Part One

Start from a simple applet:

import java.applet.Applet;

public class HelloU extends Applet {

}

This compiles nicely.

We add an empty constructor, and a main method.

import java.applet.Applet;
import com.sun.j3d.utils.applet.MainFrame;

public class HelloU extends Applet {

  public HelloU() { } 

  public static void main(String[] args) {
    new MainFrame(new HelloU(), 256, 256); 
  }

}

Now you can compile and run this program, but what do we have?

import java.applet.Applet;
import com.sun.j3d.utils.applet.MainFrame;

public class HelloU extends Applet {

  public HelloU() { } 

  public static void main(String[] args) {
    new MainFrame(new HelloU(), 256, 256); 
  }

  public void init() {

  }

  public void destroy() {
    u.removeAllLocales(); 
  } 

  private SimpleUniverse u = null; 

}

The program above does not compile. Why?

import java.applet.Applet;
import com.sun.j3d.utils.applet.MainFrame;
import com.sun.j3d.utils.universe.*; 
import java.awt.BorderLayout; 
import java.awt.GraphicsConfiguration; 
import javax.media.j3d.*; 

public class HelloU extends Applet {

  public HelloU() { } 

  public static void main(String[] args) {
    new MainFrame(new HelloU(), 256, 256); 
  }

  public void init() {
    setLayout(new BorderLayout()); 
    GraphicsConfiguration config = SimpleUniverse.getPreferredConfiguration(); 
    Canvas3D c = new Canvas3D(config); // http://java.sun.com/products/java-media/3D/forDevelopers/J3D_1_3_API/j3dapi/javax/media/j3d/Canvas3D.html 
    add("Center", c); 
    u = new SimpleUniverse(c); 
  }

  public void destroy() {
    u.removeAllLocales(); 
  } 

  private SimpleUniverse u = null; 

}

Now it compiles, runs and you can even see a small change in its appearance.

import java.applet.Applet;
import com.sun.j3d.utils.applet.MainFrame;
import com.sun.j3d.utils.universe.*; 
import java.awt.BorderLayout; 
import java.awt.GraphicsConfiguration; 
import javax.media.j3d.*; 

public class HelloU extends Applet {

  public HelloU() { } 

  public static void main(String[] args) {
    new MainFrame(new HelloU(), 256, 256); 
  }

  public void init() {
    setLayout(new BorderLayout()); 
    GraphicsConfiguration config = SimpleUniverse.getPreferredConfiguration(); 
    Canvas3D c = new Canvas3D(config); 
    add("Center", c); 
    BranchGroup scene = createSceneGraph(); 
    u = new SimpleUniverse(c); 
    u.getViewingPlatform().setNominalViewingTransform(); 
    u.addBranchGraph(scene); 
  }

  public BranchGroup createSceneGraph() {
    BranchGroup objRoot = new BranchGroup(); 

    return objRoot; 
  } 

  public void destroy() {
    u.removeAllLocales(); 
  } 

  private SimpleUniverse u = null; 

}

The scene has been set for what we want to show:

import java.applet.Applet;
import com.sun.j3d.utils.applet.MainFrame;
import com.sun.j3d.utils.universe.*; 
import java.awt.BorderLayout; 
import java.awt.GraphicsConfiguration; 
import javax.media.j3d.*; 
import com.sun.j3d.utils.geometry.ColorCube; 

public class HelloU extends Applet {

  public HelloU() { } 

  public static void main(String[] args) {
    new MainFrame(new HelloU(), 256, 256); 
  }

  public void init() {
    setLayout(new BorderLayout()); 
    GraphicsConfiguration config = SimpleUniverse.getPreferredConfiguration(); 
    Canvas3D c = new Canvas3D(config); 
    add("Center", c); 
    BranchGroup scene = createSceneGraph(); 
    u = new SimpleUniverse(c); 
    u.getViewingPlatform().setNominalViewingTransform(); 
    u.addBranchGraph(scene); 
  }

  public BranchGroup createSceneGraph() {
    BranchGroup objRoot = new BranchGroup(); 
    TransformGroup objTrans = new TransformGroup(); 
    objTrans.setCapability(TransformGroup.ALLOW_TRANSFORM_WRITE); 
    objRoot.addChild(objTrans); 
    objTrans.addChild(new ColorCube(0.4)); 
    
    return objRoot; 
  } 

  public void destroy() {
    u.removeAllLocales(); 
  } 

  private SimpleUniverse u = null; 

