computer graphics

Introduction to Computer Graphics

Pradondet Nilagupta
Dept. of Computer Engineering
Kasetsart University

204481 Foundation of Computer Graphics March 7, 2013 1

Lecture Outline

 Course Information: Format, Resources
 Overview
 Topics covered
 What is computer graphics?
 Applications

204481 Foundation of
Computer Graphics March 7, 2013 2

Course Info and Administrative

 Instructor: Pradondet Nilagupta
 E-mail: pom@ku.ac.th
 Phone: 9428555 ext. 1415 (office)
 Office hours: after class; 1-2pm Monday or by
appointment
 Web Page
 Course Homepage:
http://www.cpe.ku.ac.th/~pom/courses/204481/
204481.html
 Course Syllabus:
http://www.cpe.ku.ac.th/~pom/courses/204481/syllabus.html

Course Overview (1/2)

 Graphics Systems and
Techniques
 2-D, 3-D models: surfaces,
visible surface identification,
illumination
 Photorealistic rendering :
shading models, ray tracing,
radiosity
 Operations
 Surface modeling, mapping
 Pipelines for display,
transformation, illumination

Course Overview (2/2)

 Mathematical Review
 Review of mathematical foundations of CG:
analytic geometry, linear algebra
 Line and polygon rendering
 Matrix transformations


Relevant Disciplines
Rendering Hardware CAD
Immersive Training
VR Systems CAE / CASE
 Analytic Geometry Portable/Embedded CG CAM
Tutoring Interfaces

 Art and Graphic Design
 Cognitive Science Color/Optical Models
CG/Vision Duality
 Computer Engineering Interface Design

 Engineering Design Layout
CG Design
 Education Visualization
 Film
Parametric Equations
 Human Factors Conics Computer
Polygon Rendering
 Linear Algebra Graphics
 Numerical Analysis (CG)
Surface Modeling
Physically-Based Modeling
Stat/Info Visualization

Transformations
Change of Coordinate Systems
User Modeling Animation
204481 Foundation of Ergonomic Interfaces, I/O Large-Scale CG


What is Computer Graphics?

204481 Foundation of Computer Graphics March 7, 2013 7

This is not Computer Graphics
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 [ 29:akin@sgi.com ] Re: Future development of
PEX/PHIGS]
 [ 9:bthompso@reed] What is a good book for
Digital Image Processing]
 [ 15:csp48@seq1.ke] Help! ASCII picture
needed…
 [ 14:rcj2@cbnewsd.] Re: 3D igitizers… again
 [240:raj@ms.uky.ed] Call For Papers -- ACM
Multimedia '93

What is Computer Graphics ?

 Computer graphics is commonly
understood to mean the creation, st
orage and manipulation of models a
nd images. (Andries van Dam)
 Computer graphic is concerned with
 all aspects of producing pictures or
images using a computer.
 the pictorial synthesis or real or
imaginary objects from their computer
based model

Computer Graphics

 Computer Graphics
 Synthesis of graphical images
 Visualization :

creating an image from an abstract, symbolic
description.
 Generation of Synthesis Image
 using graphical primitives
 data from real world phenomena


Image Processing

 Image Processing
 the transformation of an existing image into a
more desirable or useful image.
 image enhancement, pattern detection

The following images represent how noise affects images

Image Analysis

 Image Analysis (Computer Vision)
 extracting symbolic information from the
image.

Computer Graphics Data => Picture
Image Processing Picture => Picture
204481Image Analysis of
Foundation Picture => Data

What is Interactive Computer Graphics?

 User controls contents, structure, and
appearance of objects and their displayed images
via rapid visual feedback
 Basic components of an interactive graphics
system
 input (e.g., mouse, tablet and stylus, force feedback
device,scanner…)
 processing (and storage)
 display/output (e.g., screen, paper-based printer, video
recorder…)

Why Computer Graphics? (1/5)

 Humans communicate well with images
 1/3 of your brain is devoted to visual
processing
 A picture is worth a few hundred
megabytes



 Developing Computational Capability
 Rendering: synthesizing realistic-looking,
useful, or interesting images
 Animation: creating visual impression of motion
 Image processing: analyzing, transforming,
displaying images efficiently



 Better Understanding of Data, Objects,
Processes through Visualization
 Visual summarization, description,
manipulation
 Virtual environments (VR), visual monitoring,
interactivity
 Human-computer intelligent interaction (HCII):
training, tutoring, analysis, control systems


 Time is Right
 Recent progress in algorithms and theory
 Rapidly emergence of new I/O (display and data
acquisition) technologies
 Available computational power, improving price-
performance-ratio of hardware
 Growth and interest of graphics industries (e.g.,
information visualization, entertainment CAD)



 advances in the last decade due mostly to the
microchip
 software advances, especially in object-oriented
programming and real-time rendering algorithms
 Hardware advances continue to benefit graphics:
 faster inexpensive microprocessors and dedicated
graphics chips
 screen technology: High-definition television (HDTV),
colour LCD
 virtual reality interfaces (corneal implants?)

