Hi,
It will be the same message from Youtube :D
I think I can give it a try.
To be honest, my shader development process is often more experimental than scientific. As I mention in the guide, a lot of features come from testing ideas and seeing what works rather than starting from a perfect technical solution. So I can't promise I'll find a good approach, but it's definitely an interesting challenge and I agree that the effect could add a lot to the overall look.
My first thought is that it might be possible to approximate it at the material level rather than through the lighting system itself. For example, by detecting the shadow transition region and applying a color shift there. That would probably require some material and texture-specific tuning, though, and it may not behave exactly like a physically-based colored penumbra.
Still, you've got me curious now. If I find a practical solution, I'll let you know!
