3.2 Your first Java 3D application | JAVA 3D Programming | Chapter 3

3.2 Your first Java 3D application

         The SimpleTest example (figure 3.1) is intended to build upon the HelloUniverse example that comes with the Java 3D distribution. I’ve attempted to expand upon HelloUniverse by documenting the relationships between the various constructs used in the example and showcasing some of the features of Java 3D that enable you to build fairly complex applications with very little code. This example is 280 lines (less than 100 without comments) and illustrates some fairly complex functionality:

Figure 3.1 The SimpleTest example. One hundred lines of Java code give you an animated scene, including a graphical textured background with directional lighting

Background geometry, in this case the scene is placed within a Sphere. Textured geometry, an image is applied to the inside of the background Sphere to give the illusion

of a distant skyline.

Lighting, a single directional light is created to provide depth cues through rendering.

Geometry, a second smaller Sphere is placed within the scene.

Appearance, the smaller Sphere has an Appearance and Material associated with it that

interacts with the directional light to produce a shaded, colored effect.

Animation, a PositionInterpolator behavior is attached to the smaller Sphere to move it left and right using a complex time function (Alpha).

For instructions on running the examples that accompany the book please refer to appendix A.

To produce a comparable example using basic OpenGL would require many hundreds of lines of code. You can quickly see the benefits of a Java 3D’s higher−level of scene description—the scenegraph.

