message: better box3d calculation in boundary-helper
diff: @@ -77,9 +77,12 @@ export class BoundaryHelper {
  }
  getBox(box?: Box3D) {
  - // TODO can we get a tighter box from the extrema???
  if (!box) box = Box3D()
  - return Box3D.fromSphere3D(box, this.centroidHelper.getSphere())
  + Box3D.setEmpty(box)
  + for (let i = 0; i < this.extrema.length; i++) {
  + Box3D.add(box, this.extrema[i])
  + }
  + return box
  }
  reset() {
  