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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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CSCI 346

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Chapter 1 graphics systems and models l.jpg

Chapter 1

Graphics Systems and Models

CSCI 346


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Agenda

Homework that is due Wednesday?

Chapter 1


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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

produce “realistic” and animated dinosaurs

produce 3D worlds


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Computer Graphics Applications

Display of Information

Design

Simulation

User Interfaces


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Display of Information

Maps

GIS

Spatial Resource Planning (SRP)

http://earth.google.com/

Medicine

MRI and http://mednews.stanford.edu/stanmed/2005fall/story_images/brain-fmri.jpg

“seeing the unseen”

Visual Human Project

biology

electrophysiology

mathmatics


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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.


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GIS


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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,


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Magnetic Resonance Imaging (MRI) and fMRI

Uses magnetism and radio waves to produce images


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Ultrasound or CT Scan

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


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Scientific VisualizationVisual Human Project

“Visible Man Thighs”

from GE Research and Development (Bill Lorenson)


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Scientific VisualizationElectrophysiology

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


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Design

"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


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Simulation

Simulators – surgeryhttp://www-kismet.iai.fzk.de/VRTRAIN/phD_main.html, flight

Games

Educational (edutainment) software

Virtual Reality


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User Interfaces

Interaction with computers

Windows

Icons

Menus

Pointing device


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Graphics System

Processor

Memory

Frame buffer

Output devices

Input devices


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Processor

Simple system -- one processor handling

Normal processing

Graphics processing

Rasterization

Scan conversion


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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


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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


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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


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How Are Pixels Displayed?

Noninterlaced

displayed row by row

Interlaced

Displayed every other row

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

60Hz display refreshes the entire screen 30x/sec

Commercial TV


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Color CRTs

3 phosphors

arranged in (sometimes triangular) triads

shadow mask CRT

screen with small holes ensures only one phosphor is excited


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Other Output Devices - Raster

Liquid Crystal Displays (LCD)

Plasma Displays

LED Displays

Printers


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Input Devices

Keyboard

Mouse

Lightpen

Joystick

Data tablet


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Ways to Read an Input Device

Sampling

What is its input right now ?

Event-based

Wait until the user does something


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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


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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


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Objects and ViewersPinhole Camera


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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


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Light

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


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Ray Tracing

simple concept

computationally expensive

scene

viewer

objects

and a light source

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


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Ray Tracing


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Ray Tracing

  • Tracing rays from the light source to the eye.

  • Lots of rays are wasted because they never reach the eye.


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Ray Tracing

  • Trace a new ray toward the light source.


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Ray Tracing


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Ray Tracing - Recursive


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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


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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


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Homework for this week

Reading Chapter 2

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


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