grafica(1): introduction dott. alessio malizia [email protected]
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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