Image Synthesis Pipeline
Graphics
Database
Editing

Front-End

Graphics
Database
(Geometry Processing)

Back-End

Display
Traversal
Modeling
Transformation
Viewing
Operation
 (Rasterization)

• Visible-Surface
Determination
• Scan Conversion Image
• Shading /
Illumination


A Brief History

 teletype printouts were first graphical output devices
lightpens were an early input device CAD applications beg
an in the 1960's plotters also a 60's development: high-res
olution, but slow main bottlenecks of computer graphics ba
ck then
 cost of graphics hardware
 expense of computer resources
batch systems weren't suitable
for interactive graphics
non-portability of hardware and
software
a new field: technology was


204481 primitive
Foundation of

History of Computer Graphics (1/5)
 1950 MIT’s Whirlwind
computer had computer
generated CRTs mid 19
50s SAGE command an
d control
 1960s Ivan Sutherland’s
thesis - Sketchpad
 introduced data
structures and interactive
techniques
http://www.computer.org/history/development/1951.htm


 1960s GM (general Motor)
 developed CAD (Computer Aided Design) and
CAM
 1968 Tektronix storage tubes
 1970s Boeing CAD CAM


 Mid 1970s engineering workstations and
personal computers emerged separately
 1980s new algorithms and techniques
 new standards
 ever more powerful system
 transition from specialized field
 1990s widespread use
low cost, but powerful personal workstations


 networks

 essential part of systems

 now part of multimedia


At first - progress was slow because
 cost of equipment was high (specially

memory)
 significant computing resources needed

 difficulty in writing software ( harder than it

looks)
 lack of standard and thus portability

 lack of software tools



Now - previous use
 cost of equipment is low.

 Most computer have necessary

computing resources for graphics
 established standards,

implementations and tools
 still difficulty in writing software ( still

harder than it looks)

Some of Historical Picture (1/2)
 First truly interactive graphics
system, Sketchpad, pioneered
at MIT by Ivan Sutherland for h
is 1963 Ph.D. thesis. Sketchpad
, A Man-Machine Graphical Comm
unication System:
 Sketchpad in 1963. Note the
use of a CRT monitor, light pe
n and function-key panel.


Some of Historical Picture (2/2)

http://www.man.ac.uk/Science_Engineering/CHSTM/nahc.htm
John VonNeuman

http://ei.cs.vt.edu/~history/VonNeumann.html Mark I

Applications of Computer Graphics

Applications of Computer Graphics
 divided in 4 majors area

 Display of Information
 Design

 Simulation

 User Interface


Display of Information

 Geographic
information system
(GIS)
 Computerized
Tomography (CT)
 Magnetic resonance http://www.soest.hawaii.edu/soest/about.ftp.html

imaging (MRI)
 Ultrasound
 positron-emission
tomography (PET)
204481 Foundation of http://www.queens.org/qmc/services/imaging/ct.htm


Design

 Computer-Aided Design (CAD)
 Architecture
 Design of Mechanical part

 VLSI

 etc...

http://www.memagazine.org/contents/current/features/push/push.html

Simulation

 Graphical flight simulator
 reduce training process
 Robotic simulation
The Concorde Panel.
 TV, Movie, advertising industries
 generate photo realistic images
 Virtual Reality (VR)
 reduce risk of training
 surgery
 astronaut
204481 Foundation of http://www.motionshop.com/pr/festocosimirlg.shtml


User Interfaces

 Window system
 Window 2003
 X window

 MAC OS

 Graphical Network browsers
 Netscape
 Internet Explorer


Areas of research in Graphics (1/2)

 mathematical modeling:
 interpolation, curve and surface fitting
 computational geometry: algorithmic
applications in geometry
 study of light and optical phenomenon: colour,
texture, shades
 modelling the characteristics of physical
objects (bouncing Jello)


Areas of research in Graphics (2/2)

 Software technology
 standardized graphics languages and libraries
 graphics tools and interfaces
 algorithm design
 Hardware
 specialized graphics chips, monitors, interface
devices


Graphics Applications

 Entertainment: Cinema
Pixar: Geri’s Game

Universal: Jurassic Park

Antz

A bug’s Life

Graphics Applications (1/4)

 Entertainment: Games

Aki Ross : Final Fantasy

Star Wars Jedi Outcast: Jedi Knight II

Quake III


 Medical Visualization

The Visible Human Project
http://www.ercim.org/publication/Ercim_News/enw44/koenig.html


 Computer Aided Design (CAD)



