Material emitting one way for interior scene? I'm doing an interior scene seen from the outside through a big wall of glass. It's just after sunset, so there is still some light from the HDRI image. I want the light to flow to the outside. 

I don't know how many solutions that I have tested with emitting materials. If I use a plane that are located close to the celing I get too much light upwards and to solve that I use another plane between the emitting material and the celing to stop the light. Both planes are invisible for the camera and casting no shadow, but still I get a dark och almost black celing. I guess it's because I stop the light from reaching the cealing. If I lower the emitting plane, I get shadows from the side of the plane. Nothing looks nice! :(

I have made some spotlights in the celing and given them some emitting light, but not to much, because if there are too much light, they look unreal. I have six spotlights and if I increase the value to light to interior, I get a lot of strange noise on the walls.

I have also used spheres and I have to use a plane above the sphere also to stop the light.

Any other solutions or tricks to light up an interior scene? Help is preciated? Most tutorials about interior lightning is about daylight.
If I got your question right you can achieve it using a Backfacing output of a Geometry node.


Set the nodes as pictured below. Use Backfacing as a factor for mixing between Emission and Transparent nodes.


To make each side emit different light values and colors set the nodes in similar way.