Introduction to Computer Graphics

Introduction to Computer Graphics

Computer Graphics is the branch of computing that deals with creating, storing, and manipulating visual images using computers.

Applications

• Games 🎮
• CAD (Computer-Aided Design)
• Animation & Movies
• Data Visualization
• User Interfaces

Types of Computer Graphics

1. Raster Graphics (Bitmap)

• Image made of pixels
• Resolution dependent
• Example: Photos

• Realistic images
• Quality decreases when zoomed

2. Vector Graphics

• Image made of mathematical equations
• Resolution independent

• Scalable without loss
• Less realistic

3. 2D Graphics

• Flat images (x, y coordinates)

4. 3D Graphics

• Includes depth (x, y, z)

Graphic Displays

A. Random Scan Display (Vector Display)

Working

• Electron beam draws lines directly
• No pixel grid

Advantages

• High resolution for lines
• Smooth edges

Disadvantages

• Not suitable for filled images
• Expensive

B. Raster Scan Display

Working

• Screen divided into pixels
• Beam scans line by line (top to bottom)

Advantages

• Supports images, colors, shading
• Widely used (TV, monitors)

Disadvantages

• Aliasing (jagged edges)

Frame Buffer & Video Controller

Frame Buffer

• Memory that stores pixel values
• Each pixel has color/intensity info

Video Controller

• Reads data from frame buffer
• Sends signals to display device

Process:

1. Data stored in frame buffer
2. Video controller scans it
3. Image displayed on screen

Points and Lines

Point

• Basic unit → represented as (x, y)

Line

• Straight connection between two points
• Defined using slope:

$$m = \frac{y_2 - y_1}{x_2 - x_1$$

​​Line Drawing Algorithms

Why Needed?

To efficiently determine which pixels to turn ON to draw a line.

A. DDA (Digital Differential Analyzer)

Idea

• Increment x and y step by step

Steps

1. Calculate slope (m)
2. Increment x or y
3. Round values to nearest pixel

Advantages

• Simple

Disadvantages

• Floating point calculations
• Less efficient

B. Bresenham’s Line Algorithm

Idea

• Uses integer calculations only

Key Concept

• Decision parameter to choose nearest pixel

Advantages

• Faster than DDA
• No floating-point operations

Disadvantages

• Slightly complex

Circle Generating Algorithms

Equation of Circle:

$$x^2 + y^2 =$$

Methods

• Direct method (slow)
• Polar coordinates
• Midpoint algorithm (most efficient)

Midpoint Circle Algorithm

Idea

• Choose between two pixels based on midpoint

Key Concept

• Uses 8-way symmetry
• Only calculate one octant

Steps:

1. Start at (0, r)
2. Calculate decision parameter
3. Choose next pixel
4. Reflect to other octants

Advantages

• Fast
• Uses integer arithmetic

Parallel Version of Algorithms

Running algorithms simultaneously on multiple processors to improve speed.

Why Needed?

• Graphics require real-time rendering

Examples

1. Parallel Line Drawing

• Different segments drawn simultaneously

2. Parallel Circle Drawing

• Each octant processed in parallel

Advantages

• Faster rendering
• Efficient for large graphics

Challenges

• Synchronization
• Load balancing

Final Summary Table

Topic	Key Idea	Advantage
Raster Display	Pixel-based	Supports images
Random Scan	Line-based	Smooth lines
DDA	Incremental	Simple
Bresenham	Integer-based	Fast
Midpoint Circle	Symmetry	Efficient
Parallel Algorithms	Multi-processing	High speed

Concept Flow

Graphics System → Display → Frame Buffer → Algorithms → Shapes (Lines & Circles)