 Scientific Visualization


Hypermedia User Interfaces (1/2)
NCSA D2K:
http://chili.ncsa.uiuc.edu
Visual programming system for
high-performance knowledge
discovery in databases (KDD)

 Hypermedia
 Database format (similar to hypertext) that provides display-based
access to (internetworked) multimedia (text, image, audio, video,
etc.) documents
 Chimera: http://www.ics.uci.edu/pub/chimera/

Hypermedia User Interfaces (2/2)

 Virtual Environments
 Immersion: interactive
training, tutoring systems
 Entertainment hypermedia
 Visualization and Computer-
Aided Design and Engineering
(CAD/CAE)
 Visualization: scientific,
data/information, statistics
 User interfaces for
CAD/CAE/CAM/CASE:
http://www.isii.com
http://www.psl.cs.columbia.edu/chime/

Curve and Surface Modeling
1 http://www.geocities.com/SiliconValley/Lakes/2057/nurbs.html
2
3
4

5

8 7

6


Photorealistic Illumination Models
http://www.pixar.com

http://www.ktx.com/3dsmaxr3/ http://www.aliaswavefront.com


Fractal Systems

http://sprott.physics.wisc.edu/fractals.htm


Information Visualization

Visible Decisions SeeIT (http://www.vdi.com)

Interesting Industrial Applications
6500 news stories
from the WWW
in 1997

Cartia ThemeScapes – http://www.cartia.com

Hypermedia and Statistical Visualization

Destroyed
Normal
Extinguished
Ignited
Fire Alarm
Engulfed
Flooding

Virtual Environments for
DC-ARM – http://www-kbs.ai.uiuc.edu Immersive Training

Overview of Programmer’s Model (1/2)
 Pixel - smallest addressable unit of display
 Hardware (I/O)
 output display device (normally raster scan)
 on the order of a million pixels displayed
 image stored in memory by pixel
(how much memory?)

video controller

scans the memory periodically (30-72 times a second)
produces video signal to drive a video monitor (or flat screen di
splay)

input devices - keyboard, mouse (track ball), tablet, voice etc.


Overview of Programmer’s Model (2/2)

Software
 application data

 application program

 graphics interface

 operating system


Graphical System And Standard
(1/5)

 Graphical Systems
 High level language interface to graphical
devices.
 Intended for development of portable code.
 Standard graphical systems include
CORE,


 Graphical Kernel System (GKS), GKS+


Programmers Hierarchical Interactive Graphics
System (PHIGS), PHIGS+

OpenGL, DirectX, Quickdraw 3D, VRML,
Open Inventor, X-Windows.

(2/5)

 Requirements of Graphical Systems
 Portability
 Device Independence
Concept of a logical device.
 Language Independence
Language Bindings for graphical systems.
 Computer Independence
Trade-off between standard hardware and high
performance hardware.
 Programmer Independence
 Flexibility - In conflict with portability.

(3/5)

 Graphical Kernel System (GKS)
 Workstation
 GKS has concept of a workstation.
 Device Normalisation
 World Coordinates, Window in World Coordinates
 Clipping to the window
 Normalised Device Coordinates [0,1]x[0,1]
 Normalisation Transformation
 Viewports in normalised device coordinates


(4/5)

 Output Functions

Line-Drawing Primitives
 Area-filling primitives
 Text Output
 Input Functions

Logical input types : Locator, Valuator, Choice,
String, Pick, Stroke.


(5/5)

 Input Modes

Request mode: waits for a request for an event.
 Sample mode: continually samples value of input
device.
 Event mode: unsolicited input stored on a stack,
made available for processing in FIFO order.
 Mixed mode.


Professional Societies

ACM SIGGRAPH
- Association for Computing
Machinery Special Interest G
roup in Graphics
IEEE
- The Institute of Electrical and
Electronics Engineers,
Technical Committee on Co
mputer Graphics

Software Portability and graphics
standards
STANDARD
ORGANIZATION
 ANSI = American National

Standard Institute (private,
non government)
 ISO = International

Standards
Organization(voluntary,
non treaty)
 ANSI is a member of ISO

History: graphics libraries

 initially, low-level device-dependent
packages were the norm
 movement towards high-level device-
independent packages, in order to promote
application program portability
 requires standardization:


Official Standards

 1977 and 1979 - 3D SIGGRAPH CORE (ACM
SIGGRAPH)
 3D Core Graphics System ("Core") dev'd in late
70's as unofficial std
 GKS (Graphical Kernel System, 1985): official 2D
standard built from Core
 GKS-3D (1988): 3d objects ANSI X3.124-1985
 PHIGS (Programmer's Hierarchical Interactive
Graphics System, 1988) 3D nested objects
 PHIGS+ (1988): rendering enhancements

