Effectatron shows how to render caustics using C4D and Redshift, with a few tips to speed up rendering.

Check out this tutorial from Derek Kirk (Effectatron), which shows how to create great-looking caustics in Redshift while in Cinema 4D.

The tutorial is a bonus lesson from Motion: An Interactive Workshop, going through the lighting section in Chapter 2. Mind and Motion is An Interactive Redshift, C4D, and Mental Health Workshop where you can learn C4D and Redshift with 100+ Video Lessons. Learn more about the workshop here.