Cineversity

I was going over the new tutorial on SSS and I had a question.  Let’s say that I want to recreate “peas in a pod” where the pod has subsurface scattering but each pea blocks light so that you see dark areas wherever the pea is. I want the peas to be fully contained in the pod (no cheats with the peas outside creating shadows) and recreate the backlit effect as in the picture.

How do I recreate the more dense regions to give the effect?

The implementation used to calculate SSS does not support intersections. Which sucks, but is actually present in many modern SSS approximations.

So the easiest solution, as I’m sure you know, is out the window, and using a volume is out.
now you can add thickness to the walls of the pod, and this works to an extent with the GI casting rays…but if you split the 2 sides so that they are now separate entities to the SSS shader then you get better results.

Now, SSS does react to the intensity of light rays. (direct light / shadows).

If your peas were on the opposite side of the peapod then they would block the rays that would provide illumination. So it works through 1 layer of thickness.

Now when a ray exits the surface it no longer carries anything other than the color that should be delivered to a pixel…so it dies as soon as it exits…that means you lose any effect on the second level of thickness.

so you need to be able to send a second intensity value with the exiting ray…this means you need to use a GI solution to allow the intensity to travel.

All that said…this implementation of SSS is generally used for deeper scattering and more voluminous objects, so using an alternate solution would be best, although off the top of my head I’m not to sure where I would go.
Probably to the suggestion form to ask for support of intersecting objects haha.