Examples and demos for gemini-viewer sdk, which is a WebGL based BIM model viewer, built on three.js. It is used to view dwg/dxf, gltf, obj, ifc models, etc.
These are called Markup in this project, and implemented in MarkupPlugin. We are able to get them, store in you own database, etc. and set back to this platform.
Please take a look at these APIs
I want to be able to save the DXF file of the annotation after the annotation, ask the author I change how to implement