Building lightmap for foliage breaks unless often restarted

I spent a whole day trying to figure out why my foliage weren’t making any lightmaps, everything else in the scene had a lightmap but when I switched to ‘lightmap density mode’ I could see that the foliage didn’t have any lightmap at all (that strange beige color). The message logs gave me no errors (just a warning about the LOD’s which should be irrelevant).

Eventually I figured out that the solution was to restart the engine. That fixed it!

Nowadays I’m finding myself having to restart the engine around every 3rd-5th lightmap build. Sometimes this is no big deal, other times this is super annoying when I’ve had it render all night long for a deadline only to discover in the morning that I had forgotten to restart the engine before building my lightmap.

It’s not caused by lightmass being out of memory, as my ‘windows task manager’ shows I’m never even using half of my RAM.

Hey .com,

I attempted to do a light test on my end given the context of your post. I did not see my lightmaps being discarded or any issues with my foliage rendering without a lightmap.

Are you able to reproduce this issue in a blank project using minimal assets?

If you could provide me with some simple steps to reproduce the issue on my end, we can determine if this is a bug and move forward with the troubleshooting process.

Thank you,

Hmm might be hard to reproduce since it starts happening a while into each project, but I will see if I can try later.