1. Introduction and history

Brock University
COSC 3P98 Computer Graphics
Instructor: Brian J. Ross

Introduction to COSC 3P98 Computer Graphics

Course purpose: an overview of computer graphics technology
(see course outline)
Course involves

fundamentals: technological methods and principles
practical: programming assignments
theory: some mathematics and algorithms

Assignments:
- programming in C and OpenGL
- C++: if you want
Resources:
- Reserve reading in library
- Online documentation: OpenGL
- Course WWW page: lectures, communication, misc utilities and items of interest
- online OpenGL Red Book (but it's out of date)
- the web: lots of information! (but: Do Your Own Work!)

Graphics

computer graphics: the use of visual representation for modeling data and conveying information
a topic of study since the 60's
active area of computer science research
recent advances are changing the way computer technology effects us:
- Graphical user interfaces
- on-line information databases
- computer-aided design (CAD)
- entertainment industry: commercials, movies, games
- virtual reality

Why use graphics?

"a picture is worth a 1000 words"
humans are naturally skilled at interpreting visual information
- eg. it is easier to understand a bar chart, than a table of numbers
graphics therefore creates a human-oriented medium with which the computer and human can interact
- permits the synthesis of objects: their visualisation, modeling
motion dynamics: the movement of an object or a viewer within an environment
- inspect automobile design in CAD system
- non-intrusive medicine
- flight simulator
update dynamics: changes in the object being viewed
- eg. stresses on bridges
- systems incorporate physics simulations : gravity, forces, fluid dynamics
Note that early CAD systems were important for graphics becoming an active research and industrial area.

Some terms

interactive computer graphics: that in which real-time performance and human interaction is of concern
pixel: one visible point on the computer screen
bitmap: data structure in which bit(s) maps to a pixel
image processing: manipulating images in order to highligh various aspects of interest; used by computer vision
- computer graphics constructs images from models
- computer vision constructs models from images
- both areas share technology, ie. image manipulation techniques
photorealism: generate graphic images equal to, or surpassing, realism of photographs
non-photorealism (NPR): when realism is not a goal
- anime cartoon effects
- van Gogh style images
- Example
CRT: cathode-ray tube (TV tube)

Graphics and Hardware Advances

advances in the last decade due mostly to the microchip
what was once esoteric and computationally expensive, can now be done on a cell phone
faster inexpensive (parallel) microprocessors and dedicated graphics chips
developments in photorealism have benefitted from hardware devts.
graphics cards support highly parallel dedicated graphics processing.
- Often used for non-graphics processing (number crunching)
screen technology: High-definition television (HDTV), colour LCD, OLED
virtual reality interfaces (corneal implants?)
3D scanners: find surface geometries of objects
- NextEngine
3D printers: make 3D object from computer models
- Zcorporation
- Makerbot: and example video

Graphics and Software Advances

Hardware advances depend upon software to run it.
Lots of areas of graphic software advances:
- realistic rendering techniques: radiosity
- real-time rendering algorithms
- GUI design
- object-orientation: for supporting complex systems
immersive environments, virtual reality

Areas of research in Graphics

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

Types of applications

dimension of object: 2D or 3D
type of interaction:
- batch: photorealism, animation (although often becoming realtime), plotters
- realtime, interactive
Role of the picture
- picture is the purpose: drafting, painting, artwork, desktop publishing
- picture is a tool: CAD, user interfaces
Degree of realism
- 16 or 16 million colours
- draft or photorealistic effects (or NPR)

A Brief History

teletype printouts were first graphical output devices
lightpens were an early input device
CAD applications began in the 1960's
plotters also a 60's development: high-resolution, but slow
main bottlenecks of computer graphics back 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 primitive

History

Things changed with advent of microchip:
- desktop mini- and microcomputers made graphics hardware commercially viable
Output technology (display and printer devices)
- hard copy: from monochrome teletype and plotters, to colour inkjet and laser printers
- some graphics terminals had builtin thermal printers
Input technology:
- keyboards, digital tablets, touch sensitive screens, optical and mechanical mice, trackballs, voice,...
- 3D scanners, 3D mice, VRML helmets, motion capture suits, ...

