> If you have a 1/r^2 decreasement from a point source, the if you have an infinite wall it becomes a constant value that does not decrease with the distance.
It will still decrease with distance. If you represent the wall as a collection of point sources distributed over a plane, as the distance to the plane diminishes, the distance to individual points do not diminish to and from the same distance as each other, and do not diminish at the same rate. However they still all diminish, and thus the sum intensity must diminish. Though the appropriate function describing the sum of the contributions from each point is no longer 1/d^2.
There will be some continuous equation to describe this... someone more familiar with radiance feel free to chime in!
It will still decrease with distance. If you represent the wall as a collection of point sources distributed over a plane, as the distance to the plane diminishes, the distance to individual points do not diminish to and from the same distance as each other, and do not diminish at the same rate. However they still all diminish, and thus the sum intensity must diminish. Though the appropriate function describing the sum of the contributions from each point is no longer 1/d^2.
There will be some continuous equation to describe this... someone more familiar with radiance feel free to chime in!