What kind of Directional light map algorithm does UE3 use on mobile?

I noticed that UE3 adopts a very interesting directional light map solution that is similar to Valve’s.
However there is only one irradiance value for each light map pixel, which is three in Valve’s solution.

Is there any documentation explaining the idea behind it?


Light Maps themselves are baked on PC before you even deploy to mobile, and the same light maps are used when you deploy too (so long as they’re sensible sizes, otherwise they’ll be reduced). UE4 does actually use three samples by default I believe, and you can go up to ten if I remember correctly. Not sure on that last part, been a long time since I’ve used Lightmass.

Dynamic GI isn’t a mobile feature yet, possibly with the exception of Tegra devices, but you’ll need the source code version of the engine to use that.