Strength of a rubber-band pull toward the defined direction. Only used if mode includes Position.
// Create a JointDrive, configure it and assign the JointDrive to
// the zDrive element of a configurable joint.
function Start() {
var joint : ConfigurableJoint = gameObject.AddComponent(ConfigurableJoint);
joint.targetPosition = Vector3(0,0,-10);
var drive : JointDrive = JointDrive();
drive.mode = JointDriveMode.Position;
drive.positionSpring = 20;
joint.zDrive = drive;
}