Periodic Boundary Condition for Radiance geometry

I have a complex 3d model of a tree, I need to find the incident radiation on the ground below the tree. What makes it computationally expensive for me is the incident radiation below it will also depend on the surrounding tree. The trees are arranged in a grid-like pattern.
I wanted to ask if there are any methods to create a periodic boundary condition along a given direction so that I’ll have to model only one tree to get the effect of the surrounding trees as well.

You could use the “instance” primitive to copy your tree geometry as many times as you like, randomly varying size and rotation slightly if you want to get something more realistic. The replmarks program comes in handy for placing instance primatives, or you can use cnt to drive rcalc.

There’s no way to set up boundary conditions that transmit a ray from one edge back to the other as you require. It’s an interesting idea, but wouldn’t buy you any computational savings over using a lot of instances in the end.