The use of the CollisionDetector
import java.awt.BorderLayout;
import java.awt.Button;
import java.awt.Frame;
import java.awt.Panel;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.util.Enumeration;
import javax.media.j3d.AmbientLight;
import javax.media.j3d.Appearance;
import javax.media.j3d.Behavior;
import javax.media.j3d.BoundingSphere;
import javax.media.j3d.Bounds;
import javax.media.j3d.BranchGroup;
import javax.media.j3d.Canvas3D;
import javax.media.j3d.DirectionalLight;
import javax.media.j3d.IndexedQuadArray;
import javax.media.j3d.Locale;
import javax.media.j3d.Material;
import javax.media.j3d.Node;
import javax.media.j3d.PhysicalBody;
import javax.media.j3d.PhysicalEnvironment;
import javax.media.j3d.Shape3D;
import javax.media.j3d.Transform3D;
import javax.media.j3d.TransformGroup;
import javax.media.j3d.View;
import javax.media.j3d.ViewPlatform;
import javax.media.j3d.VirtualUniverse;
import javax.media.j3d.WakeupCriterion;
import javax.media.j3d.WakeupOnCollisionEntry;
import javax.media.j3d.WakeupOnCollisionExit;
import javax.media.j3d.WakeupOnCollisionMovement;
import javax.media.j3d.WakeupOr;
import javax.vecmath.Color3f;
import javax.vecmath.Point3d;
import javax.vecmath.Point3f;
import javax.vecmath.Vector3d;
import javax.vecmath.Vector3f;
import com.sun.j3d.utils.picking.behaviors.PickTranslateBehavior;
/**
* This class demonstrates the use of the CollisionDetector class to perform
* processing when objects collide. When this program is run the white cube can
* be selected and moved by dragging on it with the right mouse button. You
* should notice that there is a problem if the movable cube comes into contact
* with both of the static cubes at one time. A way round this is given in the
* SimpleCollision2 application.
*
* @see CollisionDetector
* @see SimpleCollision2
* @author I.J.Palmer
* @version 1.0
*/
public class SimpleCollision extends Frame implements ActionListener {
protected Canvas3D myCanvas3D = new Canvas3D(null);
protected Button exitButton = new Button("Exit");
protected BoundingSphere bounds = new BoundingSphere(new Point3d(0.0, 0.0,
0.0), 100.0);
/** Transform for the left cube. */
protected TransformGroup leftGroup;
/** Transform for the right cube */
protected TransformGroup rightGroup;
/**
* Transform for the movable cube. This has read, write and pick reporting
* capabilities enabled.
*/
protected TransformGroup moveGroup;
/** A transform to change the size of the movable cube. */
protected TransformGroup scaleGroup;
/** The left static cube. */
protected Shape3D leftCube;
/** The right static cube. */
protected Shape3D rightCube;
/** The movable cube that will collide with the other two cubes */
protected Shape3D moveCube;
/**
* This builds the view branch of the scene graph.
*/
protected BranchGroup buildViewBranch(Canvas3D c) {
BranchGroup viewBranch = new BranchGroup();
Transform3D viewXfm = new Transform3D();
viewXfm.set(new Vector3f(0.0f, 0.0f, 10.0f));
TransformGroup viewXfmGroup = new TransformGroup(viewXfm);
ViewPlatform myViewPlatform = new ViewPlatform();
PhysicalBody myBody = new PhysicalBody();
PhysicalEnvironment myEnvironment = new PhysicalEnvironment();
viewXfmGroup.addChild(myViewPlatform);
viewBranch.addChild(viewXfmGroup);
View myView = new View();
myView.addCanvas3D(c);
myView.attachViewPlatform(myViewPlatform);
myView.setPhysicalBody(myBody);
myView.setPhysicalEnvironment(myEnvironment);
return viewBranch;
}
/**
* This adds some lights to the content branch of the scene graph.
*
* @param b
* The BranchGroup to add the lights to.
*/
protected void addLights(BranchGroup b) {
Color3f ambLightColour = new Color3f(0.5f, 0.5f, 0.5f);
AmbientLight ambLight = new AmbientLight(ambLightColour);
ambLight.setInfluencingBounds(bounds);
Color3f dirLightColour = new Color3f(1.0f, 1.0f, 1.0f);
Vector3f dirLightDir = new Vector3f(-1.0f, -1.0f, -1.0f);
DirectionalLight dirLight = new DirectionalLight(dirLightColour,
dirLightDir);
dirLight.setInfluencingBounds(bounds);
b.addChild(ambLight);
b.addChild(dirLight);
}
/**
* Creates the content branch of the scene graph.
