Particle Collision Simulator

Real-time 2D physics simulation demonstrating elastic collisions, gravity, friction, and momentum conservation

A physics engine built in Java that simulates realistic particle interactions with visual trails and interactive controls. Watch colorful particles bounce, collide, and interact following real physics principles!

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🎬 Demo

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✨ Features

Physics Simulation

• ⚛️ Elastic Collisions - Momentum and energy conservation between particles
• 🌍 Gravity Simulation - Toggle between Earth gravity and zero-gravity space mode
• 📉 Friction Modeling - Both kinetic and static friction with energy dissipation
• ⚖️ Mass-Based Interactions - Realistic physics based on particle mass and velocity
• 💥 Energy Loss - Configurable energy dissipation on collisions

Visual Effects

• 🌈 Colorful Particles - Each particle gets a random color
• ✨ Motion Trails - Beautiful trails that follow particle movement
• 💫 Particle Effects - Spark effects on high-velocity collisions (optional)
• 🎯 Hitbox Visualization - Toggle to see collision boundaries

Interactive Controls

• ➕➖ Add/Remove Particles - Dynamically spawn or remove particles
• ⏸️ Pause/Resume - Freeze the simulation at any time
• ⚡ Speed Control - Speed up or slow down the simulation
• 🚀 Boost Mode - Give all particles a random velocity boost
• 🔍 Debug View - Toggle hitbox visualization

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🎮 Controls

Key	Action
Q	Add a new particle
R	Remove a particle
P	Pause/Resume simulation
E	Give all particles a random boost
L	Speed up simulation (+10 ticks/sec)
K	Slow down simulation (-10 ticks/sec)
H	Cycle hitbox visualization (none → circular → rectangular)

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🚀 Getting Started

Prerequisites

• Java Development Kit (JDK) 8 or higher
• Any Java IDE (Eclipse, IntelliJ IDEA, VS Code) or command line

Installation & Running

1. Clone the repository

   git clone https://github.com/TaherJoudeh/collision-simulator.git
   cd collision-simulator

2. Compile

   javac -d bin src/program/*.java src/Input/*.java

3. Run

   java -cp bin program.Driver

Quick Start (Pre-compiled)

1. Download Square.jar from Releases
2. Double-click the JAR file or run:

   java -jar ParticleCollisionSimulator.jar

Quick Start (IDE)

1. Import the project into your IDE
2. Run Driver.java as a Java Application
3. Start experimenting with the controls!

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🔧 Configuration

Edit constants in DrawFrame.java to customize the simulation:

// Enable/disable space mode (no gravity)
public final static boolean inSpace = false;

// Enable/disable energy loss on collisions
public final static boolean energyLoss = true;

// Enable/disable particle effect sparks
public final static boolean particleSystemEnabled = false;

// Maximum number of particles allowed
public final static int MAX_PARTICLES = 100;

In Particle.java:

// Gravity acceleration constant
public final static float GRAVITY_ACCELERATION = 0.1f;

// Friction coefficients
public final static float MUIX = 0.2f;  // Kinetic friction X
public final static float MUIY = 0.2f;  // Kinetic friction Y
public final static float MUSX = 0.4f;  // Static friction X
public final static float MUSY = 0.4f;  // Static friction Y

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📐 Physics Model

Collision Detection

• Uses circular hitbox detection for accurate collision detection
• Distance-based algorithm: collision occurs when distance < radius1 + radius2

Momentum Conservation

m₁v₁ + m₂v₂ = m₁u₁ + m₂u₂

Where:

• m = mass
• v = initial velocity
• u = final velocity

Elastic Collision Equations

// Final velocity of particle 1
u1 = ((m1-m2)*v1 + 2*m2*v2) / (m1+m2)

// Final velocity of particle 2
u2 = (2*m1*v1 - (m1-m2)*v2) / (m1+m2)

Energy Dissipation

• Kinetic Friction: F = μₖ × m × g × v
• Static Friction: Prevents motion when kinetic energy < friction threshold
• Wall Collisions: Additional friction coefficient for boundaries

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🏗️ Project Structure

collision-simulator/
├── src/
│   ├── program/
│   │   ├── Driver.java           # Entry point
│   │   ├── DrawFrame.java        # Main game loop & rendering
│   │   ├── Window.java           # JFrame window setup
│   │   ├── Particle.java         # Main particle physics
│   │   ├── ParticleEffect.java   # Collision effect particles
│   │   ├── Position.java         # 2D position class
│   │   ├── Trail.java            # Motion trail system
│   │   └── TrailParticle.java    # Individual trail particles
│   └── Input/
│       ├── KeyInput.java         # Keyboard controls
│       └── MouseInput.java       # Mouse input (extensible)
└── README.md

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🎓 Educational Value

This simulator demonstrates fundamental physics concepts:

• Classical Mechanics: Newton's laws of motion
• Conservation Laws: Momentum and energy conservation
• Collision Theory: Elastic vs inelastic collisions
• Friction: Static and kinetic friction models
• Numerical Integration: Real-time physics simulation
• Computational Physics: Discrete time-step simulation

Perfect for:

• Physics students learning collision mechanics
• Game developers studying physics engines
• Anyone interested in computational physics

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🛠️ Technical Details

Built With

• Language: Java
• Graphics: Java AWT/Swing
• Game Loop: Custom tick-render cycle at 120 TPS

Performance

• Runs at 120 ticks per second
• Supports up to 100 particles simultaneously
• Uses BufferStrategy for smooth rendering
• Iterative collision resolution (3 iterations per frame)

Algorithms

• Collision Detection: O(n²) all-pairs checking
• Collision Response: Vector-based separation
• Trail System: Linked list with fixed capacity
• Particle Effects: Fading alpha transparency

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🐛 Known Limitations

• Collision detection is O(n²) - performance decreases with many particles
• Particles can occasionally overlap slightly under extreme conditions
• No spatial partitioning (quadtree/grid) for optimization
• Fixed simulation rate (requires modern CPU)

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📝 Physics References

This simulation is based on:

• Conservation of momentum in elastic collisions
• Classical Newtonian mechanics
• Coulomb friction model
• Standard collision response algorithms

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🎓 Development Journey

This simulator was built during my first year of college as a project to:

• Deepen understanding of classical mechanics
• Learn computational physics methods
• Explore game engine development
• Practice numerical simulation techniques

It represents the progression from basic programming to understanding how physics engines actually work under the hood.

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📄 License

This project is licensed under the MIT License - see the LICENSE file for details.

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👨‍💻 Author

Taher Joudeh

• GitHub: @TaherJoudeh

Project Timeline: College freshman (1st Year)

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🙏 Acknowledgments

• Built to understand physics engine development
• Inspired by classic particle simulation demonstrations
• Educational project exploring computational physics
• Part of learning journey from game development to engine development

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Made with ☕ and curiosity about physics | 1st year at college
Simulating the universe, one collision at a time! ⚛️