Emerging Standards in APIs

 OpenGL (developed by Silicon Graphics)
 open standard
 available on all platforms
 intended for professional-level graphics like
CAD
 Direct3D
 developed by Microsoft
 Windows only
 intended for games

Some Notable Systems
 Tektronix commands in BASIC (mid-1970s)
 HP commands (Hewlett Packard)
 Microsoft BASIC (for PCs) graphics
commands (early 1980s)
 QuickDraw (Apple Macintosh)
 X (MIT)
 OpenGL (Silicon Graphics)
 SRGP (Simple Raster Graphics Package)
 SPHIGS (Simple PHIGS)
 MS Windows
 Java AWT

Good graphics requires ? (1/3)
 ability to control every dot (pixel) of display
 ability to control primitive shapes on the
screen
 models to deal with images as a whole
 use of color, lighting, and shading
 construction of "languages" or "packages"
to extend languages
 knowledge of hardware
 systems work

Good Graphics requires ? (2/3)

 mathematical transformations and
representations
 transmission of pictures and commands
to make pictures
 ability to store lots of information
 high performance computers
 algorithms such as visible surface
algorithms

Good Graphics requires ? (3/3)

 understanding and manipulation of
data structures
 good software engineering principles

 human factors engineering

 some feeling for artistic principles

 lots of effort - harder than it looks


Lecture Topics
 Introduction Visible Surface
 Mathematical Determination
Foundation  Algorithm efficiency
 Coordinate Systems  Z-buffer algorithm
 Introduction to  Scan line algorithms
Graphics in 2D
 Visible-surface Ray Tracing
 Windows and Clipping
 Introduction to
 Other algorithms
Graphics in 3D  Color Models
 Viewing in 3D  Illumination and Shading

Mathematical foundation

 Mathematical appears throughout 3D graphics
Example:
 Object surfaces can be represented as polygons
whose vertex position are specified by vectors
 Rendering requires testing whether vertices lie in
front of or behind various planes.
 The test involves a dot product with the plane’s
normal vector.


Geometric transformation

 Goal: specify object’s position and
orientations in a 3D world
 Use Linear transformations that rotate

and translate objects’ vertices.
 Apply these transformations in matrix

form


Viewing

 Goal: map the visible part of a 3D
world to a 2 D image
 Use camera-like parameters to define

a 3D view volume
 Project the view voulme onto a 2D

image plane
 Map viewport on the image plane to

the screen

OpenGL

 OpenGL is strictly defined as “a software
interface to graphics hardware”.
 It is a 3D graphics and modeling library
 variety purposes, CAD engineering,
architectural applications, computer-genera
ted dianosaurs in blockbuster movies
 Developed by SGI


Clipping

 Goal: cut off the part of objects outside
the view volume to avoid rendering
them


Scan Conversion

 Goal: convert a project, clipped object
into pixels on raster lines.
 Use efficient incremental methods


Antialiasing

 Raster displays produce blocky
aliasing artifacts
 Antialiasing techniques reduces the

problem by applying the theory of sam
pling and signal processing


Color

 Various color spaces provide ways to
specify colors in term of components:
 red, green, blue

 hue, saturation, value

 Different output devices display

different subsets of the perceptible col
ors

Hidden Surface Removal

 When several overlapping polygons are
drawn on the screen, which one is on
top?
Which is
right?


Z-buffering

 A fast hardware solution is This pixel is
drawn on
the Z-buffer
screen
 The “depth” of each pixel
relative to the screen is Screen
calculated and saved in a Polygons
buffer
 The pixel with the smallest
depth is the one that is
displayed
 The other pixels are on Z
surfaces that are hidden

Lighting Models and Shading

 For visual realism, lighting Ambient lighting:
models have been developed
to illuminate the surfaces of
solid models
 These models incorporate
incident reflected light
 ambient lighting and illumination light
 diffuse reflection of directional
lighting
 specular reflection of directional reflected light
incident
lighting light


Ray Tracing
Light Source

Shadow Ray
Eye
Object
Eye Ray

Shadow Ray
Object
Light Source
 Ray tracing traces a ray
of light from the eye to a
light source
 Ray tracing realistically

renders scenes with
shiny and transparent
204481 objects
Foundation of

Radiosity

 Diffuse illumination
results from the
absorption and reflection
of diffuse light from
many objects in the
scene
 Radiosity uses thermal
models of emission and
reflection of radiation to Radiosity is very good at
accurately calculate rendering architectural
interiors
diffuse lighting

Texture Mapping

 For realism, photographic textures are
“mapped” onto the surfaces of objects
 Example textures: texture
mapping
 woodgrain
 concrete
 grass reflections

 marble shadows

 Texture mapping is very computationally
intensive

Example of Shading

Wireframe Flat Shaded

Smooth Shaded Shadows

computer graphics

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