The new MM3D files work with this: https://github.com/mick-p1982/mm3d/releases

More info and tools: http://www.swordofmoonlight.net/bbs2/index.php?topic=319.0

July 2023, now SOM_MAP and SOM_PRM use MM3D/mm3d-portable.exe folder to open
MM3D files with Alt+Click. The [Editor] do_not_open_with_mm3d extension will
use the Windows Explorer "Open With" association

====About MM3D====
    
Multimedia 3D
https://github.com/mick-p1982/mm3d
Copyright c 2019-2023 Mick Pearson

Maverick Model 3D
https://clover.moe/mm3d/
Copyright c 2009-2019 Zack Middleton

Misfit Model 3D
http://www.misfitcode.com/misfitmodel3d/
Copyright c 2004-2008 Kevin Worcester