Introduction to Java 3D
1
1. Java 3D Overview
API for 3D applications
 Portable

2
Some Application Areas
 Scientific/Medical/Data
visualization
 Geographical information systems (GIS)
 Computer-aided design (CAD)
 Simulation
 Computer-aided education (CAE)
 Games
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The Java 3D API
 Packages
–
–
–
–
related to the Java 3D API:
Core classes: javax.media.j3d
Utility classes:
com.sun.j3d.utils
Math classes: javax.vecmath
AWT classes: javax.swing
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Introduction
 Elements
of the rendering
– Objects
– Camera/View
– Canvas/Screen
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Introduction
 Rendering
 Camera
/ objects may move in time…
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Scene Representation
 Scene
– Representation of elements in the virtual world
– How to represent?
– What to represent?
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The Virtual Universe
 Basics
 Scene
Graph
 Locales
 Content Branch
 View Branch
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2. What is a Scene Graph?
 scene
graph = tree-like
 stores,3D scene
 easier than OpenGL or DirectX.
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Scene Graph Symbols
Nodes and Node Components (objects)
Group =erase head
Arcs (object relationships)
Parent-child link
Leaf=cone head
Node Component
Reference
Other objects=block head
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Java3D’s SceneGraph
VitualUniverse
Locale
Root group
robot arm
BG
TG
TG
Group =
erase head
TG
TG
S
S
environment
BG
TG
base
sphere
view
S
bottom arm
S
up arm
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The Virtual Universe
Objectives
 Know
what a virtual universe and a scene
graph is.
 Understand the basic parts and elements of
a scene graph.
 Know the basic recipe for a Java 3D
program.
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Leaf=cone head
Content Branch
A Typical Scene Graph
View Branch
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The Virtual Universe
Basics
 A virtual
universe can be seen as a 1:1
representation of our own universe.
 Represent structures from astronomical to
subatomic.
– Floating point 3D space: 2^256 (!!) for each
x,y,z.
– Decimal point for 1 meter at 2^128
– There is one VU-instance only (Singleton).
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The Virtual Universe
Locales (1)
 How
to handle the huge extend of a virtual
universe efficiently?
 Our virtual universe contains at least one
Locale.
 The locale is a 3D-reference point inside the
virtual universe.
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The Virtual Universe
Locales (2)
Standard Locale resides at (0,0,0) in the VU.
 We can have several Locales, eg:

