So I think I’ve discovered a rather large bug with volumetric lightmaps in that it’s creating a lot of unnecessary samples and ignoring the height of the Lightmass importance volume:
So here’s my test scene; just a simple landscape mesh, a skylight and directional light, all set to static.
Here is the scene post light bake:
Note the lightmass importance volume and how far off samples are generated up in the Z direction. I can understand some extra samples are necessary for ‘padding’ with this system, however this seems excessive. The result of this is VASTLY increased bake times compared to Sparse Volume Lighting Samples. For example; on a larger scene my bake time went from 20 mins with Sparse Volume Lighting Samples, to 12 hours with Volumetric Lightmaps!
I’m thinking this must be a bug??
Other than this I’ve been loving the new lightmaps so far and hope to use it but this is killing my bake times and most likely eating up a lot more memory!
Link to Answerhub page: Volumetric Lightmap Samples bug (Reproduce-able) - UE4 AnswerHub