Is it possible for me to use more than one LightMass Importance Volume, or is it a bad idea? I’m asking because I know it’s important to cover only the areas that are being used. I figured using more than one, like two or three, would be a good idea so I’ll have better control over what’s in the volume
Using more than one is absolutely fine. It’s even OK to edit the volume so that it is more tightly fitting to your playable area. The idea behind them is to have them in playable areas where having better shadow quality is important, because anything outside of the volume will only get a single bounce and lower quality shadows.
It’s also best to not scale these to be extremely large either.
I hope that helps,
Since this is the first result on Google I would like to share a more detailed information:
“If you place multiple Lightmass Importance Volumes, most of the lighting work will be done with a bounding box that contains all of them. However, Volume Lighting Samples are only placed inside the smaller volumes.”