[BEM]

Bem.. very nice image and design indeed. One question:
Is there glass in the window? I'm still struggling to get a hard
shadow cast by windowframes etc. through windows using sun and
physical sky. All caustics are activated. Any tips?

There are windows in the frames, abbe 2000, standard settings

BEM

[Micha]

Because you have that huge plane in relation to your little room. Scale the plane almost as big as the room and you will see the caustics from the glass panels will appear much more quickly. It's a current issue with the dielectrics....

Wow, this is a very useful hint. We should get a sticky post where we could collect all this secret tricks. Maybe, Tom could create one.

[Mihai]

lol, I think I've written this scale thing in 340 posts so far.....I should put it in my sig, along with: is your scene scale correct?

[BEM]

EDIT:

" How to save alpha channel?, What kind of saving format have I to use?