物体之间相对位置就越复杂,遮挡关系也因此变得更复杂。而光源数目越多,使得阴影区和光照区边界的区分、以及阴影区内阴影亮度的计算,都变得更加有难度。 本文首先介绍了阴影绘制算法的发展历史,着重介绍和分析了基于阴影图的阴影实时绘制算法,随后提出一种基于高次幂函数的阴影实时绘制算法。此算法用高次幂函数来逼近传统阴影图算法中的二值深度测试函数,得到变化连续的阴影亮度值,从视觉上消除传统阴影图算法中的锯齿现象,达到反走样的目的。高次幂函数采用泰勒展开式进行展开,保留有限项进行预滤波,算法速度和精确度都得到了很好的保证。实验结果表明,该算法在现有图形硬件中能够达到很好的效果。
英文摘要: Shadow is a common phenomenon in our daily life which accompanies with the appearance of light. In order to render scenes more realistically, the rendering process must include shadow algorithm to depict the real lighting results. Among advanced realistic rendering techniques, effective and real shadow rendering recently becomes a popular but difficult research subject as well. Good performance and high quality are two essential requirements in the shadow rendering. And it is difficult to satisfy both of the two requirements because fine rendering results always demand more computing. Therefore, the key research of shadow algorithms is to render high-quality shadow as fast as possible, even in real time. However, there are mainly two factors that impact the performance of real-time shadow rendering algorithm: the complexity of scenes and the amount of light sources. The high scenes complexity leads to the complex occlusion relationship of objects. Moreover, the extraction of shadow boundaries and the calculation of shadow value will both cost more computing because of multiple light sources. This thesis first introduces the development history of the shadow algorithms and emphasizes the real-time shadow rendering algorithms using shadow map. Then it presents a real-time shadow rendering algorithm based on the high-order power function approximation of the conventional binary-value depth test function. This anti-aliasing algorithm can be used to obtain continuous shadow values and remove the aliasing which comes up in the conventional shadow map. The high-order power function is approximated by the Taylor expansion and only the first several items of the Taylor expansion is retained for pre-filtering. The new algorithm has high frame rate and well accuracy. Experimental results show that the algorithm can be used to achieve good results with the current graphics hardware.
语种: 中文
内容类型: 学位论文
URI标识: http://ir.iscas.ac.cn/handle/311060/2287
Appears in Collections:计算机科学国家重点实验室 _学位论文

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Recommended Citation:
章曼. 基于阴影图的阴影实时绘制算法[D]. 北京. 中国科学院研究生院. 2010-05-28.
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