Particle System

A simple interactive particle system built with C++ and SDL2. Click anywhere in the window to spawn colorful particles that bounce off walls and fade over time.

Features

• Click to spawn - Creates a burst of 25 particles at the mouse position
• Physics simulation - Gravity, velocity, and bounce mechanics
• Wall collision - Particles bounce off all four edges with energy dampening
• Fade effect - Particles gradually become transparent as they age
• Automatic cleanup - Dead particles are removed to maintain performance

Requirements

• C++ compiler (g++ or clang++)
• SDL2 library

Installation

macOS

brew install sdl2

Ubuntu/Debian

sudo apt-get install libsdl2-dev

Fedora

sudo dnf install SDL2-devel

Windows

Download SDL2 development libraries from https://libsdl.org and configure your compiler's include/library paths.

Building

Compile the project using:

g++ -o particles particles.cpp $(sdl2-config --cflags --libs)

Or with clang:

clang++ -o particles particles.cpp $(sdl2-config --cflags --libs)

Running

./particles

Controls

Input	Action
Left Click	Spawn particles at cursor
ESC	Quit
Close Window	Quit

How It Works

Code Structure

The program is organized into several sections:

1. Particle struct - Holds data for each particle (position, velocity, color, alpha, lifetime)
2. spawnParticles() - Creates a burst of particles with random directions and colors
3. updateParticles() - Applies physics each frame (gravity, movement, bouncing, fading)
4. main() - Initializes SDL, runs the game loop, handles input

Physics

Each frame, particles are updated with basic Euler integration:

velocity.y += gravity * deltaTime    // Apply gravity
position += velocity * deltaTime     // Move particle

When a particle hits a wall, its velocity is reversed and reduced by the bounce damping factor (30% energy loss per bounce).

Rendering

Particles are drawn as 4x4 pixel squares with alpha blending enabled. As a particle ages, its alpha value decreases proportionally, creating a smooth fade-out effect.

Customization

Edit these constants at the top of particles.cpp to change behavior:

Constant	Default	Description
WINDOW_WIDTH	800	Window width in pixels
WINDOW_HEIGHT	600	Window height in pixels
GRAVITY	500.0	Downward acceleration (pixels/sec²)
BOUNCE_DAMPING	0.7	Energy retained after bounce (0.0-1.0)
PARTICLE_LIFETIME	3.0	Seconds before particle fades completely
PARTICLES_PER_CLICK	25	Number of particles per click
SPAWN_SPEED	300.0	Initial particle velocity

Ideas for Modifications

• Change particle size in the render loop (currently 4x4 pixels)
• Add different particle shapes (circles, triangles)
• Implement particle trails
• Add keyboard controls to adjust gravity in real-time
• Create different spawn patterns (streams, explosions, fountains)
• Add particle-to-particle collision