Introduction to computer graphics

Introduction To Computer Graphics
Prepared By:Er. Loknath Regmi
Computer Graphics

Course Overview
 Introduction, History
 Application in different fields like CAD, schematic capture, medicine, art etc.
 Hardware concepts
 2-D and 3-D algorithms
 Line drawing, viewing transformations, other transforms (scaling, rotation,
translation)
 Curve Modeling
 Mathematics of generation of parametric cureve like Bazier, Spline, Hermite
 3D Object Modeling
 Visible Surface Detection and Surface Rendering
 Introduction to Animation
 Text Book
 Computer Graphics CVersion – Hearn & Baker

Computer Graphics
A sub-field of computer science which studies method for
digitally synthesizing and manipulating visual content.
Are texts and sounds graphics ???
No (wikipedia); but text??
Generally refers to (Ref:Wikipedia):
Representation and manipulation of pictorial data by computer
Various technologies used to create and manipulate such pictorial data
The image so produced

Image Processing Vs
Computer Graphic
 Computer Graphics
 a mathematical modeling
deals about synthesis, manipulation, processing, and
storage of image of an object
 a complete package on generation and modeling of
graph
 deals about generation of math mathical model
 Image Processing
 not explain about synthesis of image
 explain manipulation and processing of existing image
 use the mathematical model for processing of imagePrepared By:Er. Loknath Regmi

History of Computer Graphics
 Late 1950’s –Whirlwind computer (MIT) and SAGE (Semi Automatic Ground Environment);
an automated control system to bombard enemy
 Used CRT and light pen for user interactive environment
 1959 –TX-2 (MIT’s Lincoln Laboratory); first interactive interface computer system using
light pen and bank switches
 1960 –William Fetter
 Introduced phrase “Computer Graphics”
 Boeing man (Fetter called it First Man) for human figure simulation to describe different user
environment
 Mid 1960’s – MIT activities in computer graphics field promoted early computer graphics
industries likeTRW, General Electric, IBM
 End 1960’s – organization, conferences, graphics standards and publications
 1969 – ACM initiated Special Interest Group In Graphics (SIGGRAPH)

History of Computer Graphics
1970’s – powerful PCs to draw basic and complex shapes
1980’s – artists and graphics designers preferred to use
Macintosh and PCs
Late 1980’s – 3-D computer graphics with SGI (Silicon
Graphics) computers
1990’s onwards – 3D graphics in gaming, multi media and
animation, GUI

Applications Areas of CG
Display of Information
Design
Simulation
Computer Art
Entertainment

Display of Information
 Graphics for Scientific, Engineering, and Medical Data
Nebla Medical Image

Design
Graphics for Engineering and Architectural System
Design of Building,Automobile,Aircraft, Machine etc.
AutoCAD
2002
Interior Design

Simulation
 Computer-Generated Models of Physical, Financial and
Economic Systems for Educational Aids
Flight Simulator Mars Rover Simulator

Computer Art
 Graphics for Artist
Metacreation Painter

Entertainment
 Graphics for Movie, Game,VR etc.
Final Fantasy
Online Game

What’s Our Scope?
Not aTutorial on Commercial Software
3DMax, Maya, Photoshop, etc.
Not about Graphics Business
3D online-game, E-commerce, etc.
Graphics = Algorithm forVisual Simulation
Imaging, Modeling, Rendering,Animation

Pixels
The computer stores and displays pixels, or picture elements.
A pixel is the smallest addressable part of the computer screen.
A pixel is stored as a binary code representing a colour.
The code for a pixel can have between 1 and 32 bits of binary
code.
Here is the Photoshop logo at normal size.
 Here it is enlarged 400% so that you can see the individual pixels.

Pixel Depth
Pixel Depth describes the number of bits used to store each pixel.
The greater the pixel depth, the more colours a pixel can have.
Colour graphics vary in realism depending on resolution and pixel
depth.
The greater the pixel depth, the bigger the file.

Examples of Pixel Depth
Monochrome
Monochrome graphics have one-bit pixel depth. (pure black or pure
white)

Gray-Scale
Gray-Scale graphics have more bit-depth
(No colours besides black, white and grey)

8 Bit Colour
 8 bits per pixel provides 256 colour
choices
(Typical of the web - that’s why web graphics need some
skilful preparation)

 24 or 32 bits per pixel provides thousands or millions of
colour choices. (Typical of graphics and games software)

Resolution
Resolution refers to the density of dots on the screen or
printed image and directly affects quality
The higher the resolution, the less jagged the image.
Resolution is measured in DPI (Dots per Inch)
(The printing industry is largely unmetricated and still
uses inches because printing measures such as the Point
(1 72nd of an inch) do not easily convert to metric
units.)
The higher the resolution, the better the potential
output.

Typical Resolutions
Screens generally operate at around 72-100 dpi
Printed images range from 300 to 2400 dpi
Resolution affects the file size of an image.
The higher the resolution, the bigger the file.
The visible resolution is limited to the maximum
possible on the output device (screen or printer).
No matter how high the resolution of a photograph, it
will show at the resolution of your screen or printer.

File Types
 There are many kinds of graphics file formats and this is
a specialised area and a bit complicated.
Examples : bmp GIF JPEGTIFF PICT Raw
For most applications involving photographic images,
use the JPEG file format (Joint Photographic Experts
Group)
For graphics or paint type files use GIFs
(Graphical Interchange Format)

JPEG
The JPEG format can be used by most applications and
all browsers
It has very good compression algorithms
It stores a good quality image in a remarkably small file
with little or no loss of quality
JPEG offers 10 quality levels with correspondingly
smaller files and greater losses in quality

GIF
You should choose a GIF format instead of JPEG when
You have a graphic with only a few colours such as a logo or
icon
You want to create an image with some transparent parts for a
web page
You want the smallest possible file size with totally lossless
compression
You want to combine a few images together into an animation
You want to save text as a graphic

Introduction to computer graphics

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