Computer graphics
computer graphics (CG) is the field of creating images and animations using computers. It’s a vast and interdisciplinary field that combines elements of:
Physics: Understanding light, reflection, refraction, and materials is important for realistic rendering.
Mathematics: Linear algebra, calculus, geometry, trigonometry are fundamental for transformations, projections, and lighting calculations.
Computer Science: Data structures, algorithms, software engineering, and programming are essential for implementing graphics systems.
Art: Principles of design, color theory, composition, and aesthetics are crucial for creating visually appealing and effective graphics.
Types of Computer Graphics (Computer graphics)
1. Raster Graphics (Bitmap Graphics)
- Image made of small dots called pixels.
- Common for photos , scanned images , digital painting .
- Quality depends on resolution (DPI,PPI).
- Editing is pixel-based. (Computer graphics)
Examples: JPEG, PNG, BMP, GIF.
2. Vector Graphics (Computer graphics)
- Uses mathematics equations to draw shapes (lines, curves, polygons).
- Scalable without losing quality (infinite zoom possible).
- Best for logos , illustrations, CAD drawings.
Examples: SVG, EPS, PDF, AI files.
3. 2D Graphics
- Deals with flat images (X and Y axis).
- Used in UI design, simple games, charts, diagram.
- Includes 2D transformations(Translation, Rotation, Scaling).
Examples: Paintings, cartoons, floor plans.
4. 3D Graphics
- Represents objects with depth (X, Y, Z axis).
- Used in games, simulations, 3D modeling, movies.
- Involves 3D transformations, projections, lighting, shading.
Examples: 3D models, VR/AR apps, 3D animations. (Computer graphics)
5. Interactive Graphics
- User can interact with graphics in real-time.
- Common in video games, simulations, design software.
- Requires fast rendering and user input handling.
Examples: AutoCAD, video games, VR simulations. (Computer graphics)
6. Non-Interactive Graphics (Passive)
- Graphics are static static; no user interaction.
- Used in print media, display boards, presentations.
Examples: Printed posters, static images.
Summary Table:
| Type | Key Points |
|---|---|
| Raster Graphics | Pixel-based, resolution dependent |
| Vector Graphics | Shape-based, scalable without quality loss |
| 2D Graphics | Flat images (X, Y), simple charts, UI, 2D games |
| 3D Graphics | Depth (X, Y, Z), realistic models, animations |
| Interactive Graphics | User can interact (games, CAD, simulations) |
| Non-Interactive Graphics | Static visuals without user interaction |
1. Frame Buffer
Definition:
A Frame Buffer is a memory area that stores pixel data (color values) to be displayed on the screen. It holds information like:
- Color of each pixel.
- Intensity (brightness).
- Depth (for 3D graphics).
Key Points:
- Located in RAM or VRAM (Video RAM).
- Acts as a digital canvas for the computer to draw images.
- The content of the frame buffer is continuously sent to the display screen.
- The more bits per pixel (bpp), the better color quality (e.g., 8-bit, 16-bit, 24-bit color).
Example:
- For a screen of 1920×1080 pixels with 24-bit color depth, the frame buffer stores: (Computer graphics)
2. Video Controller
Definition:
A Video Controller (or Graphics Controller) is a hardware device that:
- Reads data from the frame buffer.
- Generates the video signal for the display device (like monitor, LCD, LED)
- Controls the timing and synchronization of the display.
Functions of Video Controller:
- Converts pixel data (from frame buffer) into signals.
- Controls refresh rate (like 60Hz, 120Hz).
- Manages color output, resolution , and sync signals.
- Acts as an interface between CPU, GPU, Frame Buffer, and Display Screen.
Components:
- Display Registers (store current settings like resolution, refresh rate).
- Digital to Analog Converter (DAC) (for analog displays like CRT monitors).
- Timing Circuits (for scan control). (Computer graphics)
- GPU (Graphics Processing Unit) may be part of the video controller in modern systems.
Diagram: Frame Buffer & Video Controller Relationship
+------------------+ +---------------------+ +-----------------+
| | | | | |
| CPU / GPU | -----> | Frame Buffer | -----> | Video Controller |
| | | (Pixel Data Memory) | | (Signal Generator) |
+------------------+ +---------------------+ +-----------------+
|
|
+-----------------+
| Monitor / |
| Display Device |
+-----------------+
Points and Lines in Computer Graphics
A) Point:
1–A point represents a single pixel on the screen.
2–Defined by its coordinates (x, y) in 2D or (x, y, z) in 3D.
B)Line:
A line is a collection of connected points between two coordinates.
Defined by starting point (x1, y1) and ending point (x2, y2).
Equation of line: y = mx + c, where:
- m = slope = (y2 – y1) / (x2 – x1)
- c = y-intercept.
DDA (Digital Differential Analyzer) Algorithm
Definition:
DDA is an incremental scan-conversion algorithm. It calculates pixel positions along a line by incrementing one coordinate and calculating the other. (Computer graphics)
Algorithm Steps (DDA-1):
- Calculate differences:
dx = x2 – x1,
dy = y2 – y1. - Calculate steps:
steps = max(|dx|, |dy|). - Calculate increments:
Xinc = dx / steps,
Yinc = dy / steps. - Initialize starting point:
(X = x1, Y = y1). - For each step:
- Plot (round(X), round(Y)).
- Update X = X + Xinc.
- Update Y = Y + Yinc.
Example (DDA-2):
For line from (2, 3) to (10, 8):
- dx = 8, dy = 5.
- steps = 8.
- Xinc = 1, Yinc = 0.625.
- Start plotting from (2, 3), increment X and Y for each step.
Bresenham’s Line Drawing Algorithm
Definition:
Bresenham’s algorithm is an efficient line drawing algorithms that uses only integer calculations (no floating points).
Algorithm Steps (Bresenham-1):
- Calculate dx = x2 – x1, dy = y2 – y1.
- Initialize decision parameter:
p = 2dy – dx. - For every x from x1 to x2:
- Plot (x, y).
- If p < 0, next pixel is (x+1, y), update p = p + 2dy.
- Else, next pixel is (x+1, y+1), update p = p + 2dy – 2dx.
Example (Bresenham-2):
For line from (2, 2) to (7, 5):
- dx = 5, dy = 3.
- Initial p = 2dy – dx = 2*3 – 5 = 1.
- Plot pixels step by step using p values.
Midpoint Circle Drawing Algorithm
Definition:
An efficient method to draw a circle by calculating pixel positions in one octant and reflecting them to other parts of the circle.
Formula & Steps (Midpoint Circle-1):
- Start at (x = 0, y = r).
- Initial decision parameter:
p = 1 – r. - For each x from 0 to y:
- Plot symmetric points in 8 octants.
- If p < 0:
- Next point is (x+1, y).
- p = p + 2x + 3.
- Else:
- Next point is (x+1, y-1).
- p = p + 2x – 2y + 5.
Example with Definition (Midpoint Circle-2):
- For a circle of radius r = 5.
- Start with (0, 5).
- Compute p = 1 – 5 = -4.
- Plot points and update p for each step.
- Reflect points in all 8 symmetrical positions.
Summary Table
| Algorithm | Key Points |
|---|---|
| DDA Algorithm | Uses floating point increments, simple but slower due to real number calculations. |
| Bresenham’s Algorithm | Uses only integer operations, faster and efficient for raster devices. |
| Midpoint Circle Algorithm | Efficiently plots circle points using symmetry and integer calculations. |
also read this :- Introduction to Operating System (OS)
