Caustics?

I hope this is what you're looking for

AND HERE ---> As you can see the problem is the blocking liquid object. The caustics appear wherever they are not blocked. I stand corrected. Stupid me @-)

Of course caustics work with nested transparent objects. You only need to make them transparent.

For the normal transparent objects, you can say: The higher the caustics value, the sharper it's effect.

I assume, that caustics are internally implemented with a mechanism similar to phong, and then applied to the shadow, but that's just a wild guess.

The pov-source is here.

caustics=1.0 + red object

caustics=1.0 + bumps 2.5
Figure 1 Figure 2

caustics=1.0

caustics=0.5
Figure 3 Figure 4

caustics=0.25

caustics=0.01
Figure 5 Figure 6

Please send suggestions, corrections,
or just some blurb to mike AT lamertz DOT net