基于膨胀腐蚀算法的软阴影生成

Rendering Soft Shadows Based-on Swell and Erode Algorithm

针对基于阴影图的半影生成算法中生成速度慢、本影区域过大的问题,提出了基于膨胀腐蚀算法的改进算法。首先利用阴影图的深度图生成一个亮度图,并计算出阴影的半影区相对于由点光源形成的硬阴影的距离,然后利用膨胀腐蚀算法根据求得的距离对亮度图进行适当的膨胀和腐蚀,最后利用经过处理的亮度图求得最终渲染结果。算法充分利用了阴影图算法不考虑场景本身结构的特点,并利用了GPU高度并行计算的优点,可以实现实时动态的高真实感的阴影渲染,并具有抗锯齿走样的特性。

The problem of the algorithm of rendering penumbra based-on the shadow map has been discussed.The limitation of current algorithm of rendering penumbra is due to low efficiency and over-estimating the umbra region.An improved algorithm based-on swell and erode processing is put forward in this paper.Firstly,a luminance map based on the depth map of shadow map is built,and then the distance between the edge of and the umbra generated by the point light is calculated. The luminance map would be eroded and swelled by the calculated distance.Finally the photo-realistic scene with penumbra is generated while the penumbra is rendered using the processed luminance map.The algorithm fully utilizes the characteristic of the shadow map's ignoring the structure of the scene,and takes advantage of the parallel calculation of the GPU.So it can render high quality soft shadow in real-time,and has the feature of anti-aliasing.