code: function BoundVector3D( px , py , pz , vx , vy , vz ) {
  	this.position = new Vector3D( px , py , pz ) ;
  	this.vector = new Vector3D( vx , vy , vz ) ;
  }
docs: "Vecteur lié" A starting point/position and a vector, i.e. vector applied on a point/position.