grafica(1): introduction dott. alessio malizia malizia@dsi.uniroma1.it

Grafica (1): Introduction

Dott. Alessio Malizia

Malizia@dsi.uniroma1.it

History

• 1980s CG small specialized field• First built-in raster graphics displays

– Xerox Star

– Apple Macintosh

– IBM PC

• Bitmap graphics– Rectangular representation of 0s and 1s array of points

(pixels)

– Less expensive and easy to use

WIMP

Image Processing vs Computer Graphics

• Analysis– Picture processing– Image enhancements– Pattern Detection and Recognition– Scene Analysis and Computer Vision

• Synthesis– Pictorial representation of real or imaginary

objects from their computer-based models

Image Processing

Computer Graphics

Advantages of Interactive Graphics (1)

• Natural communication for humans, since our pattern recognition abilities we perceive and process graphics rapidly

• Ancient Chinese “a picture is worth ten thousand words”

• Static pictures are good but dinamic are evn better for communication “a moving picture is worth ten thousand static ones”

Advantages of Interactive Graphics (2)

• Motion dynamics– Object can be moved with respect to a stationary

observer• Flight simulator• Arcade games

• Update dynamics– Actual change of shape, color or other props of the

object beng viewed• Display deformations of an aircraft plane structure in flight• A graphical manipulation by the user change the system

reaction

Motion dynamics

Update dynamics

CG uses

• User Interfaces (WIMP)• Intercative plotting in business, science and tech.• Office automation and electronic publishing• Computer aided drafting and design• Simulation and animation for scientific

visualization and entertainment• Art and commerce (advertising)• Process Control (flow)• Cartography (natural phenomenon)

Classification of applications (1)

• By type (dimensionality) of presented objects and kind of picture to be produced

Type of obj Pictorial representation

2D Line drawing

Gray scale image

Color image

3D Line drawing (wireframe)

Line drawing with effects

Shaded color images

Wireframe and Shaded

Classification of applications (2)

• By type of interaction – Offline plotting (predefined physical data)– Interactive plotting (user supply parameters)– Calculating the object and fly around it (real

time under user control or scientific viz)– Interactive designing (start with blank screen

and user create views)

Classification of applications (3)

• By the role of the picture– If the picture is an end or part of a process– Example in cartography: drafting, raster

painting, animation and artwork till the end drawing.

Classification of applications (4)

• By logical and temporal relationships between objects and their pictures– Only one picture at a time (plotting)– Time-varying sequence of raleted pictures

(motion or update dynamics)– Structured collection of objects and their parts

(CAD, CAM)

Development of CG

• Whirlwind Computer 1950s MIT– Computer driven CRT displays for output

CG limitations

• High cost of the graphics hardware

• Need for large scale, expensive computing resource for interactivity

• Difficulty of writing large interactive programs (assembler)

• Non-portable software

Output Techs: vector display

Output techs: raster display

Raster Scan

Vector scan VS Raster scan