code: function ( geometry ) {
  
  		geometry.computeBoundingBox();
  
  		var bb = geometry.boundingBox;
  
  		var offset = new THREE.Vector3();
  
  		offset.addVectors( bb.min, bb.max );
  		offset.multiplyScalar( -0.5 );
  
  		geometry.applyMatrix( new THREE.Matrix4().makeTranslation( offset.x, offset.y, offset.z ) );
  		geometry.computeBoundingBox();
  
  		return offset;
  
  	}
docs: Center geometry so that 0,0,0 is in center of bounding box