JAVA 3D: How to animate "on-the-fly"?

Question

Hy guys,
I'm new to Java 3D and I've read a whole bunch of tutorials as well as Selman's book.
However, as great as Java 3D seems, it seems like I can't get Interpolators to work the way I want them to! Here is my goal:
Create a simulation where the View is FIXED and the main ANIMATED character (comibnation of objects) MOVE AROUND the universe through the user's keyboard commands.
I've managed the above by creating all my objects, adding them to a branchgroup, adding that branchgroup to a transformgroup, adding a few interpolator animations to the transformgroup and finally adding a cutom keyboard navigator behavior to the transformgroup.
The following problem has occurred:
I can't NICELY move the transformgroup around because I use Transform3D objects to calculate the next position of the transformgroup and I then apply it to the transformgroup by calling the "setTransform" method on that group with the Transform3D object. The result is an instantaneous leap x locale units away with no animation in between the original and final position. :o( This is the only way I got this working. The Java runtime keeps yelling at me that I can't add or remove Interpolators or transformgroups from other transformgroups or branchgroups, so I can't change interpolators on-the-fly (say, when the user wants to move in a different direction)... Can it possibly be that we can only declare and use interpolators at prior to executing a universe?!
The IDEAL solution I'm looking for (!INSERT YOUR HELP HERE! ;o) ):
Replace the ugly "setTransform" call by adding a PositionInterpolator or something to the transformgroup object in order to generate a SMOOTH ANIMATION from the original position to the final position. The end result will be must nicer and more professional.

Answer 1

Ok, I've modified the simple behavior class in order to extend the PositionInterpolator class and be able to get a translation that always begins from the last target position. Eventually, I'd also like to be able to modify the AXIS so I can change direction... Anyway, right now I just want what IWON managed to do in one direction.
Here's what I got that DOESN'T WORK, can someone please help me, IWON?:
// Allows an object or group of objects to be moved around SMOOTHLY by the keyboard.
public class KeyboardControlBehavior extends PositionInterpolator {
private TransformGroup source;
public static final float distance = 0.1f;
public static final long time = 200;
// create SimpleBehavior
KeyboardControlBehavior(TransformGroup source, TransformGroup target){
super(new Alpha(1, Alpha.INCREASING_ENABLE, 0000, 0, time, 0, time, 0, 0, 0), target);
// initialize the Behavior
// set initial wakeup condition
// called when behavior beacomes live
public void initialize(){
// set initial wakeup condition
this.wakeupOn(new WakeupOnAWTEvent(KeyEvent.KEY_PRESSED));
// behave
// called by Java 3D when appropriate stimulus occures
public void processStimulus(Enumeration criteria){
// Check which direction we're going and adjust the AXIS and endPosition
// in consequence.
KeyEvent event = (KeyEvent) ((WakeupOnAWTEvent) criteria.nextElement()).getAWTEvent()[0];
int c = event.getKeyCode();
System.out.println("KEY PRESSED = "+c);
if ( c != KeyEvent.CHAR_UNDEFINED ) {
if(c == KeyEvent.VK_UP) {
System.out.println("UP");
if(c == KeyEvent.VK_DOWN) {
System.out.println("DOWN");
if(c == KeyEvent.VK_LEFT) {
System.out.println("LEFT");
if(c == KeyEvent.VK_RIGHT) {
System.out.println("RIGHT");
// Let the PositionInterpolator animate the translation.
super.processStimulus(criteria);
// Adjust the source's position to be at the end position of the
// animation (same as target).
Transform3D newPosition = new Transform3D();
Transform3D oldPosition = new Transform3D();
source.getTransform(oldPosition);
target.getTransform(newPosition);
newPosition.mul(oldPosition);
source.setTransform(newPosition);
// Reset the Alpha class since it only executes once.
super.getAlpha().setStartTime(0);
// Consume the event.
event.consume();
// do what is necessary
this.wakeupOn(new WakeupOnAWTEvent(KeyEvent.KEY_PRESSED));
} // end of class SimpleBehavior