Physix2D

A lightweight 2D physics engine in C++, built as a learning journey and passion project.

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🚀 Getting Started

1. Build the library: ./build_lib.sh
2. Create a demo in the examples/src/my_demo folder and build it: ./examples/build_examples.sh
3. Run your demo: ./build/my_demo

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🎥 Demos

in the assets directory

colliding_balls.mp4

bouncing_balls.mp4

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✅ Development Roadmap

Phase 1: Core Physics + Visual Debug

• Vec2 (basic vector math)
• Body (circle-only: pos, vel, mass, radius)
• World (gravity + integration loop)
• DebugDraw (SFML/SDL/OpenGL)
• Falling ball demo 🌕
• Rain of balls demo 🌧
• Bouncing off ground demo ⬇️

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Phase 2: Collision Detection + Resolution

• Shape base class
• CircleShape, PolygonShape
• Collision detection (circle–circle, polygon–polygon)
• Contact manifold
• Simple solver (impulse resolution)
• Ball pit demo ⚪
• Box stack demo 📦
• Domino chain demo 🧱
• Ball inside box demo 🏀

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Phase 3: Joints & Constraints

• Joint base class
• RevoluteJoint, DistanceJoint
• Island solver
• Pendulum demo 🔗
• Rope bridge demo 🌉
• Ragdoll demo 🕺
• Newton’s cradle demo 🪀

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Phase 4: Advanced Collisions (Broad Phase + CCD)

• Broad-phase (dynamic tree, sweep & prune)
• Continuous collision detection (TOI)
• Bullet through stack demo 💥
• Loop track demo 🎢
• Stress test with thousands of objects 🌊

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Phase 5: Particles & Fluids

• Particle + ParticleSystem
• Particle contacts
• Water fountain demo 💧
• Sand pile demo 🏖
• Smoke effect demo ☁️
• Liquid in a box demo 🌊

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Phase 6: Soft Bodies (Rope, Cloth, Deformables)

• Rope, RopeJoint
• SoftBody, Cloth
• Rope swing demo 🪢
• Flag in wind demo 🏴
• Jelly cube demo 🍮
• Cloth + fluid interaction demo 🌊

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Phase 7: Polishing + Showcase

• World callbacks (begin/end contact)
• Profiler & memory manager
• Mixed scene demo 🎮
• Destructible bridge demo 🏗
• Tornado effect demo 🌀

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BONUS: Advanced Simulations -

• Clothe simulation
• Fluid simulation
• Smoke simulation

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