are the Moving? if not do like he said render then out and perhaps project them back into the scene as a gobo on a spotlight. should be easy to do. I have faked them like that before even in offline rendering just because it was to much render-time to calculate the same thing over and over again. I mean they dont move and unless the object making them moves or the surface they are landing on moves. If both of them are static I suggest baking one out and taking it into Photoshop and making a projectable texture and bring it in that way.