I am trying to create an effect where a bumpy billboarded texture is illuminated by a emission map that is also billboarded but is logically closer to the camera in 3D space.
In this way a blue light would be represented by a blue circle drawn on the emission map with transparency representing the brightness of the light.
The light would then illuminate the bumpy texture in the back. Because the texture is bumpy (due to a bump map) the lights might cast slight shadows and unequally light the surface.
I have no clue how to go about achieving this as I am unsure of the math involved in getting a bump map to play well with an emission map. Furthermore i am having difficulty finding a good tutorial or piece of code that represents emission maps that actually cast light onto other objects as if they were comprised of point lights.
Do you have any pointers that might help me get started?