基于圆盘近似的动态场景柔和阴影实时绘制

Real-Time Soft Shadow Rendering of Dynamic Scenes Using Circle Splats Approximation

采用圆盘对物体表面进行近似,对每个圆盘形成的遮挡使用椭圆遮挡域表示,预计算过程中根据每个椭圆遮挡域参数进行采样并用球面调和系数表示,同时将其转换为对数,对采样数据采用主元分析方法进行压缩;在绘制的过程中,根据圆盘的法线、半径以及和阴影接收点之间的相对位置确定其椭圆遮挡域的值,然后采用球面调和指数算法进行累积.该方法将圆盘近似算法和球面调和指数算法相结合,能够灵活地描述柔性物体以及较薄的物体形成的柔和阴影.

We present a real-time rendering method for soft shadows in dynamic scenes by approximating the model surface using circle splats. The occlusion of each of the splats can be approximated using an elliptical occlusion field which is sampled in the pre-computation process. In each sample point, an occlusion cube-map of single ellipse represented by spherical harmonic coefficients is got and we transferred them to logarithm using spherical harmonic logarithm algorithm. During the rendering, we first got the log SH coefficients of each circle splat according to the its normal, radius and the distance between the splat and the receiving point, which is precomputed. We accumulate the total occlusion coefficients in log space and compute the final SH coefficients using spherical harmonic exponentiation algorithm. The algorithm combines the circle splats approximating method and spherical harmonic exponentiation algorithm. It is so flexible that it can easily render soft shadow generated by both soft objects and dynamic solid objects.