*
* @return BranchGroup with content attached.
*/
protected BranchGroup buildContentBranch() {
//First create a different appearance for each cube
Appearance app1 = new Appearance();
Appearance app2 = new Appearance();
Appearance app3 = new Appearance();
Color3f ambientColour1 = new Color3f(1.0f, 0.0f, 0.0f);
Color3f ambientColour2 = new Color3f(1.0f, 1.0f, 0.0f);
Color3f ambientColour3 = new Color3f(1.0f, 1.0f, 1.0f);
Color3f emissiveColour = new Color3f(0.0f, 0.0f, 0.0f);
Color3f specularColour = new Color3f(1.0f, 1.0f, 1.0f);
Color3f diffuseColour1 = new Color3f(1.0f, 0.0f, 0.0f);
Color3f diffuseColour2 = new Color3f(1.0f, 1.0f, 0.0f);
Color3f diffuseColour3 = new Color3f(1.0f, 1.0f, 1.0f);
float shininess = 20.0f;
app1.setMaterial(new Material(ambientColour1, emissiveColour,
diffuseColour1, specularColour, shininess));
app2.setMaterial(new Material(ambientColour2, emissiveColour,
diffuseColour2, specularColour, shininess));
app3.setMaterial(new Material(ambientColour3, emissiveColour,
diffuseColour3, specularColour, shininess));
//Create the vertex data for the cube. Since each shape is
//a cube we can use the same vertex data for each cube
IndexedQuadArray indexedCube = new IndexedQuadArray(8,
IndexedQuadArray.COORDINATES | IndexedQuadArray.NORMALS, 24);
Point3f[] cubeCoordinates = { new Point3f(1.0f, 1.0f, 1.0f),
new Point3f(-1.0f, 1.0f, 1.0f),
new Point3f(-1.0f, -1.0f, 1.0f),
new Point3f(1.0f, -1.0f, 1.0f), new Point3f(1.0f, 1.0f, -1.0f),
new Point3f(-1.0f, 1.0f, -1.0f),
new Point3f(-1.0f, -1.0f, -1.0f),
new Point3f(1.0f, -1.0f, -1.0f) };
Vector3f[] cubeNormals = { new Vector3f(0.0f, 0.0f, 1.0f),
new Vector3f(0.0f, 0.0f, -1.0f),
new Vector3f(1.0f, 0.0f, 0.0f),
new Vector3f(-1.0f, 0.0f, 0.0f),
new Vector3f(0.0f, 1.0f, 0.0f), new Vector3f(0.0f, -1.0f, 0.0f) };
int cubeCoordIndices[] = { 0, 1, 2, 3, 7, 6, 5, 4, 0, 3, 7, 4, 5, 6, 2,
1, 0, 4, 5, 1, 6, 7, 3, 2 };
int cubeNormalIndices[] = { 0, 0, 0, 0, 1, 1, 1, 1, 2, 2, 2, 2, 3, 3,
3, 3, 4, 4, 4, 4, 5, 5, 5, 5 };
indexedCube.setCoordinates(0, cubeCoordinates);
indexedCube.setNormals(0, cubeNormals);
indexedCube.setCoordinateIndices(0, cubeCoordIndices);
indexedCube.setNormalIndices(0, cubeNormalIndices);
//Create the three cubes
leftCube = new Shape3D(indexedCube, app1);
rightCube = new Shape3D(indexedCube, app2);
moveCube = new Shape3D(indexedCube, app3);
//Define the user data so that we can print out the
//name of the colliding cube.
leftCube.setUserData(new String("left cube"));
rightCube.setUserData(new String("right cube"));
//Create the content branch and add the lights
BranchGroup contentBranch = new BranchGroup();
addLights(contentBranch);
//Create and set up the movable cube's TransformGroup.
//This scales and translates the cube and then sets the
// read, write and pick reporting capabilities.
