Are you using actually using the geometric center for the base point of these objects? Seems like each shape will have a base point definition in three.js that may or may not be the actual geometric center of the shape. Can you confirm if that is true or not? If it isn't, then using the keyword "center" here may mislead the user.

Also, when a user attaches this to a VizFrame and they also provide a vector to a point, what does the point line up with? Are these center values added to the point vector in the local reference frame of the VizFrame?