. You'll be thrilled to learn the irradiance problem comes from the FUCKING COMPUTE SHADER COMPILER!!
 => I have to rewrite my time-sliced rendering using only pixel shaders I think... UU'
 => For some reason, the compute shader returns completely wrong values for the angles (based on texel index, based on threadGroupID and stuff)
 => It's not doing this on the irradiance alone but also somewhere else in the multiple scattering computation
 => The net effect is too bright values even when he Sun is below the horizon so we get a clear night with non zero values!
 => It gave me an idea though: store an ambient luminance at night in the irradiance / scattering tables! ^^

. Despite these bad news, the FUCKING HORIZON BUG is GOOOOOOOOONE!
. I also completely mastered that damn code!