hey alan, thanks for helping me out here. appreciate it.
seperate passes is not the way to go either i guess. i need the shadow of my object refracted in my object. if i push the ambient value of my plane shader up and render in different passes, i will indeed get:
1. a white plane
2. an object with a white refracted plane
3. a seperate shadow.
only, the shadow is the shadow without refractions. and the object just refracts the white plane, not the shadow anymore. one could leave the ambient value as it is and then do the render pass thing. one is stuck with the color of the plane (not pure white) as it is refracted in the object. post compositing in photoshop (placing a white plane behind the object) will not effect the refracted plane INSIDE the object, which therefore will keep it's own (not pure) white color.
it seems like a very simple problem, but turns out to be not so much...
especially id you have played around with this prob for a while now...
i found a workaround though. it involves using a shading map shader, a lambert and a ramp texture. you can basically let the shading map take all light parts (without shadow) of the plane and make them whiter, while not altering the shadow brightness. maya does this in post. the ramp texture needs some tweeking, but it somehow works. if someone wants to know exactly how it works, let me know and i'll post it here. it is not an ideal method though, so any other suggestions are still welcome!