Input Devices Introduction to OpenGL

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Input DevicesIntroduction to OpenGL
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Learning Objectives

• Survey of input devices
• Introduction to OpenGL
• First OpenGL program with Java bindings

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Input Devices

• Input devices
• Keyboards, button boxes, dials
• Mouse devices
• Trackballs and spaceballs
• Joysticks
• Data gloves
• Digitizers
• Image scanners
• Touch panels
• Light pens
• Voice systems

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Input Devices

• Keyboards, button boxes, dials
• Standard keyboard
• Alphanumeric
• Function keys
• Button boxset of input dials

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Input Devices

• Mouse devices
• Mechanical mouse
• One-button
• Rotating ball
• Two perpendicular shafts to capture rotation
• Optical mouse
• Optical sensor
• Laser
• Grid to detect movement
• Added widgets
• Buttons
• Trackball
• Thumbwheel.

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Input Devices

• Trackball
• A ball device that can be rotated with the
  fingers or palm of hand
• Spaceball
• Six degrees of freedom
• Does not move, detects strain placed on the ball
  by trying to move it.

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Input Devices

• Joystick
• A small, vertical lever mounted on a base
• Movable joystick measures motion
• Stationary (isometric) joystick measures strain.
• Data glove
• Used to grasp a virtual object
• Measures hand and finger position
• 2D or 3D
• Can also be used as input device to detect
  surface.

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Input Devices

• Digitizers
• Used for drawing, painting, or selecting
  positions
• Graphics tablet used to input 2D coordinates by
  activating a hand cursor or stylus at given
  positions on a flat surface
• Used to trace contours, select precise coordinate
  positions
• Hand held cursor
• Stylus
• Electromagnetic
• Grid of wires
• Electromagnetic pulses send an electrical signal
  in stylus or cursor
• Acoustic
• Sound waves to detect stylus position by
  microphones
• Can be 3D.
• Image scanners

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Input Devices

• Image scanners
• Used to store images on a computer
• Hand held
• Flatbed
• Drum.

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Input Devices

• Touch panels
• Select objects by the touch of a finger
• Optical
• Line of infrared light-emitting diodes (LED)
  along vertical and horizontal edges
• Interrupted when panel is touched
• Electrical
• Two transparent plates of material, one
  conducting, the other resistive
• Touch brings the plates to be in contact with one
  another, causing a voltage drop
• Measure the voltage drop
• Acoustical.
• Light pens

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Input Devices

• Light pens
• Pen-shaped device to select screen positions by
  detecting lights coming from points on the CRT
  screen
• Used to capture position of an object or select
  menu options.

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Input Devices

• Voice systems
• Speech recognition systems to recognize voice
  commands
• Used to activate menu options or to enter data
• Uses a dictionary from a particular user
  (learning system).

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Hard-copy Devices

• Hard-copy devices
• Plotters
• 2D moving pen with stationary paper
• 1D pen and 1D moving paper
• Printers
• Impact devices
• Inked ribbon
• Non impact devices
• Laser, ink-jet, xerographic, electrostatic,
  electrothermal.

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Graphics Software

• Graphics software
• Special purpose
• For non programmers
• CAD, CAM, painting, animation
• General programming packages
• Library of graphics functions
• C, C, Java,
• Picture components (lines, shapes, )
• Transformations (color, texture, shading,
  rotating, )

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Coordinate Representation

• Cartesian coordinates
• Modeling coordinates (local, master)in the
  reference frame of each object
• World coordinatesin the scene reference frame
• Viewing coordinatesview we want of a scene
• Normalized (device) coordinatesnormalized
  between 1 and 1 or 0 and 1
• Device coordinates (screen coordinates)

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Coordinate System
(from Donald Hearn and Pauline Baker)
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Introduction to OpenGL

• OpenGL
• First part of Silicon Graphics graphics
  workstations
• Became hardware independent in early 1990s
• Maintained by the OpenGL Architecture Review
  Board
• Developed for 3D scenes
• 2D scenes as projections where z-coordinate is 0.

