I’ve used Three.js and it’s OBJ exporter in an Electron app that allows people to view and export maps from Build Engine games including: Duke Nukem 3D, Shadow Warrior and Blood.
Full source code is available: GitHub - Steveeeie/build-engine-map-exporter: A map export tool for Build Engine games, including Duke Nukem 3D, Shadow Warrior, and Blood.
Windows and Mac builds are available under releases: Releases · Steveeeie/build-engine-map-exporter · GitHub
