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3D graphics programming in Java: Part 2, Advanced Java 3D

Learn more about Java 3D performance, 3D content loaders, and the Java 3D VRML97 browser

By Bill Day, JavaWorld.com, 01/01/99

Page 2 of 6

Behaviors can be keyed to any number of Java events or user interactions. When a user hovers near a certain object, for instance, you can cause the object to move, change color, or otherwise exhibit behavior. (In this case, the stimuli would be the user's presence inside of a specified bounds, or region, of space.)

Many behaviors can be controlled using interpolators, objects that accept a range of values to provide a time-varying behavior. You can build your own interpolators if you like, but Java 3D's built-in interpolators and Sun's utilities should suffice for most of your needs. In this month's Example 4, we modify last month's Example 3 to make the word JavaWorld rotate.

001   /**

002    * constructContentBranch() is where we specify the 3D graphics

003    * content to be rendered.  We return the content branch group

004    * for use with our SimpleUniverse.  We have added a RotationInterpolator

005    * to Example03 so that in this case, our "JavaWorld" text rotates

006    * about the origin.  We have also removed the scaling and static

007    * rotation from the text, and the scaling from our ColorCube.

008   **/

009   private BranchGroup constructContentBranch() {

010     Font myFont = new Font("TimesRoman",Font.PLAIN,10);

011     Font3D myFont3D = new Font3D(myFont,new FontExtrusion());

012     Text3D myText3D = new Text3D(myFont3D, "JavaWorld");

013     Shape3D myShape3D = new Shape3D(myText3D, new Appearance());   

014     Shape3D myCube = new ColorCube();

015 

016     BranchGroup contentBranchGroup = new BranchGroup();

017     Transform3D myTransform3D = new Transform3D();

018     TransformGroup contentTransformGroup = new TransformGroup(myTransform3D);

019     contentTransformGroup.addChild(myShape3D);

020 

021     Alpha myAlpha = new Alpha();

022     myAlpha.setIncreasingAlphaDuration(10000);

023     myAlpha.setLoopCount(-1);

024     RotationInterpolator myRotater = 

025                       new RotationInterpolator(myAlpha,contentTransformGroup);

026     myRotater.setAxisOfRotation(myTransform3D);

027     myRotater.setMinimumAngle(0.0f);

028     myRotater.setMaximumAngle((float)(Math.PI*2.0));

029     BoundingSphere myBounds = new BoundingSphere();

030     myRotater.setSchedulingBounds(myBounds);

031     contentTransformGroup.setCapability(TransformGroup.ALLOW_TRANSFORM_WRITE);

032     contentTransformGroup.addChild(myRotater);

033 

034     contentBranchGroup.addChild(contentTransformGroup);

035 

036     myTransform3D.setTranslation(new Vector3f(-0.5f,-0.5f,-2.3f));

037     TransformGroup cubeTransformGroup = new TransformGroup(myTransform3D);

038     cubeTransformGroup.addChild(myCube);

039     contentBranchGroup.addChild(cubeTransformGroup);

040 

041     return(contentBranchGroup);

042   }

By default, behaviors have no scheduling bounds and are never scheduled. You must set scheduling bounds yourself to execute behaviors in Java 3D. It's also important to remember that even with nondefault bounds specified, your behaviors may not be executed if the view platform isn't within the bounded region. This is, of course, by design, but it can make for frustrating debugging experiences if you're not careful.