Hi Han5,

Interesting that you should post this, yesterday I have been further tweaking the caustics settings, to hopefully improve things even more.

Having a quick look at your model, the top part is blue because it is the sky, your yellow wall is only 100cm high. [:)]

Will try some further tests this evening!

db4tech

Edit:

Could the colour of the blocks on the right be being ignored because it has the "g sweethome3d_window_pane" name set, so it is made invisible when rendered?