滤波核可以设置阈值，砍掉边缘的贡献

周围像素 $j$ 包括了自己，some_of_weights 在这里不会是零，因为有包括了自己。

颜色是三通道的

Problem of Gaussian filtering:

• Also blurs the boundary
• The boundary is the high frequency that we want to keep

Bilateral Filtering 双边滤波

• Observation
  • The boundary → drastically changing colors
• Idea
  • How to keep the boundary?
  • Let pixel $j$ contribute less if its color is too different to $i$
  • Simply add more control to the kernel

问题：会不会把与噪声的差异也算进去了？

Joint Bilateral Filtering / Cross Bilateral Filtering（意思一样）

• Observation
  • Gasussian filtering: 1 metric (distance)
  • Bilateral filtering: 2 metrics (position distance and color distance)
• Especially good at denoising path traced rendering results!
• Use G-buffers
  • G-buffers are noise-free as they are not generated by multi-bounces