as seen from the image using an external light source, the walls are almost transparent to light (shade of light to 1.000)

in view of the outer wall is invisible to afford to work.

There is possibility to solve the problem, otherwise it is impossible to use an external light.

thanks

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