What I want is to force the material to only ever become as dark as that max value. For example this image:
http://puu.sh/wiZ01/fa9b7fbc0d.jpg
It is pitch black on the “dark side”, but I want to make sure I can still see the colour of the spheres even when looking at the shaded side. I could use a white cubemap to light them up, but this would just make it more white, not more of whatever colour it happens to be.
If mapping one range to another in the shading does not work, then I want to be able to clamp it to a min value of x. I tried adding a cubemap, but it affected the light side as well as the dark side.