A longer-form personal project which came from a desire to see what soft diamonds would look like. A project which had numerous creative challenges, not the least of which was maintaining the look of the diamonds as best as possible while they were deforming from the shape that we would image them to be.
Much of our perceived look of Diamonds comes from the environment that they are in, with jewellers typically containing many small lights scattered around their premises to create many chances for jewels to sparkle. With that in mind I took the unusual step of creating my own quick HDRI enviornment to stand in for a jewellers, as my scene lights in a black void where not giving me the results I wanted.
Additionally, I had to crank up the refraction bounces beyond the default to get some nicer interior shapes in the diamonds themselves. The caustics were another challenge however after some RND and additional help from the Redshift SubReddit, I was able to achieve something I was happy with for the most part.
The rule of thumb appears to be to use a small area light or spot light as close as possible to the caustic emitting object with about 10 million caustic photons and a low search radius to get really crisp caustic shapes. Then if you output a CausticsRAW aov and a Diffuse Filter AOV then you can grade and boost the Caustics before you multply them with the diffuse in comp.