Swarm failed to kick off

I’m trying to build lighting in my project, but Swarm keeps failing to be “kicked off”. I’ve tried the solutions in some other threads on here regarding rebuilding unrealLightmass, but it didn’t help.

What I tried specifically is I downloaded Unreal source from GitHub (v 4.11.2), built the entire engine from scratch, and opened my project in that version of the engine (which was the same exact version as the one I had been using, just not built from source) and I got the same error with Swarm when trying to build the lighting.

Any ideas on how else to fix this?

Here’s my Swarm log: http://pastebin.com/raw/QahfJK8v

I’m not sure why it’s failing to open that mtrlgz file. If I delete all the ones in that folder, and run Swarm again, it creates these 15 files once more:

… then gets the same error. I thought it might be failing to open them because my antivirus was trying to scan them or something, but even temporarily disabling my antivirus didn’t help.

So turns out this is due to upgrading a 4.10 project to 4.11.

I have an old version of this project in 4.10, and the lighting builds fine. I just tried upgrading the 4.10 version of the project to 4.11 again, and the lighting build failed on that copy of the project with no other changes.

Sounds like a bug report in the making.

I was trying to build in 4.11 in a project I had upgraded from 4.10. My log is posted in my other comment: http://pastebin.com/raw/QahfJK8v.

I’m not sure what you mean by source or release, I was building lighting only out of the editor.

what engine are you using? source or release build? could you post the log of the building process?