Baking realtime GI for big levels (2k+ terrain size)

Hey all,

I’ve been struggling to get decent results for weeks now. Considering giving it up completely, I’m not sure I’m doing this right.

I’m working on several levels, using multiple terrains in multiple sizes, which together in total will be around a 3k-4k sized game. Each piece of terrain is separated into its own scene, as a complete level, with everything in it logic and art-wise.

The terrains have stones, plants, buildings, there’s an interior to some of the buildings, there are underground areas where the terrain has a hole and a tunnel goes underground (tunnel is a mesh).

I’ve been trying to find the right way to bake real time GI for this.
Since baking is scene-specific, I can’t bake each scene separately, unless there’s a way to load multiple lightmaps at the same time and have each be tied to its own scene within the game - something I understand is impossible for now.

That means I have to load all of the geometry into one huge scene, and bake it all together into a single lightmap.
A bake like this takes hours when using abysmal bake settings (0.1 realtime resolution), and I’m scared of even trying it with proper settings. It would take days, if I’m optimistic.

Beyond this, the bake sometimes comes out very wrong. Tons of artifacts and errors, and nothing works properly.

It generally feels like this is not the intended use of this system. Am I not supposed to use light baking for big worlds?

Yeah… Maybe… Even good GI systems would struggle (it would just generate a ton of data) and it certainly is not Enlighten’s strength.

With that, does baking with 0.1 look absolutely horrible? It’s not that awful for big worlds. You’re not going to get detailed GI, anyway.

Precomputed GI for terrain wouldn’t give you much. It only affects bounced light, so that would be sunlight bouncing onto the sides of any buildings that were on the terrain. Do you need that?

Most AAA games didn’t even use regular lightmaps for terrain. Games that would’ve attempted it jumped straight to dynamic lighting 5+ years ago.

Unreal Engine 3 even made a special light for this case, because lightmapping a terrain is not the smartest idea - https://udn.epicgames.com/Three/DominantLights.html#Performance impact