Volumetric lightmap grid size is too large

Hello everyone,
Has anyone ever encountered this message and if so, what did you do to correct the issue? I am working on a big world using World composition, and have landscape mixed with areas of built up architecture, with indoors and outdoors. I have lightmass importance volumes placed in a global lights level that is constantly loaded, and these volumes are constrained to player accessible areas. I don’t have any Volumetric lightmap density volumes placed yet. This is the error message the build gets and I am wondering if placing lightmap density volumes will help correct the issue, as well as reduce the horrendous lighting build times.

this is the message:
[Resave Packages] LogLightmassSolver: Warning: Volumetric lightmap grid size is too large which can cause potential crashes or long build time, clamping from (4286, 4374, 134) to (3200, 3200, 134)

Any help would be greatly appreciated, and thanks in advance to those who take the time to read and respond:)

Are you baking light for an extremely large world?

yes as there are many artificial light sources. But I’ve been doing tests with having “sun” be stationary as well as skylight, and artificial light sources as being either stationary or static. Those messages occurred when directional was set to static, I have yet to try building with the directional as stationary.

The volumetric lightmap is stated in the docs to be active via placing Lightmass Importance Volumes too, not only volumetric lightmap density volumes. Unless that’s misinformation or outdated, then I think there’s an issue in having a whole level always loaded that contains a volumetric lightmap which is supposed to cover an entire, huge world. Have you tried changing the Volumetric Lightmap settings under World Lightmass settings? Try decreasing the first setting by 50 or 100, and increasing the memory brick data to higher (to allow more memory per volumetric sample with a lower density grid). The higher the density, the more samples that’ll be placed in the grid within the same 3D grid size, and with not enough memory brick data it could increas build times while resulting in the described error. But at a somewhat lower density with higher memory available per sample, I would think it is far less likely to crash or be too large in the world level.

thanks for the answers everyone! I have multiple (10ish) lightmass importance volumes placed in the level in various sizes, to try to constrain to surfaces and areas around gameplay. They are all in the persistent lighting level.
Using world composition, do all lightmass importance volumes need to live in a persistent level or should they be separated into the sub lighting levels associated with the sub geo levels?
are Volumetric Lighting Density volumes used more for forcing a lower density in areas or for increasing density in areas?

I’d think density lighting volumes (volumetric) are for either increasing or decreasing density in areas. Changing the World Lightmass settings for volumetric lightmaps changes the main volumetric lightmap (perhaps the first lightmass importance volume, or the non-volume based grid that is a default in a scene), or it changes all of the grids in the scene. So the VLM Density volumes are probably best utilized for changing on a per-volume, per-area basis. I’ve never seen any doc guide or advice in the forums stating that importance volumes have to be placed in a persistent lighting level, otherwise it wouldn’t work well. If I were you, though, I’d make a copy of a few sub lighting levels and move the importance volumes into the respective areas they cover in the persistent level to see if it functions correctly or better than the current setup. Make a copy of the persistent level too, or copies of the importance volumes from the persistent level to move to the sub levels.