Vector displays

early display device
vector: line defined by a start and end point on screen
a refresh buffer contains digital commands telling what to draw (location of vectors, draw and move commands, ...)
vector generator: converts commands in refresh buffer into analog signals that are displayed on a phosphor (green) screen
random scan: vectors drawn in the order they reside in buffer
refresh cycles had to occur at 30 Hz: greatly limited complexity of picture
newer tubes had lower refresh rates
dedicated minicomputers later used to handle graphics handling

Example image (Atari Battlezone):

Raster displays

based on television technology
screen is divided into pixels at some resolution (fineness)
refresh buffer contains digital information that is converted directly into screen pixels by hardware
raster: set of raster lines or rows of pixels
when you change some bits in the raster, the screen is changed
television technology has improved resolution
the bigger and finer the picture, the larger the memory req'd for the refresh buffer. But memory is now cheap!

Raster refresh

Comparing Raster and Vector

advantages of vector:
- higher resolution, especially for diagonal lines
- geometry objects (lines) whereas raster only handles pixels
- eg. 1000 line plot: vector disply computes 2000 endpoints
- raster display computes all pixels on each line
advantages of raster:
- cheaper
- colours, textures, realism
- unlimited complexity of picture: whatever you put in refresh buffer, whereas vector complexity limited by refresh rate

Flat-panel displays

2 types: emissive (plasma) and non-emissive (LCD)
Plasma:
- panel of gas (neon) and grid of horizontal and vertical conductors
- precise firing a charge at intersection of grid causes gas to glow
- RGB filters then produce colour in a way similar to CRT's
- advantage: high resolution, getting better, lower energy
- disadvantage: limited lifespan (like CRT's)
LCD:
- polarized light is shone through liquid crystal mesh
- turning on/off mesh locations will either allow or block light
- passive: need external lighting to see result
- can use backlighting, RGB mesh for colour
- active LCD: a transistor at each pixel for activating LCD
- advantages: hi rez, low power, very long life
- disadvantages: more expensive for large displays, some latency (liquid movement time) means animation can be blurry, dimmer than plasma

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:
- 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
- PHIGS (Programmer's Hierarchical Interactive Graphics System, 1988) 3d nested objects
- PHIGS+ (1988): rendering enhancements
- GL: SGI, from early 90's
- OpenGL: new standard, open version of GL
- Renderman: Pixar rendering language
- Direct-3D: Microsoft Windows 3D standard
- CG, OpenGL 2.0: vertex and pixel shaders

Preview

Application model: mathematical model of objects to be displayed
- eg. data structure containing the coordinates of a polygon
Application program: program that defines application model, defines what user does with it, process user input, etc
Graphics system: software and hardware component that takes application model, and using directions from application program, transforms them into a visual object on screen (printer, plotter, ...)

Preview

the types of transformations the graphics system performs on model is primary focus of this course
the models are mathematical: lots of trig, matrix multiplication, calculus (when you get into splines)
graphics is a good example of applied mathematics: abstract mathematical representations of physical objects are mathematically transformed into pseudo-realistic representations on the screen
graphics naturally falls into conceptual categories of 2D (drawing on the plane) and 3D (drawing in 3D space), and the transition area between them
usually math is "intensive" when techniques or algorithms are being derived
- once the formula and algorithm is derived, they're implemented into graphics libraries
- implementation is often hardware-supported

Back to COSC 3P98 index

COSC 3P98 Computer Graphics
Brock University
Dept of Computer Science
Copyright © 2009 Brian J. Ross (Except noted figures).
http://www.cosc.brocku.ca/Offerings/3P98/course/lectures/intro/
Last updated: August 24, 2009