2D Physics

This project is a modular physics simulation environment developed using Java Swing. It provides an interactive platform to explore Newtonian Mechanics, Rigid Body Collisions, and Smoothed Particle Hydrodynamics (SPH) for fluid simulation.

The primary objective of this project is to demonstrate how complex physical phenomena can be modeled from scratch using pure Java, without relying on external physics libraries.

Main Features

1. Rigid Body Physics

• Collision Resolution: Implements impulse-based collision logic with mass-weighted position correction to prevent particle overlapping.
• Momentum: Conservation of momentum for both elastic and inelastic collision scenarios.
• Environmental Interaction: Robust floor and wall collision detection.

2. Liquid Physics (SPH) & Optimization

• Fluid Dynamics: Real-time water simulation using the Smoothed Particle Hydrodynamics (SPH) algorithm.
• Internal Forces: Density-based Pressure (repulsion) and Viscosity (friction) calculations.
• Spatial Hashing (Grid System): An optimized grid-based neighbor search system that reduces complexity from $O(N^2)$ to approximately $O(N)$. This enables fluid simulation of hundreds of particles with high performance.

3. Interactive Interface & Controls

• Real-time Parameters: On-the-fly adjustment of gravity, mass, and radius values.
• Dynamic Interaction: Ability to grab, drag, and toss particles using the mouse, or spawn new objects with the 'S' key.
• Modes: Seamless switching between individual rigid bodies and large liquid volumes.

Technical Overview

• Integration: Utilizes the "Semi-implicit Euler" method for stable motion calculations.
• Vector Mathematics: All physical calculations are processed through a custom Vector2 library.
• Performance: Proximity tests for SPH calculations are optimized via a custom HashMap-based Grid system.

Controls and Inputs

Input	Action
Mouse Drag	Grabs and tosses particles.
'S' Key	Spawns a rigid particle at a random location.
Gravity Field	Sets the global downward force (N).
Radius Field	Determines the size of objects (px).
Toggle Liquid	Clears the scene and initializes the SPH fluid simulation.

Contributing

This is an open-source educational project, and contributions are highly encouraged. If you would like to enhance the physics engine, improve performance, or add new features, please follow the guidelines below.

Areas for Contribution:

• Physics Engine Improvements: Implementation of inter-particle friction or Verlet Integration.
• Fluid Enhancements: Surface tension calculations or presets for different liquid types (e.g., honey, oil).
• Visualization: Integration with OpenGL (LWJGL) instead of Java 2D for advanced rendering.
• Bug Fixes: Improving edge-case handling in current collision detection algorithms.

How to Contribute:

1. Fork the repository.
2. Create a new branch for your feature (git checkout -b feature/AdvancedPhysics).
3. Commit your changes (git commit -m 'Add: Inter-particle friction').
4. Push to the branch (git push origin feature/AdvancedPhysics).
5. Open a Pull Request.

Installation and Execution

1. Requirement: Ensure JDK 8 or higher is installed on your system.
2. Compilation:

   javac *.java

3. Execution:

   java SimulationApp