Car body and fixture mods should in theory export to Beam.NG just like the built in bodies and fixtures. If it works in Automation, then the exporter should be able to deal with it. One exception to this is custom materials.
Custom Materials
See Export Material User Data main page
When the exporter exports a material, it checks which base material is being used and chooses from a series of built-in handlers based on that. Custom materials that are material instances of existing car/fixture materials should already export properly. Where possible, it’s best to use instances of existing materials rather than create new ones.
Textures
Pixel formats (selected in the “Compression settings” dropdown) supported by the exporter:
- RGBA8d
- DTX1/BC1
- DXT3/BC2
- DXT5/BC3
- BC4 (Alpha)
- BC5 (Normal map)
RGBA textures will be saved with DTX5/BC3 compression by the exporter.
For best results on export, make sure the “Global Force Resident Mip Levels” option is ticked on, otherwise the texture may export down-resed, depending on whether or not Unreal feels like loading the full resolution texture at that time.