}

Compile and run the program. What changes do you notice?

import java.applet.Applet;
import java.awt.BorderLayout; 
import java.awt.GraphicsConfiguration; 
import com.sun.j3d.utils.applet.MainFrame;
import com.sun.j3d.utils.geometry.ColorCube; 
import com.sun.j3d.utils.universe.*; 
import javax.media.j3d.*; 
import javax.vecmath.*; 

public class HelloU extends Applet {

  public HelloU() { } 

  public static void main(String[] args) {
    new MainFrame(new HelloU(), 256, 256); 
  }

  public void init() {
    setLayout(new BorderLayout()); 
    GraphicsConfiguration config = SimpleUniverse.getPreferredConfiguration(); 
    Canvas3D c = new Canvas3D(config); 
    add("Center", c); 
    BranchGroup scene = createSceneGraph(); 
    u = new SimpleUniverse(c); 
    u.getViewingPlatform().setNominalViewingTransform(); 
    u.addBranchGraph(scene); 
  }

  public BranchGroup createSceneGraph() {
    BranchGroup objRoot = new BranchGroup(); 
    TransformGroup objTrans = new TransformGroup(); 
    objTrans.setCapability(TransformGroup.ALLOW_TRANSFORM_WRITE); 
    objRoot.addChild(objTrans); 
    objTrans.addChild(new ColorCube(0.4)); 
    Transform3D yAxis = new Transform3D(); 
    Alpha rotationAlpha = new Alpha(-1, 4000); 
    RotationInterpolator rotator = new RotationInterpolator(rotationAlpha, 
                                                                 objTrans, 
                                                                    yAxis, 
                                                                     0.0f, 
                                                    (float)Math.PI * 2.0f); 
    BoundingSphere bounds = new BoundingSphere(new Point3d(0.0, 0.0, 0.0), 100.0); 
    rotator.setSchedulingBounds(bounds); 
    objRoot.addChild(rotator);     
    return objRoot; 
  } 

  public void destroy() {
    u.removeAllLocales(); 
  } 

  private SimpleUniverse u = null; 

}

Now the program is in almost its final state.

import java.applet.Applet;
import java.awt.BorderLayout; 
import java.awt.event.*; 
import java.awt.GraphicsConfiguration; 
import com.sun.j3d.utils.applet.MainFrame;
import com.sun.j3d.utils.geometry.ColorCube; 
import com.sun.j3d.utils.universe.*; 
import javax.media.j3d.*; 
import javax.vecmath.*; 

public class HelloU extends Applet {

  public HelloU() { } 

  public static void main(String[] args) {
    new MainFrame(new HelloU(), 256, 256); 
  }

  public void init() {
    setLayout(new BorderLayout()); 
    GraphicsConfiguration config = SimpleUniverse.getPreferredConfiguration(); 
    Canvas3D c = new Canvas3D(config); 
    add("Center", c); 
    BranchGroup scene = createSceneGraph(); 
    u = new SimpleUniverse(c); 
    u.getViewingPlatform().setNominalViewingTransform(); 
    u.addBranchGraph(scene); 
  }

  public BranchGroup createSceneGraph() {
    BranchGroup objRoot = new BranchGroup(); 
    TransformGroup objTrans = new TransformGroup(); 
    objTrans.setCapability(TransformGroup.ALLOW_TRANSFORM_WRITE); 
    objRoot.addChild(objTrans); 
    objTrans.addChild(new ColorCube(0.4)); 
    Transform3D yAxis = new Transform3D(); 
    Alpha rotationAlpha = new Alpha(-1, 4000); 
    RotationInterpolator rotator = new RotationInterpolator(rotationAlpha, 
                                                                 objTrans, 
                                                                    yAxis, 
                                                                     0.0f, 
                                                    (float)Math.PI * 2.0f); 
    BoundingSphere bounds = new BoundingSphere(new Point3d(0.0, 0.0, 0.0), 100.0); 
    rotator.setSchedulingBounds(bounds); 
    objRoot.addChild(rotator);     
    objRoot.compile(); 
    return objRoot; 
  } 

  public void destroy() {
    u.removeAllLocales(); 
  } 

  private SimpleUniverse u = null; 

}

What's the benefit of the last few added pieces?