@enkonyito
I feel a fool now, [:(|)], i thought the 20h and 21h referred to the render time, 21 hours to render an image!!! i was never gonna go near caustics.
@martin
Beautiful image yet again, i can see how an outside light source would "shine" through the large windows and onto the floor, but on the area just outside the main room the "shine" also appears square, i cannot figure that out [:(]