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they did it not only with compute shaders, because it runs on DX10 hardware also.
My first thought would be to upload all the lightdata in one huge uniform data block(or texture if it you are using more then u can get with uniforms).
then render the hole grid at once, and use the vertex ids to index in another uniform array which gives u the offset in the light data array and the nummber of lights in the cell.
I looked at the wolfire blog post and I think this it what they did.
blurr your skybox very strong radial around the up-axis
u can probably use the term distant fog instead of haze
then just apply fog to your geometry based on the distance
lookup the color of the fog from your blurred cubemap
finished
as they also metioned, u can use the cubemap also for the ambient color in some way. So that the cubemap alone controls the enviroment lighting of your scene