From SimpleTest.java

import java.applet.Applet;
import javax.media.j3d.*;
import javax.vecmath.*;
import com.sun.j3d.utils.geometry.*;
import com.sun.j3d.utils.universe.*;
import com.sun.j3d.utils.image.TextureLoader;
/*
* This example builds a simple Java 3D application using the
* Sun utility classes: MainFrame and SimpleUniverse.
* The example displays a moving sphere, in front of a
* background image. It uses a texture image and one light
* to increase the visual impact of the scene.
*/
public class SimpleTest extends Applet
{
/*
* Create a simple Java 3D environment containing:
* a sphere (geometry), a light,background geometry
* with an applied texture, and a behavior that will
* move the sphere along the X−axis.
*/
public SimpleTest()
{
// create the SimpleUniverse class that will
// encapsulate the scene that we are building.
// SimpleUniverse is a helper class (utility)
// from SUN that is included with the core Java 3D
// distribution.
SimpleUniverse u = new SimpleUniverse();
// create a BranchGroup. A BranchGroup is a node in
// a Tree data structure that can have child nodes
BranchGroup bgRoot = new BranchGroup();
// create the Background node and add it to the SimpleUniverse
u.addBranchGraph( createBackground() );
// create the behaviors to move the geometry along the X−axis.
// The behavior is added as a child of the bgRoot node.
// Anything added as a child of the tg node will be effected by the
// behavior (will be moved along the X−axis).
TransformGroup tg = createBehaviors( bgRoot );
// add the Sphere geometry as a child of the tg
// so that it will be moved along the X−axis.
tg.addChild( createSceneGraph() );
// because the sphere was added at the 0,0,0 coordinate
// and by default the viewer is also located at 0,0,0
// we have to move the viewer back a little so that
// she can see the scene.
u.getViewingPlatform().setNominalViewingTransform();
// add a light to the root BranchGroup to illuminate the scene
addLights( bgRoot );
// finally wire everything together by adding the root
// BranchGroup to the SimpleUniverse
u.addBranchGraph( bgRoot );
}
/*
* Create the geometry for the scene. In this case
* we simply create a Sphere
* (a built−in Java 3D primitive).
*/
public BranchGroup createSceneGraph()
{
// create a parent BranchGroup node for the Sphere
BranchGroup bg = new BranchGroup();
// create an Appearance for the Sphere.
// The Appearance object controls various rendering
// options for the Sphere geometry.
Appearance app = new Appearance();
// assign a Material to the Appearance. For the Sphere
// to respond to the light in the scene it must have a Material.
// Assign some colors to the Material and a shininess setting
// that controls how reflective the surface is to lighting.
Color3f objColor = new Color3f(0.8f, 0.2f, 1.0f);
Color3f black = new Color3f(0.0f, 0.0f, 0.0f);
app.setMaterial(new Material(objColor, black, objColor, black,
80.0f));
// create a Sphere with a radius of 0.1
// and associate the Appearance that we described.
// the option GENERATE_NORMALS is required to ensure that the
// Sphere responds correctly to lighting.
Sphere sphere = new Sphere( 0.1f, Primitive.GENERATE_NORMALS,
app );
// add the sphere to the BranchGroup to wire
// it into the scene.
bg.addChild( sphere );
return bg;
}
/*
* Add a directional light to the BranchGroup.
*/
public void addLights( BranchGroup bg )
{
// create the color for the light
Color3f color = new Color3f( 1.0f,1.0f,0.0f );
// create a vector that describes the direction that
// the light is shining.
Vector3f direction = new Vector3f( −1.0f,−1.0f,−1.0f );
// create the directional light with the color and direction
DirectionalLight light = new DirectionalLight( color, direction );
// set the volume of influence of the light.
// Only objects within the Influencing Bounds
// will be illuminated.
light.setInfluencingBounds( getBoundingSphere() );
// add the light to the BranchGroup
bg.addChild( light );
}
/*
* Create some Background geometry to use as
* a backdrop for the application. Here we create
* a Sphere that will enclose the entire scene and
* apply a texture image onto the inside of the Sphere
* to serve as a graphical backdrop for the scene.
*/
public BranchGroup createBackground()
{
// create a parent BranchGroup for the Background
BranchGroup backgroundGroup = new BranchGroup();
// create a new Background node
Background back = new Background();
// set the range of influence of the background
back.setApplicationBounds( getBoundingSphere() );
// create a BranchGroup that will hold
// our Sphere geometry
BranchGroup bgGeometry = new BranchGroup();
// create an appearance for the Sphere
Appearance app = new Appearance();
// load a texture image using the Java 3D texture loader
Texture tex = new TextureLoader( "back.jpg", this).getTexture();
// apply the texture to the Appearance
app.setTexture( tex );
// create the Sphere geometry with radius 1.0.
// we tell the Sphere to generate texture coordinates
// to enable the texture image to be rendered
// and because we are *inside* the Sphere we have to generate
// Normal coordinates inwards or the Sphere will not be visible.
Sphere sphere = new Sphere( 1.0f,
Primitive.GENERATE_TEXTURE_COORDS |
Primitive.GENERATE_NORMALS_INWARD, app );v
// start wiring everything together,
// add the Sphere to its parent BranchGroup.
bgGeometry.addChild( sphere );
// assign the BranchGroup to the Background as geometry.
back.setGeometry( bgGeometry );
// add the Background node to its parent BranchGroup.
backgroundGroup.addChild( back );
return backgroundGroup;
}
/*
* Create a behavior to move child nodes along the X−axis.
* The behavior is added to the BranchGroup bg, whereas
* any nodes added to the returned TransformGroup will be
* effected by the behavior.
*/
public TransformGroup createBehaviors( BranchGroup bg )
{
// create a TransformGroup.
//
// A TransformGroup is a Group node (can have children)
// and contains a Transform3D member.
//
// The Transform3D member contains a 4x4 transformation matrix
// that is applied during rendering to all the TransformGroup's
// child nodes. The 4x4 matrix can describe:
// scaling, translation and rotation in one neat package!
// enable the TRANSFORM_WRITE capability so that
// our behavior code can modify it at runtime.
TransformGroup objTrans = new TransformGroup();
objTrans.setCapability(TransformGroup.ALLOW_TRANSFORM_WRITE);
// create a new Transform3D that will describe
// the direction we want to move.
Transform3D xAxis = new Transform3D();
// create an Alpha object.
// The Alpha object describes a function against time.
// The Alpha will output a value that ranges between 0 and 1
// using the time parameters (in milliseconds).
Alpha xAlpha = new Alpha( −1,
Alpha.DECREASING_ENABLE |
Alpha.INCREASING_ENABLE,
1000,
1000,
5000,
1000,
1000,
10000,
2000,
4000 );
// create a PositionInterpolator.
// The PositionInterpolator will modify the translation components
// of a TransformGroup's Transform3D (objTrans) based on the output
// from the Alpha. In this case the movement will range from
// −0.8 along the X−axis with Alpha=0 to X=0.8 when Alpha=1.
PositionInterpolator posInt = new PositionInterpolator( xAlpha,
objTrans,
xAxis, −0.8f, 0.8f );
// set the range of influence of the PositionInterpolator
posInt.setSchedulingBounds( getBoundingSphere() );
// wire the PositionInterpolator into its parent
// TransformGroup. Just like rendering nodes behaviors
// must be added to the scenegraph.
objTrans.addChild( posInt );
// add the TransformGroup to its parent BranchGroup
bg.addChild( objTrans );
// we return the TransformGroup with the
// behavior attached so that we can add nodes to it
// (which will be effected by the PositionInterpolator).
return objTrans;
}
/*
* Return a BoundingSphere that describes the
* volume of the scene.
*/
BoundingSphere getBoundingSphere()
{
return new BoundingSphere( new Point3d(0.0,0.0,0.0), 200.0 );
}
/*
* main entry point for the Application.
*/
public static void main(String[] args)
{
SimpleTest simpleTest = new SimpleTest();
}
}

Ok good luck, See you in next tutorial