As I understand it, Geometry stores a javascript object structure of the vertices and faces and BufferGeometry just stores the raw gl data via Float32Arrays, etc.
Is there any way to turn standard Geometry into BufferGeometry, which is a lot more memory compact with less objects? For example if I create a new SphereGeometry, is there a way to easily transform that to a BufferGeometry?
You are in luck.
EDIT: updated to three.js r.76