public void preRotate(float angle, float ax, float ay, float az) {
   Transform t = new Transform();
   t.postRotate(angle, ax, ay, az);
   t.postMultiply(orientation);
   orientation.set(t);
 }
 public void setOrientation(float angle, float ax, float ay, float az) {
   orientation.setIdentity();
   orientation.postRotate(angle, ax, ay, az);
 }
 public void postRotate(float angle, float ax, float ay, float az) {
   orientation.postRotate(angle, ax, ay, az);
 }