This solves a limitation that EdgesGeometry has. EdgesGeometry can’t be used to find cluster of faces and the proper edges associated with them based on a threshold angle.
Source: https://github.com/bytezeroseven/THREE.RegionGeometry
Demo: https://bytezeroseven.github.io/THREE.RegionGeometry/
The geometry adds Face3.regionIndex for interactivity. The faces of a region can be accessed using RegionGeometry.regions[ Face3.regionIndex ] .
The regions and edges can be updated using RegionGeometry.update( thresholdAngle ) .
I use it for flood filling the faces in my paint app.