Thanks for your comments. What you mention is indeed a problem, and that is the non-uniform scattering of light in a droplet of water. Well, it turns out that this problem can indeed be turned to an advantage. You can use this to produce walls that are only visible from one direction but not the other, and this is indeed a good way for producing "opaque" objects, not "translucent" objects as you see in our demo. If you are interested, I'd be glad to have a discussion with you about these matters, firstname.lastname@example.org.