Abstract: The Percentage-Closer Soft Shadows（PCSS） technique can generate perceptually accurate soft shadows.PCSS is based on the observation that as the size of the PCF kernel increases，the resulting shadows become softer.The challenge is to vary the filter size intelligently to achieve the correct degree of softness.Using Poisson disk sampling to do the blocker search and the PCF filtering，banding can be reduced without unduly increasing the number of samples.Using a variable depth bias in the direction of the local depth gradient inside the PCF kernel can handle the self-shadowing.So the improved PCSS technique can generate more perceptually accurate soft shadows.

摘要： 百分比靠近软阴影算法可以生成视觉上逼真的软阴影，它是基于PCF内核的，随着PCF内核的增大，生成的软阴影逼真度越高，该算法的关键是通过变化滤波内核的大小来获得高质量的软阴影。在算法的遮挡物查找和滤波阶段，使用泊松圆盘采样来处理由于不适当地增加采样数目而产生的带状走样。同时在PCF内核中使用深度梯度来得到可变的深度偏移值，进而处理自阴影问题，改进了百分比靠近软阴影算法，从而生成更准确，更逼真的软阴影。