Hello BB, meanwhile thanks to all and especially to you for the constant explanations.

Your last picture is very similar to the effect that I want to play, the technique you used is similar to what I tried I also, of course I have not received your results, but knowingly exploit your advice.

the problem of this approach is that obviously if you've already built an environment in some cases it is difficult to play, then if you frame the roof, this does not exist.

Poser Pro 2014 SR 1 on Windows 7 64 bit
I use IDL, Gamma Correction and EZSkin for all final renders.