Foundations of Computer Graphics — Unit 1
Introduction to Computer Graphics
1. Introduction to Graphics Systems
Computer Graphics refers to the creation, manipulation, and representation of visual
images using computers. It enables us to generate pictures, animations, and visual
simulations that help in understanding data or presenting information clearly. Computer
graphics form the backbone of applications such as gaming, animation, simulations,
CAD/CAM, GUI design, and virtual reality.
Example: When you play a video game, every moving object, shadow, and explosion is
rendered through real-time computer graphics.
2. Basic Elements of Computer Graphics
The basic elements include: points, lines, curves, polygons, and color. These primitives
are combined to create more complex images.
Point: Smallest addressable element in a display; represented by pixel
coordinates (x, y).
Line: Formed by connecting two points; used to construct shapes.
•
Polygon: Closed shape made up of lines; e.g., triangle, square.
•
Color: Each pixel carries color information in RGB (Red, Green, Blue) or other
•
models.
Figure Description: Imagine a coordinate grid where each pixel is a tiny dot; connecting
dots forms lines and shapes.
•
3. Applications of Computer Graphics
•
•
•
•
•
1. Entertainment — Movies, games, animation.
2. Education — Visualizations in teaching complex subjects.
3. Simulation — Aircraft and driving simulators.
4. CAD/CAM — Design of vehicles, buildings, and machines.
5. GUI Design — Windows, icons, and menus in operating systems.
4. Architecture of Raster and Vector Display Systems
Raster Scan System: Works like a television. The screen is divided into pixels, and an
electron beam scans line by line (left to right, top to bottom). The intensity of each pixel is
controlled by a frame buffer storing pixel color values.
Example: Modern monitors and TVs are raster displays.
Figure Description: Imagine horizontal lines filling the screen — the beam lights up pixels
row by row.
Vector Scan System: Instead of scanning pixel by pixel, the electron beam directly draws
lines between specified coordinates. Used in early display systems and oscilloscopes.
Example: Old radar displays used vector displays to draw lines directly.
5. Color Lookup Table (CLUT)
A Color Lookup Table maps an index value (stored for each pixel) to an RGB color value.
It allows efficient memory usage and dynamic color changes without altering pixel data.
Example: Changing the palette in an 8-bit image modifies colors instantly.
6. Display Devices
•
•
•
•
•
•
•
Cathode Ray Tube (CRT): Uses an electron gun to illuminate phosphor-coated
screen. Types: Monochrome, Color CRT.
Direct View Storage Tube (DVST): Retains images without refreshing but cannot
be erased selectively.
Plasma Panel: Uses small gas cells that emit light when electrified.
LCD: Liquid crystals change alignment to block or allow light; requires backlight.
LED: Uses light-emitting diodes; efficient, bright, and durable.
Emissive Displays: Emit light (CRT, Plasma, LED).
Non-Emissive Displays: Rely on external light source (LCD).
7. Input Devices
Input devices allow user interaction with graphics systems. Common devices include:
•
•
•
•
•
•
•
1. Keyboard — for textual input.
2. Mouse — for pointing and selection.
3. Joystick — for controlling direction or motion in games.
4. Light Pen — detects light emitted from CRT pixels.
5. Digitizer — for drawing and capturing coordinates.
6. Touch Screen — combines display and input surface.
7. Scanner — converts hardcopy images to digital format.
Summary Points
•
•
•
•
•
Computer Graphics converts data into visual form.
Raster systems store images as pixel matrices; vector systems draw lines directly.
CLUT enhances color flexibility using indexed color mapping.
Modern displays mostly use emissive LED or non-emissive LCD technologies.
Input devices are essential for interactivity and design control.
Possible Exam Questions
•
•
•
•
•
1. Explain Raster and Vector display systems with diagrams.
2. Describe any four display devices with working principles.
3. What is a Color Lookup Table? Explain with an example.
4. Differentiate between emissive and non-emissive displays.
5. List and explain various input devices used in computer graphics.