How to group intersection points from a clipping terrain

I made clipping of a terrain object using this method. I have created the intersection points as buffergeometry and rendered it as points and linesegment to visualise the result. Now I want to group these points into separate arrays (based on the circular connection) because I have to make it into other geometry of each and then turn it into a mesh and export it as a 3d object.

Anyone has an idea to do it with r.146 (as the buffergeometry has no faceindex and checked properties)?