Aside from buying my book that offers several tricks in this matter, you need uplighting created by a sun object, shadows off, Sun position Manual and set to altitude -90.
Like light from China,or whatever is on the other side of the world from you.
When a light doesn't cast shadows, its energy flows thru surfaces. This solves the problem that when a surface receives no lght at all, it gets really dark.
Dwight Atkinson