– One as reference point of the swiss coordinate system
(located in Bordeaux, France).
– A second as the architects reference point of a building
plan.
– The both are related, but depending on the point of
view it is more convenient (and precise) to work with
one or the other.
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The Virtual Universe
Content Branch (1)
 Contains
all „visible“ objects of our scene.
 Contains all transformations for those
objects (displacement, animation, ...).
 We distinguish between group nodes and
leaf nodes (see following slide).
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The Virtual Universe
Content Branch (2)
 The
most common
object types
Branch
Group
...
Transform
Group
...
Appearance
Shape3D
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VirtualUniverse
The Virtual Universe
Scene Graph (1)
Locale
 Scene
Graph is the graphical
representation of the objects in
our VU.
 Directed Acyclic Graph (Tree)
– Nodes, arcs, parents, childs,
leaves, references and other
objects.
NodeComponent
Group
Link
Leaf
Reference
Other objects
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The Virtual Universe
Scene Graph (2)
 A Java
3D program may have more objects
than those in the scene graph.
 A scene graph drawing is the correct
documentation for the 3D part of a
Java 3D program.
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The Virtual Universe
View Branch
The Canvas3D will be
inserted in our application or
applet -> most important!
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The Virtual Universe
Recipe for a simple Program
1.
2.
3.
4.
Create a Frame & a
Canvas3D instance
Create a SimpleUniverse
Construct the content branch.
Insert the content branch into the Locale
of the SimpleUniverse.
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Hello World
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Hello World
Source Code
public class HelloJava3Da extends Applet {
public HelloJava3Da() {
setLayout(new BorderLayout());
Canvas3D canvas3D = new Canvas3D(null);
add("Center", canvas3D);
SimpleUniverse simpleU = new SimpleUniverse(canvas3D);
simpleU.getViewingPlatform().setNominalViewingTransform();
BranchGroup scene = createSceneGraph();
simpleU.addBranchGraph(scene);
}
public BranchGroup createSceneGraph() {
BranchGroup objRoot = new BranchGroup();
objRoot.addChild(new ColorCube(0.4));
return objRoot;
}
public static void main(String[] args) {
Frame frame = new MainFrame(new HelloJava3Da(), 256, 256);
}
}
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Hello World
Class Diagram of HelloJava3D
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Hello World
What happens when running?
while (true) {
Process input
Perform Behaviours //none at the moment
Traverse scene graph and render visual objects
if (request to exit) break
}
Cleanup and exit
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Scene Graph
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Java3D (cont.)
• The scene graph is a tree
• Elements of the scene that
have some data component,
such as viewable objects, light
sources, camera locations and
so forth are contained in the
graph nodes.
From: “The Java 3D Tutorial” by Dennis J Bouvier at java.sun.com/products/java-media/3D/collateral
and
http://www.itk.ilstu.edu/faculty/javila/ITk356/Java3D/scene_graph_basics.htm
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Symbols representing Scene Graph Objects:
Virtual Universe (V)
Locale (L)
Group (B or T)
Leaf (Lf)
Node Component (N)
Other Objects
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Scene Graph Viewing Objects
Canvas3D, Screen3D,
View, PhysicalBody,
PhysicalEnvironment.
From: “The Java 3D Tutorial” by Dennis J Bouvier at java.sun.com/products/java-media/3D/collateral
and
http://www.itk.ilstu.edu/faculty/javila/ITk356/Java3D/scene_graph_basics.htm
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Java3D (cont.)
Terminology
The renderer
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Code (create robot arm)





public void init() // applet’s init() function
{
setLayout(new BorderLayout());
GraphicsConfiguration config =
SimpleUniverse.getPreferredConfiguration();
Canvas3D c = new Canvas3D(config);
add("Center", c);



// create simple universe( camera, lights, ...)
u = new SimpleUniverse(c);


// This will move the ViewPlatform back a bit so the
// objects in the scene can be viewed.
u.getViewingPlatform().setNominalViewingTransform();



viewTrans =
u.getViewingPlatform().getViewPlatformTransform();
// Create a robot arm
createSceneGraph();
// add root group
u.addBranchGraph(rootGroup);







}
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














public void createSceneGraph()
{
// create root
rootGroup = new BranchGroup();
rootTrans = new TransformGroup();
rootTrans.setCapability(TransformGroup.ALLOW_TRANSFORM_READ);
rootTrans.setCapability(TransformGroup.ALLOW_TRANSFORM_WRITE);
// create bounds
BoundingSphere bounds =
new BoundingSphere(new Point3d(0.0,0.0,0.0), 100.0);
// create Appearance
Appearance greenLook = new Appearance();
ColoringAttributes greenColorAttr = new ColoringAttributes();
greenColorAttr.setColor(new Color3f(0.0f,1.0f,0.0f));
greenLook.setColoringAttributes(greenColorAttr);




// create Sphere
sphereTrans = new TransformGroup();
sphere = new Sphere(0.1f,redLook);

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



// transform sphere
Transform3D sphereT3d = new Transform3D();
sphereT3d.setTranslation(new Vector3f(0.5f,0.0f,0.0f));
sphereTrans.setTransform(sphereT3d);




// add sphere into scenegraph
sphereTrans.addChild(sphere);
rootTrans.addChild(sphereTrans);




// create arm
…..
} // end of createSceneGraph()
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3. A Java 3D Skeleton
 All
our Java 3D programs embed a scene
inside a JPanel, which is part of a JFrame
– this allows Swing GUI controls to be utilized
along side the Java 3D panel (if necessary)
 We
will develop an example called
Checkers3D during the course of these
slides.
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Checkers3D
 The
scene consists of
– a dark green and blue tiled
surface (and red center)
– labels along the X and Z axes
– a blue background
– a floating sphere lit from two different
directions
– the user (viewer) can move through the scene
by moving the mouse
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Checkers3D.java
public class Checkers3D extends JFrame
{ public Checkers3D()
{ super("Checkers3D");
Container c = getContentPane();
c.setLayout( new BorderLayout() );
WrapCheckers3D w3d = new WrapCheckers3D();
// panel holding the 3D scene
c.add(w3d, BorderLayout.CENTER);
setDefaultCloseOperation( JFrame.EXIT_ON_CLOSE );
pack();
setResizable(false);
// fixed size display
show();
} // end of Checkers3D()
public static void main(String[] args)
{ new Checkers3D(); }
} // end of Checkers3D class
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Scene Graph for Checkers3D
view branch
not shown
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Building the Scene Graph
 The VirtualUniverse, Locale,
and view
branch graph often have the same structure
across different applications
– programmers usually create them with the
SimpleUniverse utility class
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WrapChecker3D Constructor
private SimpleUniverse su;
private BranchGroup sceneBG; // for content branch
private BoundingSphere bounds;
:
public WrapCheckers3D()
{ setLayout( new BorderLayout() );
setOpaque( false );
setPreferredSize( new Dimension(PWIDTH, PHEIGHT));
GraphicsConfiguration config =
SimpleUniverse.getPreferredConfiguration();
Canvas3D canvas3D = new Canvas3D(config);
add("Center", canvas3D);
canvas3D.setFocusable(true);
canvas3D.requestFocus();
su = new SimpleUniverse(canvas3D);
:
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createSceneGraph();
initUserPosition();
// set user's viewpoint
orbitControls(canvas3D);
// controls for moving the viewpoint
su.addBranchGraph( sceneBG );
} // end of WrapCheckers3D()
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createSceneGraph()
private void createSceneGraph()
// initilise the scene below sceneBG
{
sceneBG = new BranchGroup();
bounds = new BoundingSphere(new Point3d(0,0,0),
BOUNDSIZE);
lightScene();
// add the light
addBackground();
// add the sky
sceneBG.addChild( new CheckerFloor().getBG() );
// add the floor
floatingSphere();
// add the floating sphere
sceneBG.compile();
// fix the scene
} // end of createSceneGraph()
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1. Checkers3D Again
 The
scene consists of
– a dark green and blue tiled
surface (and red center)
– labels along the X and Z axes
– a blue background
– a floating sphere lit from two different
directions
– the user (viewer) can move through the scene
by moving the mouse
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Scene Graph for Checkers3D
view branch
not shown
44
WrapChecker3D Constructor
private SimpleUniverse su;
private BranchGroup sceneBG; // for content branch
private BoundingSphere bounds;
:
public WrapCheckers3D()
{ setLayout( new BorderLayout() );
setOpaque( false );
setPreferredSize( new Dimension(PWIDTH, PHEIGHT));
GraphicsConfiguration config =
SimpleUniverse.getPreferredConfiguration();
Canvas3D canvas3D = new Canvas3D(config);
add("Center", canvas3D);
canvas3D.setFocusable(true);
canvas3D.requestFocus();
su = new SimpleUniverse(canvas3D);
:
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createSceneGraph();
initUserPosition();
// set user's viewpoint
orbitControls(canvas3D);
// controls for moving the viewpoint
su.addBranchGraph( sceneBG );
} // end of WrapCheckers3D()
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createSceneGraph()
private void createSceneGraph()
// initilise the scene below sceneBG
{
sceneBG = new BranchGroup();
bounds = new BoundingSphere(new Point3d(0,0,0),
BOUNDSIZE);
lightScene();
// add the light
addBackground();
// add the sky
sceneBG.addChild( new CheckerFloor().getBG() );
// add the BranchGroup for the floor
floatingSphere();
// add the floating sphere
sceneBG.compile();
// fix the scene
} // end of createSceneGraph()
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2. The Floor
 The
floor is made of tiles created with the
our ColouredTiles class, and axis labels
made with the Text2D utility class.
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Floor Branch of the Scene Graph
floorBG
axisTG
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CheckerFloor Constructor
// constants for various colours
:
private BranchGroup floorBG;
public CheckerFloor()
// create tiles, add origin marker,
// then the axes labels
{
ArrayList blueCoords = new ArrayList()
ArrayList greenCoords = new ArrayList();
floorBG = new BranchGroup();
:
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boolean isBlue;
for(int z = -FLOOR_LEN/2;
z <= (FLOOR_LEN/2)-1; z++) {
isBlue = (z%2 == 0)? true : false;
// set colour for new row
for(int x = -FLOOR_LEN/2;
x <= (FLOOR_LEN/2)-1; x++) {
if (isBlue)
createCoords(x, z, blueCoords);
else
createCoords(x, z, greenCoords);
isBlue = !isBlue;
}
}
:
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floorBG.addChild(
new ColouredTiles(blueCoords, blue) );
floorBG.addChild(
new ColouredTiles(greenCoords, green) );
addOriginMarker();
labelAxes();
} // end of CheckerFloor()
public BranchGroup getBG()
{ return floorBG; }
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private void createCoords(int x, int z,
ArrayList coords)
// Coords for a single blue or green square,
// its left hand corner at (x,0,z)
{
// points created in counter-clockwise order
Point3f p1 = new Point3f(x, 0.0f, z+1.0f);
Point3f p2 = new Point3f(x+1.0f,0.0f,z+1.0f);
Point3f p3 = new Point3f(x+1.0f, 0.0f, z);
Point3f p4 = new Point3f(x, 0.0f, z);
coords.add(p1); coords.add(p2);
coords.add(p3); coords.add(p4);
} // end of createCoords()
p3
p4
+x
p1
p2
+z
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ColouredTiles Class
 The ColouredTiles
class extends Shape3D,
and defines the geometry and appearance of
tiles with the same colour.
 The
geometry uses a QuadArray to represent
the tiles as a series of quadlilaterals.
v4
v1
v3 v8
v2 v5
v7
v6
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QuadArray Creation

The constructor is:
QuadArray(int vertexCount, int vertexFormat);

In ColouredTiles, the QuadArray plane is created
using:
plane = new QuadArray( coords.size(),
GeometryArray.COORDINATES |
GeometryArray.COLOR_3 );
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Filling the QuadArray
// coordinate data
int numPoints = coords.size();
Point3f[] points = new Point3f[numPoints];
coords.toArray( points );
// ArrayList-->array
plane.setCoordinates(0, points);
// colour data
Color3f cols[] = new Color3f[numPoints];
for(int i=0; i < numPoints; i++)
cols[i] = col;
plane.setColors(0, cols);
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Issues
 Counter-clockwise
specification of the
vertices for each quad
– makes the top of the quad its 'front'
 Ensure
that each quad is a convex, planar
polygon.
 Normals
or no normals?
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Unreflecting Colour

You can specify a shape's colour in three ways:
– in the shape's material

when the scene is illuminated
– in the shape's colouring attributes

used when the shape is unreflecting
– in the vertices of the shape's geometry

also for unreflecting shapes (used here)
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The Axes

Each axis value is a Text2D object, which specifies
the string, colour, font, point size, and font style:
Text2D message =
new Text2D("...", white, "SansSerif",
36, Font.BOLD );
// 36 point bold Sans Serif
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Positioning an Axis Value
TransformGroup axisTG = new TransformGroup();
Transform3D t3d = new Transform3D();
t3d.setTranslation( vertex );
// vertex is the position for the label
axisTG.setTransform(t3d);
axisTG.addChild( message );
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Create a color cube
 Prompt
the user for an image, list unique
colors in the image and then
 Create a sphere for each color such that:
– The sphere has that color
– The sphere is positioned in 3space according to
its color
– The color space is an RGB space.
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