Michal Iwanicki

Exactly. Imagine light passing through imaginary non inf hemisphere. It's size doesn't change radiant flux.

(Imaginary non inf hemisphere inside the inf hemisphere). Radiant Flux - total emission from light source.

Outgoing flux thru sphere around a pointlight is constant bc irradiance ~ 1/r², but area ~ r²; cancels.

But a sky dome is not a pointlight, doesn't have a 1/r² falloff. Constant *irradiance* no matter size.

there is no such thing as “falloff”!only visible solid angle. For receiver sky, emissive, lights=same

Yes there is falloff. For a area light, solid angle falls off with distance. For sky dome, it does not.

sure,solid angle changes for small emissive surfaces(lights!);but concept of falloff is wrong for area L

sooner you kill concept of falloff and quadratic approx in engine/mental model,the less problems you have:)