Java 3D, GLUT input

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Java 3D, GLUT input
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Java 3D

• API for writing 3D graphics
• applications/applets
• can mix with regular Java, such as AWT events
• Write once, view anywhere
• Scene Graph
• tree data structure
• describes entire scene (Virtual Universe)

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Simple Scene Graph Example
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Assembling a Scene Graph

• Create a Canvas3D object
• Construct viewing branch graph (can use
  SimpleUniverse convenience utility)
• VirtualUniverse object
• high-resolution Locale object
• ViewPlatform object
• which references a View object
• which in turn references PhysicalBody,
• PhysicalEnvironment, and the earlier Canvas3D
  objects

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Assembling a Scene Graph

• Construct content branch graph
• for Geometry, Appearance, Behavior, etc.
• this branch graph can get quite complex
• Optionally compile branch graphs
• Insert both branch graphs into the Locale

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Terminology

• live
• attached to scene graph tree
• compiled into optimized format
• prior to attachment to main scene graph
• cannot undo compile !!!
• some actions rely upon live or compiled states
• for example, once live or compiled, capabilities
  cannot be changed

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SceneGraph Traversal

• Java 3D renderer chooses traversal order
• not restricted to left-to-right or top-to-bottom
• except for spatially bounded attributes, such as
  light sources, fog
• open to parallel processing

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The Java 3D Renderer

• starts running in an infinite loop
• conceptually performs the following operations
• while(true)
• Process input
• If (request to exit) break
• Perform Behaviors
• Traverse the scene graph
• and render visible objects
• Cleanup and exit

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Packages

• typical import statements
• import javax .media.j3d.
• import javax .vecmath .
• import com.sun.j3d. utils .applet. MainFrame
• import com.sun.j3d. utils .geometry. ColorCube
• import com.sun.j3d. utils .universe.
• import java .applet.Applet
• import java .awt.BorderLayout
• import java .awt.Frame
• import java .awt.event.

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General Java 3D Facts

• default SimpleUniverse virtual world
• coordinate system
• right-handed coordinate system
• back up several units in z
• look toward origin
• angles are always in radians
• most set() methods have corresponding get()
  methods
• physical world units are in meters

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SceneGraphObject class

• abstract class represents any scene graph
  component
• methods common to everything in scene graph
• controls object capabilities
• setCapability() method very useful
• enables operations to be allowed when live or
  compiled
• if already live or compiled , capability cannot
  be changed
• superclass for Node and NodeComponent classes

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Node

• superclass of Group and Leaf classes
• Node objects can be put directly into the scene
  graph
• NodeComponent objects cannot be in a scene graph
  tree, but can be referenced

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Leaf

• has no children
• may reference NodeComponent objects
• superclass for elements used in rendering
• such as geometry, lights, sounds
• Shape3D--important subclass

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Group

• may contain child node objects
• superclass of important BranchGroup and
  TransformGroup nodes
• addChild() method is used most often

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NodeComponent

• superclass for Geometry and Appearance classes
• and 14 other Java 3D classes
• Geometry may include coordinates, colors,
  normals, texture coordinates
• Appearance objects may specify color, texture
  parameters, culling, shading, etc.

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Hello3D Applet/Application

• static program rendering one 3D object

SimpleUniverse
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Hello3D.java Constructor

• // Scene graph constructed
• Hello3D()
• setLayout(new BorderLayout())
• Canvas3D c new Canvas3D(null)
• add("Center", c)
• BranchGroup scene createSceneGraph()
• SimpleUniverse u new SimpleUniverse(c)
• u.addBranchGraph(scene) // makes it live
• public static void main(String args)
• Frame frame
• new MainFrame(new Hello3D(), 256, 256)

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Create Hello3D Scene Graph

• public class Hello3D extends Applet
• public BranchGroup createSceneGraph()
• BranchGroup objRoot new BranchGroup()
• objRoot.addChild(new ColorCube())
• return objRoot

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Interaction

• Interaction is an important component of graphics
  applications
• Most modern APIs, such as OpenGL, doesnt support
  interaction directly (why?)
• We need additional libraries, such as GLUT, for
  device interaction

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Input Devices

• We can think about input devices in two ways

• Physical device that can be described by their
  real-world physical properties.
• (mouse, keyboard, joystick)

• Logical devices that is characterized by its
  high-level interface with the user program. It is
  an abstraction of device data.
• (functions, think of the windows device driver)

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Physical Device Types

• Keyboard
• Choice
• Locators

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Keyboard

• Returns character coders with specific meanings

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Choice

• Returns a choice that has been selected from a
  number of discrete options

- Button box - Function keypad
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Locator Devices

• Return a position and/or orientation

• Mouse
• Trackball
• Tablet
• Joystick
• Touch screen

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3D Input Devices

• Return 3D position and /or orientation
• Digitizer
• 3D Spaceball
• Glove
• Tracker

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3D Input Devices
Digitizer - 3D model
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3D Input Devices
3D Spaceball
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3D Input Devices
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3D Input Devices
Motion Tracker - Magnetic - Acoustic -
Inertial - Optical - GPS
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Logical Device

• Characterized from the perspective of user
  application program
• High-level interface with the user program
• An abstraction of device data

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Logical Device Types

• String
• Returns ASCII strings
• Locator
• Returns position and or orientation
• Pick
• Returns the identifier of object
• Choice
• Returns a choice that has been selected from a
  number of options
• Dial
• Return analog input (continuous control)
• Stroke
• Returns an array of locations

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Describe Input Device Behavior

• Ways to describe input device behavior
• Measure what the device returns to user program
• Trigger when the device returns those
  measurements

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Ways to Read Input Device

• Sample mode
• Request mode
• Event mode

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Sample Mode

• Hi, What is its input right now? Give me the
  data immediately!

