Cannot understand how TransformGroup above ViewPlatform is updated.

[DoubleBarrel]

Hi, I am a Java 3d beginner.

I am currently reading the book KJGP and doing fairly well following the examples, however there is one piece of code in chapter 15 I cannot understand clearly. The comments are my current understanding of the code. Please correct me:

private void initUserPosition()
 
  {
    //get viewing platform from simple universe into vp
    ViewingPlatform vp = su.getViewingPlatform();
   
    //get the transform group above the viewPlatform into steerTG
    TransformGroup steerTG = vp.getViewPlatformTransform();

    //set t3d with the same value of steerTG
    Transform3D t3d = new Transform3D();
    steerTG.getTransform(t3d);

    //manipulate t3d's values to be looking at the values specified in lookAt. And invert.
    t3d.lookAt( USERPOSN, new Point3d(0,0,0), new Vector3d(0,1,0));
    t3d.invert();

    //make the value of steerTG the same as the values in t3d.
    steerTG.setTransform(t3d);
  }  // end of initUserPosition()

Now my problem is -how does the change in steerTG is passed to the TransformGroup above the ViewPlatform; when in the above code, the TransformGroup above the ViewPlatform isn't updated with the values in steerTG through any methods?

Thankyou for your kindness and patience.

[tom]

steerTG IS the TransformGroup above the ViewPlatform. Changing its transform will update the position of the view.

[DoubleBarrel]

So, .getViewPlatformTransform(); returns the actual TransformGroup above the ViewPlatform, and not only a copy of its contents?

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[tom]

Yes

[DoubleBarrel]

Thankyou very much Tom 
I understand now .