Multiple baked lightmaps - limitations/possibilities?

So I haven’t gotten a chance to play with the new feature allowing for multiple baked lightmaps, but I’m very curious as to how it can perform. I’m assuming you can change the active lightmap, “profile,” so to speak, at runtime, but is it possible to, “lerp” between two, effectively fade transitioning from one to the next? This could prove to be very useful for creating high quality baked lighting, while allowing for a time of day system similar to Skyrim’s, where the time of day isn’t adjusting constantly, but rather, every few minutes, the sun position moves slightly. If the new feature allowing for multiple baked lightmaps could allow for this, could you potentially bake lightmaps for an entire day night cycle, making 24 or even 48 baked lightmaps to cycle through? Obviously this would require a long build time on the development side, and would come with its share of limitations, but it could also prove to be quite useful in certain situations.

Thanks to anyone in advance who has some insight on this subject.


No, the system is not designed for that. It has to be set which lightmap set to load before the level loads and it definitely doesn’t have any way of lerping between two lightmap sets, that would take a lot of resources.

If you insist on lightmap blending you can use my solution (little bit old): "Support for multiple static lighting scenarios" Does this mean we will finally have multi-lightmaps - General Discussion - Unreal Engine Forums

I have tried using Lighting Scenarios in this way, but only for indirect lighting. (Setting very low direct light intensity & high indirect intensity in each of the lighting scenario’s stationary directional light) This way the instantaneous transition between lighting scenarios is barely noticeable when a fully dynamic directional light is used in the persistent level as the moving sun in the sky. Unfortunately the biggest drawback with this is the level unload “hitch” is very noticeable on large maps. Even simply loading all lighting scenarios on play & toggling their visibility as the time of day goes by in game produces these hitches as well.
I would recommend you give MLDB a try instead (made by Luoshuang ^^^ )
I hope Epic implements real-time blending as a side option for lighting scenarios…not ideal for all games necessarily but this topic has come up a number of times here on the forums. If Luoshuang’s GPULightmass gets integrated into source then the only downside left would be package size of the game. 20+ sets of light maps in MLDB can’t be beat for stunning low cost pseudo-realtime GI, but does eat up quite a bit of disk space. :cool: