Virtual Reality Development Using Java3d

1
Virtual Reality Development Using Java3d

• John Hopf
• cisjph_at_cs.unisa.edu.au

2
This Lecture

• Outline the hardware that we will be using this
  semester in the VR Lab
• Introduce some basic concepts of Java3d
  programming
• Only the basics
• More resources on web
• Outline the software we will be using this
  semester
• Large
• Only going through code youll need to change
• Change any others and youre on your own

3
VR Laboratory PCs

• SGI machines
• Organising space on Bullwinkle
• Develop models with Cosmo Worlds
• Has Java3d so can develop and test
• Nice big monitors
• Two desktop windows machines
• Itchy on south end P4 1.8GHz GF3
• Scratchy on north end P4 1.9GHz GF4
• Mainly for testing with the trackers
• Logging on

4
The Polhemus Trackers

• Reflect real movement in virtual world
• Polhemus trackers
• Use magnetic fields
• Transmitter on ceiling mounting is important
• Used to track position of receivers boresight
• Gets Heading, Pitch, Roll, X, Y, Z data
• Itchy Fasttrak with four receivers
• Scratchy Isotrak2 with two receivers

5
Tracker Output

• Translation and rotation
• X,Y,Z co-ordinates are in centimeters units
• Heading, Pitch, Roll are in degrees units
• Heading left/right
• Pitch up/down
• Roll side to side
• Take this data and apply it to the view and hand
  avatar

6
Hand Controllers

• Controlling the hand in the virtual world
• Joystick handle with 5 buttons
• Buttons can be programmed for user defined
  functionality
• Mounted with a receiver to track hand movement
• Itchy has two and Scratchy has one
• Connected through a magic box to serial port

7
Head Mount Display

• So you can see without facing the monitor
• VR goggles mounted on a welding helmet
• For comport and adjustment
• Goggles display 1024x768 pixels
• Connected to TV out of PC video card
• A receiver is also mounted on the helmet to track
  head movement

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Further Information

• Visit the Java3d resources web page
• http//www.cis.unisa.edu.au/cisjph/vr/
• Provides Java API software required
• Instructions for installation
• Information about using equipment
• Contains code and updates for bug
  fixes/improvements visit regularly
• Software on CD

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Introducing Java3d

• A Java extension For 3D Programming
• Many platforms windows, unix, SGI
• OpenGL and DirectX
• This only an introduction
• Essential reading
• Getting Started With Java3d From Sun
• Essential Java3d By Ian Palmer

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How The World Is Presented

• The World Is Displayed As An Applet
• Currently set to 1020 x 760 to fill the screen
• The World is placed on a Canvas3D which is a
  subclass of Canvas
• The Canvas3D is placed on the Applet
• The Virtual Universe is then set to the Canvas3D

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Java3d Program Structure

• Java3d uses a scene graph concept

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Code To Create Our World

• Instantiate The SimpleUniverse Class
• Creates a simple Universe
• Includes a default locale
• Includes a default view branch
• Create The Content Branch And Add It To The
  SimpleUniverse

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Modifying The View Branch

• Defines how the scene is displayed
• Default from the SimpleUniverse
• Can get the viewPlatform to modify it
• We get the TransformGroup can use Transform3D
• Changing the view
• Eye position of the eye
• Centre a point we look at
• Up vector pointing to up location
• Dont need to change much else

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Creating The Content Branch

• The branch you need to change
• Defines what the scene looks like
• Objects
• Lighting
• Behaviour
• Contains a BranchGroup instance
• Objects and lights are added to this instance
• Use the createSceneGraph() method

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Creating Objects

• Objects to provide the look of the world
• Two possible ways
• Use Java3d
• Use a 3rd party tool to create objects
• Java3d looks better but is harder
• Looks vs. time
• Textures and lighting
• Your choice

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Java3d Objects

• Can combine several later on
• Create A Shape3D
• Define Geometry usually vertices of faces
• Define Appearance colour and texturing
• Basic shapes are available (cubes/spheres)
• Geometry Best Defined Using Geometry Arrays
• QuadArray or TriangleArray
• Appearance Is Defined In An Instance Of The
  Appearance Class

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Defining Geometry

• As said we use a geometry array
• Define faces
• Quadrilaterals or Triangles
• Co-ordinates of points
• Define faces
• Use a float array
• Three points per vertice

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Example Defining A Cube

• Use The QuadArray Class
• A cube contains 6 quadrilateral faces
• Need to specify 24 vertices
• Create A float Array For Coordinates
• Create A Default Appearance Object
• Create A Shape3D object

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Code To Create A Cube

• Shape3D buildCube()
• float cubeFaces
• 1.0f, -1.0f, 1.0f, 1.0f, 1.0f, 1.0f,
  -1.0f, 1.0f, 1.0f, -1.0f, -1.0f, 1.0f,
• -1.0f, -1.0f, -1.0f, -1.0f, 1.0f, -1.0f,
  1.0f, 1.0f, -1.0f, 1.0f, -1.0f, -1.0f,
• 1.0f, -1.0f, -1.0f, 1.0f, 1.0f, -1.0f,
  1.0f, 1.0f, 1.0f, 1.0f, -1.0f, 1.0f,
• -1.0f, -1.0f, 1.0f, -1.0f, 1.0f, 1.0f,
  -1.0f, 1.0f, -1.0f, -1.0f, -1.0f, -1.0f,
• 1.0f, 1.0f, 1.0f, 1.0f, 1.0f, -1.0f,
  -1.0f, 1.0f, -1.0f, -1.0f, 1.0f, 1.0f,
• -1.0f, -1.0f, 1.0f, -1.0f, -1.0f, -1.0f,
  1.0f, -1.0f, -1.0f, 1.0f, -1.0f, 1.0f
• QuadArray cubeData new QuadArray(24,
  QuadArray.COORDINATES)
• cubeData.setCoordinates(0, cubeFaces)
• Appearance app new Appearance()
• return new Shape3D(cubeData, app)

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What Does It Look Like?

• Doesnt Look Nice
• It Uses A Default Appearance
• No Lighting

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Appearance

• Use The Appearance Class
• Control colour
• Control textures
• Others for you to try
• Will discuss colour after lighting
• Images Show Coloured And Textured Cubes

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Texturing Objects

• Apply textures to the Appearance object
• Texture Comes From A File
• JPEG or GIF not too big
• Keep images in the images directory
• Need A Texture2D Instance
• Use TextureLoader to load the texture
• Use ImageComponent2D to get the image
• Create Texture2D Instance
• Add texture to appearance instance

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Code That Adds A Texture To An Appearance

• protected Appearance DefineAppearance()
• //Load the texture from the external image file
• TextureLoader textLoad new TextureLoader("house
  brick.jpg", this)
• ImageComponent2D textImage textLoad.getImage()
  
• //Create a two dimensional texture
• Texture2D texture new Texture2D(Texture2D.BASE_
  LEVEL, Texture.RGB,
• textImage.getWidth(), textImage.getHeight())
• //Set the texture from the image loaded
• texture.setImage(0, textImage)
• //Create the appearance that will use the
  texture
• Appearance app new Appearance()
• app.setTexture(texture)
• TextureAttributes textAttr new
  TextureAttributes()
• textAttr.setTextureMode(TextureAttributes.REPLACE
  )
• app.setTextureAttributes(textAttr)
• return app

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Adding Shape3d To The World

• Have To Add To A Transform Group
• Can add more than one shape3d to the group
• Table 4 legs and a table top
• Create A Transform3D Object For Translation And
  Rotation
• Translation Vector3f
• Rotation rotX, rotY, rotZ
• Add Transform3D to the Group
• Add TransformGroup To The Root Transform Group

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Using 3rd Party Tools - VRML

• Using Shape3D Is Laborious
• You can use VRML to specify objects
• We have a VRML loader for our world
• VRML97
• Many Graphics Apps Can Write VRML
• Windows ISB, Spazz3D, 3DS Max
• SGI Cosmo Worlds
• Easy To Manipulate Shapes And Apply Textures

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Getting VRML Into Java3D

• Create An Instance Of VRMLObject
• Filename without extension is argument
• Get the TransformGroup from the object
• Add to the rootTrans transform group
• Manipulating The Transform Group
• Create a Transform3D object
• Rotate and translate
• Set the Transform3D to the transform group

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Using The VRML Loader - Example

• VRMLObject table new VRMLObject
  ("coffee_table")
• TransformGroup tableTransformGroup
• table.getTransformGroup ()
• Transform3D tableTransform new Transform3D ()
• Vector3d tableLocation new Vector3d (0.0, 1.0,
  0.0)
• tableTransform.rotX(Math.PI/4)
• tableTransform.setTranslation (tableLocation)
• tableTransformGroup.setTransform
  (tableTransform)
• rootTrans.addChild (tableTransformGroup)

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Java3d Lighting - Lights

• Java3d Offers Four Types Of Lighting
• Ambient Light lights all objects equally
• Directional Light similar to sunlight
• Point Light a perfect light bulb
• Spot Light similar to a real life spotlight
• Limit The Influence Of The Light
• Isolate bedroom light to the bedroom
• setInfluencingBounds()
• Well go through each light type

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Ambient Light

• All Virtual Worlds Should Have One
• Left Is With And Right Is Without
• Color3f ambientColour new Color3f(0.2f, 0.2f,
  0.2f)
• AmbientLight ambientLight new
  AmbientLight(ambientColour)
• ambientLight.setEnable(true)
• ambientLight.setInfluencingBounds(new
  BoundingSphere(0.0,0.0,0.0), 10)
• Root.addChild(ambientLight)

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Directional Light Example

• Color3f lightColour new
• Color3f(1.0f,1.0f,1.0f)
• Vector3f lightDir new
• Vector3f(0.0f,-1.0f,-1.0f)
• DirectionalLight light new
• DirectionalLight( lightColour,lightDir)

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Directional Light Example 2

• Color3f lightColour new
• Color3f(1.0f,1.0f,1.0f)
• Vector3f lightDir new
• Vector3f(0.0f,1.0f,-1.0f)
• DirectionalLight light new
• DirectionalLight( lightColour,lightDir)

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Point Light

• Color3f lightColour new
• Color3f(1.0f, 1.0f, 1.0f)
• Point3f lightPosition new
• Point3f(1.5f, 1.5f, 1.5f)
• Point3f lightAtten new
• Point3f(1.0f, 0.0f, 0.0f)
• PointLight light new PointLight(lightColour,
  lightPosition, lightAtten)

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Spot Light

• Color3f blueColour new Color3f(0.0f, 0.0f,
  1.0f)
• Point3f bluePosition new Point3f(1.8f, 1.8f,
  1.8f)
• Point3f blueAtten new Point3f(1.0f, 0.0f,
  0.0f)
• Vector3f blueDir new Vector3f(-1.0f,-1.0f,-1.0f)
  
• SpotLight blueLight new SpotLight(blueColour,
• bluePosition,blueAtten,
• blueDir,(float)(Math.PI/2.0),0.0f)
• Color3f greenColour new Color3f(0.0f, 1.0f,
  0.0f)
• Point3f greenPosition new Point3f(0.0f, 0.0f,
  3.0f)
• Point3f greenAtten new Point3f(1.0f, 0.0f,
  0.0f)
• Vector3f greenDir new Vector3f(0.0f, 0.0f,
  -1.0f)
• SpotLight greenLight new SpotLight(greenColour,
• greenPosition,greenAtten,
• greenDir,(float)(Math.PI/2.0), 0.0f)

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Java3d Lighting - Surfaces

• The Material Class For Appearance
• ambientColor color under ambient light
• diffuseColor the light reflected
• specularColor for highlights like shine
• emissiveColor the light a surface emits
• shininess the level of shininess of the surface

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Surface Colour Example

• Appearance app new Appearance()
• Color3f ambientColour new Color3f(0.0f, 1.0f,
  0.0f)
• Color3f diffuseColour new Color3f(1.0f, 0.0f,
  0.0f)
• Color3f specularColour new Color3f(1.0f, 1.0f,
  1.0f)
• Color3f emissiveColour new Color3f(0.0f, 0.0f,
  0.0f)
• float shininess 20.0f
• app.setMaterial(new Material(
• ambientColour,emissiveColour,
  diffuseColour,specularColour, shininess))

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Specifying Behaviour

• We Have A Scene But Its Nothing Without
  Behaviour
• Behaviour provides life
• Behaviours Are Applied To Objects
• Need To Specify When It Happens
• Each Frame, Elapsed Time, Using Timers and others
• We Will Discuss Using Rotation Interpolators And
  The Behaviour Attached To The Hand

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Rotation Interpolators

• Default Rotation About The Y Axis
• Alpha Object Is Used For Timing
• Control speed/acceleration
• Control duration
• Produces a value between zero and one
• Ideal For Fans, Wheels and Other Rotating Objects

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Rotation Interpolator Y Axis

• Transform3D rotateCube new
• Transform3D( )
• TransformGroup rotationGroup new
• TransformGroup(rotateCube)
• Alpha rotationAlpha new
• Alpha(-1,Alpha.INCREASING_ENABLE,0,
• 0,4000,0,0,0,0,0)
• Transform3D yAxis new Transform3D()
• RotationInterpolator rotator new
• RotationInterpolator(rotationAlpha,
  rotationGroup, yAxis,
• 0.0f, (float) Math.PI2.0f)
• contentBranch.addChild(rotationGroup)
• rotationGroup.addChild(shape)
• rotationGroup.addChild(rotator)

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Rotation Interpolator - X Axis

