Problem with adjusting both transparency and color of an object

Question

I am writing a program where when an object is picked, both it's transparency and color will be altered (the object will become opaque, and its color will turn to a predefined "selected" color), while the previously selected object will return to its original transparency and color. I am able to get this to work, except that objects that were picked two or more picks ago will remain in the selected color, albeit in their original transparency. This problem only seems to occur when transparency is factored in. The picking/color & transparency altering code is as follows.
public class PickingListener extends MouseAdapter {
     private PickCanvas pickCanvas;
     private TextDisplay overlay;
     private Primitive p;
     private Primitive lastP;
     private ColoringAttributes origColor;
     private TransparencyAttributes origTransparency;
     public PickingListener(PickCanvas pickCanvasArg, TextDisplay overlayArg) {
          pickCanvas = pickCanvasArg;
          overlay = overlayArg;
     public void mouseClicked(MouseEvent e) {
          pickCanvas.setShapeLocation(e);
          PickResult result = pickCanvas.pickClosest();
          if (result == null) {
               System.out.println("Nothing picked");
          } else {
               p = (Primitive) result.getNode(PickResult.PRIMITIVE);
               if (p != null) {
                    setSelectedColor();
                    overlay.setPickedBarInfo((BarInformation) p.getUserData());
               else
                    System.out.println("null");
     private void setSelectedColor() {
          ColoringAttributes barCA = new ColoringAttributes();
          TransparencyAttributes barTransp = new TransparencyAttributes(TransparencyAttributes.NICEST, 0.0f);
          barCA.setColor(ColorConstants.SELECTED);
          if (lastP != null) {
               lastP.getAppearance().setColoringAttributes(origColor);
               lastP.getAppearance().setTransparencyAttributes(origTransparency);
          origColor = p.getAppearance().getColoringAttributes();
          origTransparency = p.getAppearance().getTransparencyAttributes();
          p.getAppearance().setColoringAttributes(barCA);
          p.getAppearance().setTransparencyAttributes(barTransp);
          lastP = p;
}Capabilities to alter the primitive's color and transparency are all set.
     barAppearance.setCapability(Appearance.ALLOW_COLORING_ATTRIBUTES_READ);
          barAppearance.setCapability(Appearance.ALLOW_COLORING_ATTRIBUTES_WRITE);
          barAppearance.setCapability(Appearance.ALLOW_TRANSPARENCY_ATTRIBUTES_WRITE);          barAppearance.setCapability(Appearance.ALLOW_TRANSPARENCY_ATTRIBUTES_READ);
ColoringAttributes barCA = new ColoringAttributes();
barCA.setCapability(ColoringAttributes.ALLOW_COLOR_WRITE);
barCA.setCapability(ColoringAttributes.ALLOW_COLOR_READ);)
Any insight as to why this would occur would be greatly appreciated.
-Adrian Benton

Answer 1

A Behavior is the preferred way to make changes in a scenegraph. Here is an example from a previous post that changes the appearance of a shape when it collides with another shape.
The javadoc for javax.media.j3d.Behavior appears to refer to the issue you have.
Transparencies are confusing, different display adapters deal with them differently. Suggest you search the forum at
http://forums.java.net/jive/forum.jspa?forumID=70
for more detailed information.
regards
class CollisionDetector extends Behavior {
  private static final Color3f highlightColor = new Color3f(0.0f, 1.0f, 0.0f);
  private static final ColoringAttributes highlight = new ColoringAttributes(
      highlightColor, ColoringAttributes.SHADE_GOURAUD);
  private boolean inCollision = false;
  private Shape3D shape;
  private ColoringAttributes shapeColoring;
  private Appearance shapeAppearance;
  private WakeupOnCollisionEntry wEnter;
  private WakeupOnCollisionExit wExit;
  public CollisionDetector(Shape3D s) {
    shape = s;
    shapeAppearance = shape.getAppearance();
    shapeColoring = shapeAppearance.getColoringAttributes();
    inCollision = false;
  public void initialize() {
    wEnter = new WakeupOnCollisionEntry(shape);
    wExit = new WakeupOnCollisionExit(shape);
    wakeupOn(wEnter);
  public void processStimulus(Enumeration criteria) {
    inCollision = !inCollision;
    if (inCollision) {
      shapeAppearance.setColoringAttributes(highlight);
      wakeupOn(wExit);
    } else {
      shapeAppearance.setColoringAttributes(shapeColoring);
      wakeupOn(wEnter);
}