Both implementations are GLSL implementations of Global Line Radiosity (more or less).
Now, it doesn’t make a lot of sense to compare 2D-GI to 3D-GI. A lot of lightpaths are just not possible in 2D so some differences must be expected. Nevertheless, I think this is very interesting.
At this point I am just doing a simple visual comparison. The scene is basically an extruded floor-plan, since (obviously) any difference in the z-dimension is impossible to render in the 2D version.
2D vs. 3D
The overall light distribution seems reasonably similar.
It is quite interesting that, even though the majority of paths is not existent in 2D, the results are very close. There is an overall difference in brightness, and also the intensities seem to falloff a bit faster in 3D.
Part 1 – Algorithm Overview, Technique
Part 2 – Tests