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Important Concepts

• Three dimensional concepts
• Light-material interactions
• Transformations
• Modeling
• Interaction
• Rendering Algorithms
• ... and others

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OpenGL

• Graphics rendering API (Application Programmers
  Interface)
• Generation of high-quality color images composed
  of geometric and image primitives
• Window system independent
• Operating system independent
• Close to the hardware
• Algorithms and implementation are important

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Pipeline Model

• Close to hardware
• Easy to program
• Direct implementation of synthetic camera
• Image formation by computer is analogous to image
  formation by camera (or human)
• Specify viewer, objects, lights
• Let hardware/software form image (via projection)

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OpenGL Geometric Pipeline
State
ApplicationProgram
ModelView Transformation
Frame Buffer
Rasterization
Projection
Pixels
Vertices
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OpenGL as a Renderer

• Two operations (basically) in OpenGL
• Draw something
• Change the state of what or how OpenGL draws
• Geometric primitives
• Various kinds of points, lines, and polygons
• Image Primitives
• Images and bitmaps
• Separate pipeline for images and geometry
• Linked through texture mapping
• Rendering depends on the state of
• Colors, materials, light sources, etc.

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OpenGL Architecture
Upper pipeline is for geometric, vector-based
primitives.
Lower pipeline is for pixel-based,
image primitives.
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OpenGL and the Windowing System

• OpenGL is concerned only with rendering
• It is window system independent
• No input functions
• OpenGL must interact with the underlying OS and
  windowing system
• Need minimal interface which may be system
  dependent
• Done through additional libraries AGL, GLX, WGL

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GLU and GLUT

• GLU (OpenGL Utility Library)
• Part of OpenGL
• Provides NURBS (splines), etc.
• GLUT (OpenGL Utility Toolkit)
• A portable windowing API
• Not officially part of OpenGL
• Extremely useful for helping to create images
  quickly without worrying about the underlying
  windowing system being used

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OpenGL and Related APIs
application program
OpenGL Motif widget or similar
GLUT
GLX, AGLor WGL
GLU
GL
X, Win32, Mac O/S
software and/or hardware
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OpenGL Geometric Primitives

• All geometric primitives are specified by vertices

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OpenGL Command Formats
glVertex3fv( v )
Number of components
Data Type
Vector
b - byte ub - unsigned byte s - short us -
unsigned short i - int ui - unsigned int f -
float d - double
omit v for scalar form glVertex2f( x, y )
2 - (x,y) 3 - (x,y,z) 4 - (x,y,z,w)
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Specifying Geometric Primitives

• Primitives are specified using
• glBegin( primType )
• glEnd()
• primType determines how vertices are combined

GLfloat red, green, blue Glfloat
coords3 glBegin( primType ) for ( i 0 i lt
nVerts i ) glColor3f( red, green, blue
) glVertex3fv( coords ) glEnd()
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Display Window
(from Donald Hearn and Pauline Baker)
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Sample Programs

• include ltGL/glut.hgt // (or others,
  depending on the system in use)
• void init (void)
• glClearColor (1.0, 1.0, 1.0, 0.0) // Set
  display-window color to white.
• glMatrixMode (GL_PROJECTION) // Set
  projection parameters.
• gluOrtho2D (0.0, 200.0, 0.0, 150.0)

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Sample Programs

• void lineSegment (void)
• glClear (GL_COLOR_BUFFER_BIT) // Clear
  display window.
• glColor3f (0.0, 0.0, 1.0) // Set line
  segment color to red.
• glBegin (GL_LINES)
• glVertex2i (180, 15) // Specify
  line-segment geometry.
• glVertex2i (10, 145)
• glEnd ( )
• glFlush ( ) // Process all OpenGL
  routines as quickly as possible.

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Sample Programs

• void main (int argc, char argv)
• glutInit (argc, argv)
  // Initialize GLUT.
• glutInitDisplayMode (GLUT_SINGLE GLUT_RGB)
  // Set display mode.
• glutInitWindowPosition (50, 100) // Set
  top-left display-window position.
• glutInitWindowSize (400, 300) // Set
  display-window width and height.
• glutCreateWindow ("An Example OpenGL
  Program") // Create display window.
• init ( ) //
  Execute initialization procedure.
• glutDisplayFunc (lineSegment) // Send
  graphics to display window.
• glutMainLoop ( ) //
  Display everything and wait.

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Output