@cyberderf: Thanks. It's a pure Maxwell.

The glass light box -> see page 1, there is a short tutorial.
@MarkM: Thanks for the comment. For the floor texture I have used UV roughness 0.3. The Bump strength is 5 and for the specular I have used a map. I must say, I have done some times a fine tune of the specular map and I decided me for less strength. The workflow is weak here, a specular factor is a must for the future.