Measure Process

• - No trigger needed
• Return immediately
• Prepare the data before function call

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Request Mode

• Do not return the measure until the device is
  triggered

Measure Process
Trigger Process

• - Wait for triggering
• Think of the C function call scanf()

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Event Mode

• Wait until a device is triggered and user does
  something

• Two asynchronous processes
• - Event generation (device trigger)
• User request (event query)
• Event generation and process are independent
• Multiple input devices

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Event Mode

• Lets think of the Windows event mechanism

• - Generate a event by a device trigger
• Place the event in the event queue
• Examine the event queue and process

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Event Mode

• Two Asynchronous Processes

Trigger Process
Event Queue
Measure Process
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Interactive GraphicsProgramming

• We will focus on
• Event-driven Input mode
• Callback mechanism to do event process
• GLUT programming

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Callback Functions

• Callback Function
• Routine to call when some event happens.
• e.g. mouse/keyboard, window changes, etc.
• GLUT uses a callback mechanism to do its event
  processing.

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Event-driven Input Programming

• Decide input events
• mouse, keyboard, window
• Write callback functions
• respond to each input event,
• Register callback functions
• tell the system to handle the event,
• Event processing loop
• Wait and process

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GLUT Event Callback Functions

• GLUT can handle the most commonly used input
  events
• Ex
• Key action
• Mouse action
• Idle (called when nothing else is going on)
• Window events (contents, resized or moved)

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Keyboard Event
Its called when a key is struck on the keyboard
glutKeyboardFunc ( keyboard_callback_func )
void keyboard_callback_func ( unsigned char key,
int x, int y ) switch (key)
case q exit (0)
break
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Mouse Event
Its called when a mouse button is
depressed/released
glutMouseFunc ( mouse_callback_func )

• void mouse_callback_func ( int button, int
  state, int x, int y )
• button which button is depressed/released.
• GLUT_LEFT_BUTTON, GLUT_MIDDLE_BUTTON,
  GLUT_RIGHT_BUTTON
• state action state.
• GLUT_DOWN, GLUT_UP
• x, y position

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Mouse Event
void mouse_callback_func ( int button, int
state, int x, int y ) if ( button
GLUT_LEFT_BUTTON state GLUT_DOWN )
exit (0)
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You Must Register Callback
void main (int argc, char argv)
glutDisplayFunc ( display ) //
display callback
glutReshapeFunc ( resize ) // window
resize glutKeyboardFunc ( key )
// keyboard callback
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Main Function
void main (int argc, char argv)
glutInit ( argc, argv )
glutInitDisplayMode (GLUT_SINGLE GLUT_RGB)
glutInitWindowSize (256, 256)
glutCreateWindow (My Program") myinit
()
glutDisplayFunc ( square )
// register callback
glutMainLoop ()
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OpenGL Initialization
void myinit (void) glClearColor (1.0,
1.0, 1.0, 0.0) // background
glMatrixMode(GL_PROJECTION)
glLoadIdentity() gluOrtho2D (0.0, 256.0,
0.0, 256.0) glMatrixMode(GL_MODELVIEW)
glClear(GL_COLOR_BUFFER_BIT) //
clear the window
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Display Callback Function
void square (void) typedef GLfloat
point2D2 point2D vertices4
100.0, 100.0,200.0, 100.0,200.0,
200.0,100.0, 200.0
glClear(GL_COLOR_BUFFER_BIT) // clear
the window glColor3f (0.0, 0.0, 1.0)
glBegin(GL_POLYGON) glVertex2fv
(vertices0) glVertex2fv
(vertices1) glVertex2fv
(vertices2) glVertex2fv
(vertices3) glEnd()
glFlush()
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What it Looks Like
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Add Interaction
void main (int argc, char argv)
glutInit ( argc, argv )
glutInitDisplayMode (GLUT_SINGLE GLUT_RGB)
glutInitWindowSize (256, 256)
glutCreateWindow (My Program") myinit
() glutKeyboardFunc ( keyboard_callback_func )
glutDisplayFunc ( square )
// register display callback glutMainLoop
()
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Keyboard Callback Function
void keyboard_callback_func ( unsigned char key,
int x, int y ) switch (key)
case q exit (0)
break case a // change
some display state break
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Idle Callbacks

• Use for animation and continuous update
• glutIdleFunc( idle )
• void idle( void )
• t dt
• glutPostRedisplay()

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How would we apply this?

• To Pong