It’s been on my list for a long time but I’ve finally gotten around to writing a processor for loading and generating both flat and ellipsoidal meshes from GeoJSON. The project supports extruding shapes and generating smooth normals for projected shapes. An Ellipsoid instance from the 3d-tiles-renderer project can be provided to the loader to project objects into the same reference frame for interoperability.
You can check out the project and associated demos at @gkjohnson/three-geojson - though note that this project is not published on npm so it will need to be installed from GitHub directly.
Constrained Delaunay triangulation is used to generate shapes with internal points to ensure the entire shape can conform to the contour of the globe. This is generally slower than earcut but results a more complete triangulation with the capability for including internal vertices. There are still polygons that can fail to triangulate but hopefully those can be tracked down at some point.
