How do you make caustics with yafray?

I’ve been trying to make the correct caustics for a cube using yafray but I
haven’t been able to follow their tutorial at their web site. Is there an easier way to do this? I the end I want to make a magnifying lens and fry some thing with caustics, but I haven’t been able to do it with anything so I’m going to start with a cube.

I’d like to make a cube like this only with caustics;
Help, comments, and crits about my stupidity are greatly appreciated.


It’s been a while since you posted your question. (I should pop in to this forum more often…). I think this link would help: