materials are black when loaded from PAK file

I’ve managed to set up a relatively basic custom map system using Steam Workshop and pak files. I have a template project with a custom plugin capable of cooking, packaging, and uploading the pak to steam, and then my game basically just trolls steamapps/common/workshop/content/<appid> for all pak files and mounts them at Game/Content/CustomMaps/UGC<mapid> using FPakPlatformFile.

This is (mostly) working. I am able to load the map up in my game and all the geometry is there. The issue is that this scene:


ends up looking like this when actually loaded into the game:


I know that the ‘grass’ material is found by the engine because it no longer defaults to the grey grid texture. The lens flare (?) only appeared after I turned on the forward renderer in my template project (my game uses the forward renderer). Neither the lens flare or the black material are present in the template project. I have both a skylight and a lightmass importance volume in this map.

Any ideas what I’m doing wrong? My best guess is that this is related to the pak file, but I am not sure.


So, noticing that the blue material seemed to be working okay, albeit weirdly lit, I decided to try just using that material on the landscape instead of the green one. The results were far weirder than anticipated:

[video]First Mod Map - Broken Materials - YouTube

What the hell is happening?