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Does radiosity work with skylight (directional light)? From reading online it sounds like it was intended to work with point lights but I would really like to make it work with skylight if possible.

If I did misunderstand how would I make this work with skylight?

The form factor attenuates for distance, area, and orientation of the patches. It doesn't seem like that would all apply in skylight.

I have a primitive implementation of radiosity in the cpu using ray casting.

Any help is greatly appreciated.

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Radiosity should work with any kind of light source; it's just a matter of how you define the first bounce.

After the original light sources have been considered, all the surfaces that have been hit by light rays become light sources for the second pass, and so on.

While I haven't implemented radiosity myself, I don't see why skylight/directional light wouldn't work on the first pass.

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Actually skylight is one of the best applications. Point lights or spot lights are not the best fit for radiosity. Directional lights of area lights are just great for it (because they are not changing the complexity of render).

Also read something about atmospheric scattering and its approximations to have nice sky ;).

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In radiosity, you don't usually have "point lights". Its based on radiant heat transfer between polygon faces (except we're talking about the visible spectrum of radiation instead of infrared). So every light source must be an area light source in radiosity.

You can have a really small point sphere of light.

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