【作者】 秦合森；

【导师】 顾耀林；

【作者基本信息】 江南大学 ， 计算机软件与理论， 2008， 硕士

【摘要】 全局照明计算是一种重要的基于物理光学原理的计算机图像合成方法.在光滑的平面上,它也是特别重要的,因为它以光滑材料特征的正确感知为条件.这篇论文主要集中于在光滑平面上的高效全局照明计算.在这些平面上,如果只用纯粹的蒙特卡洛取样是非常困难的。因为太多的光线需要进行适当的评估计算。本文提出了一种在光滑表面上计算间接照明的光线跟踪算法。这个算法的优点是能够通过一组稀疏的被存储在高速缓存中的辐射亮度对光滑表面进行插值取得快速的全局照明计算。本文讨论了该方法的几个必要因素:(1)在表面上的辐亮度自动选择存储;(2)使用球谐函数表示的辐亮度;(3)光滑平面的平移梯度计算。相对于已经存在的光线跟踪算法,本文的方法能够在更短的时间内生成高质量的图像。它能够被用在双向全局照明和单一的全局照明算法中。更多还原

【Abstract】 Computation of global illumination is an important means in the pursuit of photorealism of computer-generated images. It is of particular importance in scenes with glossy surfaces, since it conditions correct perception of glossy material characteristics. This dissertation focuses on efficient computation of global illumination in presence of glossy surfaces. Computing global illumination on those surfaces is difficult with pure Monte Carlo sampling because of the sheer number of rays required to get a good estimate of indirect illumination. This paper proposes a ray tracing-based algorithm for computing indirect illumination on glossy surfaces .The algorithm takes advantage of the shading smoothness on these surfaces by interpolating indirect illumination from a set of sparsely distributed, cached values. We discuss all the components necessary for an implementation: (1) an automatic choice of surfaces on which radiance caching is used; (2) compact representation for the cached illumination by spherical harmonics; (3)Computation of translational gradient for smooth interpolation. Our method delivers high quality images in a shorter time compared to existing ray tracing-based methods. It can be used for final gathering in two-pass global illumination methods or as a stand alone global illumination algorithm.更多还原