[JAVA3D] Transparency problems

[James Harrison]

I am having a problem with transparency and object the intersect. 
http://www.cs.cmu.edu/~jaharris/j3d/transparency.html has some images.

If I make 3 spheres and line them up so each intersect the previous one.  Then change 
the transparency of the front most sphere(blue)assuming there are on the z axis.  I 
can just see the other 2 spheres fine.  Now if I change the 2nd sphere's(red) 
transparency from 0 to .01, then the part of the sphere that was covered by sphere 1 
has disappeared.  But, if I rotate it, then the 2nd sphere is rendered like I exepect. 
  I also use an OrderedGroup to assure that the spheres are drawn in the correct 
order.  If I do not, the transparency problem is ok, but the z buffer is incorrect.  I 
also tried using u.getViewer().getView().setDepthBufferFreezeTransparent(false), but 
this did not accomplish what I wanted.

I use NT 4 with FireGL pro 1000 8Mb, jdk1.2.2

I am doing something wrong or is this a bug?

Code:



public class Test extends Applet {
     .
 .
  .



   public TransformGroup createSceneGraph() {
 // Create the root of the branch graph
 TransformGroup objRoot = new TransformGroup();
 objRoot.setCapability(TransformGroup.ALLOW_TRANSFORM_READ);
 objRoot.setCapability(TransformGroup.ALLOW_TRANSFORM_WRITE);

 OrderedGroup objOG = new OrderedGroup();
 Sphere s1 = new Sphere(.5f);
 s1.setAppearance(S1Appear);

 Sphere s2 = new Sphere(.5f);
 s2.setAppearance(s2Appear);

 Sphere s3 = new Sphere(.5f);
 s3.setAppearance(s3Appear);

 objOG.addChild(s1);
 Transform3D t3d = new Transform3D();
 t3d.set(new Vector3f(0f,0f,.1f));
 TransformGroup tg = new TransformGroup(t3d);
 tg.addChild(s2);
 objOG.addChild(tg);

 t3d = new Transform3D();
 t3d.set(new Vector3f(0f,0f,.2f));
 TransformGroup tg2 = new TransformGroup(t3d);
 tg2.addChild(s3);
 objOG.addChild(tg2);

 objRoot.addChild(objOG);

 return objRoot;
    }

    public Test() {

 Material greenm = new Material();
 greenm.setDiffuseColor(GREEN);

 Material redm = new Material();
 redm.setDiffuseColor(RED);

 Material bluem = new Material();
 bluem.setDiffuseColor(BLUE);

 s1Appear = new Appearance();
 s1Appear.setMaterial(greenm);
 S1Appear.setCapability(Appearance.ALLOW_TRANSPARENCY_ATTRIBUTES_READ);
 TransparencyAttributes ta = new 
TransparencyAttributes(TransparencyAttributes.NICEST,0f);
 ta.setCapability(TransparencyAttributes.ALLOW_VALUE_WRITE);
 s1Appear.setTransparencyAttributes(ta);

 s2Appear = new Appearance();
 s2Appear.setMaterial(red);
 ta = new TransparencyAttributes(TransparencyAttributes.NICEST,0f);
 ta.setCapability(TransparencyAttributes.ALLOW_VALUE_WRITE);
 s2Appear.setTransparencyAttributes(ta);
 s2Appear.setCapability(Appearance.ALLOW_TRANSPARENCY_ATTRIBUTES_READ);


 s3Appear = new Appearance();
 s3Appear.setMaterial(bluem);
 s3Appear.setCapability(Appearance.ALLOW_TRANSPARENCY_ATTRIBUTES_READ);
 ta = new TransparencyAttributes(TransparencyAttributes.NICEST,0f);
 ta.setCapability(TransparencyAttributes.ALLOW_VALUE_WRITE);
 s3Appear.setTransparencyAttributes(ta);




 setLayout(new BorderLayout());
        GraphicsConfiguration config =
           SimpleUniverse.getPreferredConfiguration();

 Canvas3D c = new Canvas3D(config);
 add("Center", c);

 // Create a simple scene and attach it to the virtual universe
 TransformGroup tg = createSceneGraph();
 BranchGroup scene = new BranchGroup();
 scene.addChild(tg);
 SimpleUniverse u = new SimpleUniverse(c);

      u.getViewingPlatform().setNominalViewingTransform();
 .
  .
 .
 .
 .
 .
 BoundingSphere lightBounds =
 new BoundingSphere(new Point3d(), Double.MAX_VALUE);
        ambLight = new AmbientLight(true, new Color3f(1.0f, 1.0f, 1.0f));
        ambLight.setInfluencingBounds(lightBounds);
        ambLight.setCapability(Light.ALLOW_STATE_WRITE);
        scene.addChild(ambLight);
        headLight = new DirectionalLight();
        headLight.setCapability(Light.ALLOW_STATE_WRITE);
        headLight.setInfluencingBounds(lightBounds);
        scene.addChild(headLight);
 u.addBranchGraph(scene);
    }

    //
    // The following allows HelloUniverse to be run as an application
    // as well as an applet
    //
    public static void main(String[] args) {
 new MainFrame(new Test(), 256, 256);
    }
}

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