Oh crap, i messed up the order of the pictures. Now it's correct, I'm sorry!
The puppets are black in iray rendering because I applied a selfwritten procedural woodshader on it which can't be handled by iray. But that doesn't matter.
Because of the black bottom in the normal rendering, as far as I got it, the water creates a shadow which can only be lit by caustics. Increasing the caustics radius should fix it.
That's my mia_material:
I do not have to change anything of the iray rendering.
shader "mia_x_instance" "mia_material_x" (
shadow = "mia_x_instance"
photon = "mia_x_instance"
My job is to find a way to let the normal rendering look like the iray rendering.