• Transform3D rotateCube new
• Transform3D( )
• TransformGroup rotationGroup new
• TransformGroup(rotateCube)
• Alpha rotationAlpha new
• Alpha(-1,Alpha.INCREASING_ENABLE,0,0,
• 4000,0,0,0,0,0)
• Transform3D yAxis new Transform3D()
• yAxis.rotZ(Math.PI/2)
• RotationInterpolator rotator new
• RotationInterpolator(rotationAlpha,
  rotationGroup, yAxis,
• 0.0f, (float) Math.PI2.0f)
• contentBranch.addChild(rotationGroup)
• rotationGroup.addChild(shape)
• rotationGroup.addChild(rotator)

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Rotation Interpolator Z Axis

• Transform3D rotateCube new
• Transform3D( )
• TransformGroup rotationGroup new
• TransformGroup(rotateCube)
• Alpha rotationAlpha new
• Alpha(-1,Alpha.INCREASING_ENABLE,0,0,
• 4000,0,0,0,0,0)
• Transform3D yAxis new Transform3D()
• yAxis.rotX(Math.PI/2)
• RotationInterpolator rotator new
• RotationInterpolator(rotationAlpha,
  rotationGroup, yAxis,
• 0.0f, (float) Math.PI2.0f)
• contentBranch.addChild(rotationGroup)
• rotationGroup.addChild(shape)
• rotationGroup.addChild(rotator)

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Creating An Alpha

• Number of loops -1 indicates this loops
  infinitely
• Increasing or decreasing
• The time in milliseconds after system start up
  until the behaviour starts
• The time after the trigger time that the alpha
  values are generated
• How long it takes for the value of alpha to go
  from 0 to 1
• Acceleration
• Delay until restart
• The remaining 3 arguments are used for decreasing
  alpha.

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Where Are We Now?

• We Know How To Build A Scene
• We know how to add objects VRML is easier
• We know what lighting we can use
• We know how to attach behaviours to objects
• Now We Can Discuss How To Handle Interactions
  Using The Hand

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The Hand Behaviour

• In System We Have A Behaviour For The Hand That
  Fires On Every Frame
• Extends The Behavior Class
• Need to implement initialize()
• Need to implement processStimulus()
• Need To Make Changes To This Behaviour For
  Hand/World Interaction
• Rotation And Translation From Tracker
• Data Received From Button States

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The Hand Behaviour

• Five Buttons Available For Interaction
• Trigger is to pick see code
• Middle is to fly see code
• Left is to strafe see code
• Right is to strafe see code
• Side see code
• Change The Last 3 Be Creative!!

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Interactions With Objects

• Moving Objects Is Already Implemented
• What About Other Interactions
• A light switch
• A Door
• We Need To Differentiate Certain Objects From
  General Ones

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Allowing Objects To Be Picked

• You Can Specify Which Objects Are Sensitive To
  Hand Touches
• Use the setCollidable method
• You can set your own capabilities if you wish

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Interactions With Objects

• Identifying Specific Objects
• Can use the setUserData() method
• How can we access other objects
• Pass Necessities To HandBehaviour
• Arrays of Transform Groups, Lights and Others
• Make sure you remember which objects are in what
  array elements

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Adding To The Object Array

• TransformGroup groups new TransformGroup1
• ...
• VRMLObject lghtswtch new VRMLObject
  ("lightswitch")
• TransformGroup lghtswtchTransformGroup
  lghtswtch.getTransformGroup ()
• Transform3D lghtswtchTransform new Transform3D
  ()
• Vector3d lghtswtchLocation new Vector3d (4.0,
  2.0, 0.0)
• lghtswtchTransform.setTranslation
  (lghtswtchLocation)
• lghtswtchTransformGroup.setTransform
  (lghtswtchTransform)
• setCollidable(lghtswtch)
• rootTrans.addChild (lghtswtchTransformGroup)
• groups0 lghtswtchTransformGroup

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Accessing Array Elements

• private void processDrag_ (int button)
• ...
• TransformGroup group getPickedObject_collision
  ()
• ...
• if (group groups0))
• processLightSwitchInteraction()
• ...
• private void processLightSwitchInteraction()
• lights0.setEnabled(true)

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Summary

• What Have We Covered Today
• Hardware we will be using
• How we have created our world following the scene
  graph concept Java3d follows
• How to create objects and add them to our world
• How to create lighting and adjust appearances of
  object
• How to give life to our world using behaviour
• How we can use the hand to interact with the world

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Recommendations

• Dont Leave Assignments To The Last Minute
• Two test machines and 40 students
• Make Use of your allocated testing time
• Dont Sacrifice Usability For Good Looks
• Use A Third Party VRML Editor To Create Objects
  And For Texturing
• Make A Scaled Floorplan Of The World