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Chapter 1 Graphics Systems and Models CSCI 346 Agenda Homework that is due Wednesday? Chapter 1 Chapter 1 Computer Graphics producing pictures or images using a computer 40 years ago drawing lines on a cathode ray tube Today produce images indistinguishable from photos

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chapter 1 graphics systems and models
Chapter 1

Graphics Systems and Models

CSCI 346

Homework that is due Wednesday?

Chapter 1

chapter 1
Chapter 1

Computer Graphics

producing pictures or images using a computer

40 years ago

drawing lines on a cathode ray tube


produce images indistinguishable from photos

produce “realistic” and animated dinosaurs

produce 3D worlds

computer graphics applications
Computer Graphics Applications

Display of Information



User Interfaces

display of information
Display of Information



Spatial Resource Planning (SRP)


MRI and

“seeing the unseen”

Visual Human Project




geographic information system gis
Geographic Information System (GIS)

Stores information about the world as a collection of thematic layers that can be linked together by geography.

Uses include

tracking delivery vehicles,

planning applications

modeling global atmospheric circulation.

spatial resource planning
Spatial Resource Planning

Spatially-referenced data within engineering, operations and distribution network management

Analogous to what Enterprise Resource Planning (ERP) solutions do for data held in accounting, human resources, procurement and project management systems,

magnetic resonance imaging mri and fmri
Magnetic Resonance Imaging (MRI) and fMRI

Uses magnetism and radio waves to produce images

ultrasound or ct scan
Ultrasound or CT Scan

Images are produced by very high frequency sound waves or x-rays

scientific visualization visual human project
Scientific VisualizationVisual Human Project

“Visible Man Thighs”

from GE Research and Development (Bill Lorenson)

scientific visualization electrophysiology
Scientific VisualizationElectrophysiology

Computed Potential Distribution on the Cardiac Surface during reentry: Spiral Tip Meandering, an arrhythmia model


"the evaluation of alternative solutions and the specification of a solution”

CAD / CAM (inc rapid prototyping)

VLSI design

generate a possible design, test, use solution as a basis for other solution


Simulators – surgery, flight


Educational (edutainment) software

Virtual Reality

user interfaces
User Interfaces

Interaction with computers




Pointing device

graphics system
Graphics System



Frame buffer

Output devices

Input devices


Simple system -- one processor handling

Normal processing

Graphics processing


Scan conversion

pixels and the frame buffer
Pixels and the Frame Buffer

Picture or image is produced as a array (raster) of picture elements (pixels)

Pixels are stored in part of memory called the frame buffer

frame buffer
Frame Buffer

depth -- number of bits used for each pixel

full color systems

true color systems

RGB color systems

24 or more bits per pixel

resolution -- number of pixels in the frame buffer

output devices
Output Devices

Dominant type of display is the CRT (cathode ray tube)

CRT emits light for a short time -- a few milliseconds.

For a human to see a steady image the path must be retraced or refreshed at least 50x/sechow are pixels displayed

how are pixels displayed
How Are Pixels Displayed?


displayed row by row


Displayed every other row

50-75X/second (50-75Hertz)

60Hz display refreshes the entire screen 30x/sec

Commercial TV

color crts
Color CRTs

3 phosphors

arranged in (sometimes triangular) triads

shadow mask CRT

screen with small holes ensures only one phosphor is excited

other output devices raster
Other Output Devices - Raster

Liquid Crystal Displays (LCD)

Plasma Displays

LED Displays


input devices
Input Devices





Data tablet

ways to read an input device
Ways to Read an Input Device


What is its input right now ?


Wait until the user does something

3d input devices
3D Input Devices

3D Input devices

Read a 3D position

Returns 3 numbers to the program: an (x,y,z) triple

Examples: digitizer, spaceball, glove

objects and viewers 3d world
Objects and Viewers3d world

Object is a constant

Viewer forms the image

human viewing system - back of eye

camera - film plane

different viewers see the same object differently

light and images
Light and Images

no light -- can't see anything

simplest scenario one light source

light from the source strikes various surfaces of the objects

portion is reflected and goes thru the lens to the camera

many variations based on the surface characteristics of the object


a form of electromagnetic radiation

the light or visible spectrum is a subset of the electromagnetic spectrum (includes radio waves)

light travels in straight lines from the source to the object

a theoretical point source would have monochromatic light emanating equally in all directions

ray tracing
Ray Tracing

simple concept

computationally expensive




and a light source

a ray: semi infinite line emanates from the point source and travels to infinity in some direction

ray tracing33
Ray Tracing
  • Tracing rays from the light source to the eye.
  • Lots of rays are wasted because they never reach the eye.
ray tracing34
Ray Tracing
  • Trace a new ray toward the light source.
ray tracing37
Ray Tracing

rays travel

directly to the viewer

out to infinity

strike an object and

mirror - reflect

diffuse surface - scatter

transparent - light passes thru the object but is changed maybe refracted or bent

ray tracing38
Ray Tracing

modeled on the real world

not fast -- in fact so slow that for real time or even semi real time graphics we need to look for another option

homework for this week
Homework for this week

Reading Chapter 2

Homework 1 - Due 9:00 AM 01/24/07