Transform3D moveXfm = new Transform3D();
moveXfm.set(0.7, new Vector3d(0.0, 2.0, 1.0));
moveGroup = new TransformGroup(moveXfm);
moveGroup.setCapability(TransformGroup.ALLOW_TRANSFORM_WRITE);
moveGroup.setCapability(TransformGroup.ALLOW_TRANSFORM_READ);
moveGroup.setCapability(TransformGroup.ENABLE_PICK_REPORTING);
//Create the left cube's TransformGroup
Transform3D leftGroupXfm = new Transform3D();
leftGroupXfm.set(new Vector3d(-1.5, 0.0, 0.0));
leftGroup = new TransformGroup(leftGroupXfm);
//Create the right cube's TransformGroup
Transform3D rightGroupXfm = new Transform3D();
rightGroupXfm.set(new Vector3d(1.5, 0.0, 0.0));
rightGroup = new TransformGroup(rightGroupXfm);
//Add the behaviour to allow us to move the cube
PickTranslateBehavior pickTranslate = new PickTranslateBehavior(
contentBranch, myCanvas3D, bounds);
contentBranch.addChild(pickTranslate);
//Add our CollisionDetector class to detect collisions with
//the movable cube.
CollisionDetector myColDet = new CollisionDetector(moveCube, bounds);
contentBranch.addChild(myColDet);
//Create the content branch hierarchy.
contentBranch.addChild(moveGroup);
contentBranch.addChild(leftGroup);
contentBranch.addChild(rightGroup);
moveGroup.addChild(moveCube);
leftGroup.addChild(leftCube);
rightGroup.addChild(rightCube);
return contentBranch;
}
/**
* Process the exit button action to exit the application.
*/
public void actionPerformed(ActionEvent e) {
if (e.getSource() == exitButton) {
dispose();
System.exit(0);
}
}
public SimpleCollision() {
VirtualUniverse myUniverse = new VirtualUniverse();
Locale myLocale = new Locale(myUniverse);
myLocale.addBranchGraph(buildViewBranch(myCanvas3D));
myLocale.addBranchGraph(buildContentBranch());
setTitle("SimpleWorld");
setSize(400, 400);
setLayout(new BorderLayout());
Panel bottom = new Panel();
bottom.add(exitButton);
add(BorderLayout.CENTER, myCanvas3D);
add(BorderLayout.SOUTH, bottom);
exitButton.addActionListener(this);
setVisible(true);
}
public static void main(String[] args) {
SimpleCollision sw = new SimpleCollision();
}
}
/**
* A simple collision detector class. This responds to a collision event by
* printing a message with information about the type of collision event and the
* object that has been collided with.
*
* @author I.J.Palmer
* @version 1.0
*/
class CollisionDetector extends Behavior {
/** The separate criteria used to wake up this beahvior. */
protected WakeupCriterion[] theCriteria;
/** The OR of the separate criteria. */
protected WakeupOr oredCriteria;
/** The shape that is watched for collision. */
protected Shape3D collidingShape;
/**
* @param theShape
* Shape3D that is to be watched for collisions.
* @param theBounds
* Bounds that define the active region for this behaviour
*/
public CollisionDetector(Shape3D theShape, Bounds theBounds) {
collidingShape = theShape;
setSchedulingBounds(theBounds);
}
/**
* This creates an entry, exit and movement collision criteria. These are
* then OR'ed together, and the wake up condition set to the result.
*/
public void initialize() {
theCriteria = new WakeupCriterion[3];
theCriteria[0] = new WakeupOnCollisionEntry(collidingShape);
theCriteria[1] = new WakeupOnCollisionExit(collidingShape);
theCriteria[2] = new WakeupOnCollisionMovement(collidingShape);
oredCriteria = new WakeupOr(theCriteria);
wakeupOn(oredCriteria);
}
/**
* Where the work is done in this class. A message is printed out using the
* userData of the object collided with. The wake up condition is then set
* to the OR'ed criterion again.
*/
public void processStimulus(Enumeration criteria) {
WakeupCriterion theCriterion = (WakeupCriterion) criteria.nextElement();
if (theCriterion instanceof WakeupOnCollisionEntry) {
Node theLeaf = ((WakeupOnCollisionEntry) theCriterion)
.getTriggeringPath().getObject();
System.out.println("Collided with " + theLeaf.getUserData());
} else if (theCriterion instanceof WakeupOnCollisionExit) {
Node theLeaf = ((WakeupOnCollisionExit) theCriterion)
.getTriggeringPath().getObject();
System.out.println("Stopped colliding with "
+ theLeaf.getUserData());
} else {
Node theLeaf = ((WakeupOnCollisionMovement) theCriterion)
.getTriggeringPath().getObject();
System.out.println("Moved whilst colliding with "
+ theLeaf.getUserData());
}
wakeupOn(oredCriteria);
}
}
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