# Box3D — High-Performance 3D Physics Engine for Games

> Box3D is a 3D physics engine by Erin Catto, the creator of Box2D, offering fast rigid-body simulation with modern solver algorithms for game and simulation developers.

## Install

Save in your project root:

# Box3D — High-Performance 3D Physics Engine for Games

## Quick Use
```c
// Link against box3d library
#include "box3d/box3d.h"

b3WorldDef worldDef = b3DefaultWorldDef();
worldDef.gravity = (b3Vec3){0.0f, -9.81f, 0.0f};
b3WorldId world = b3CreateWorld(&worldDef);

// Step the simulation
b3World_Step(world, 1.0f / 60.0f, 4);
```

## Introduction
Box3D is a 3D physics engine written in C by Erin Catto, the renowned creator of Box2D. It extends the proven design principles of Box2D into three dimensions, providing fast and accurate rigid-body simulation for games, robotics, and interactive applications.

## What Box3D Does
- Simulates 3D rigid-body dynamics with collision detection and response
- Supports common 3D shapes (boxes, spheres, capsules, convex hulls)
- Provides joints and constraints for articulated bodies and mechanisms
- Handles continuous collision detection to prevent tunneling
- Delivers deterministic simulation results for consistent behavior

## Architecture Overview
Box3D follows a data-oriented design in pure C for maximum performance and portability. The broad phase uses a dynamic bounding volume hierarchy for spatial queries. The narrow phase computes contact manifolds using GJK and SAT algorithms. The solver uses a modern approach with warm starting and sub-stepping for stable, accurate constraint resolution.

## Self-Hosting & Configuration
- Build with CMake on any platform with a C11 compiler
- Link as a static or shared library into your game engine or application
- Configure world gravity, solver iterations, and time step size at initialization
- Tune collision filtering using category and mask bits
- Sample applications included for testing and reference

## Key Features
- Written in pure C for maximum portability and performance
- Data-oriented design with cache-friendly memory layouts
- Multithreaded island solving for parallel simulation
- Continuous collision detection prevents fast-moving objects from tunneling
- Created by the author of Box2D with decades of physics engine expertise

## Comparison with Similar Tools
- **Bullet Physics** — Mature and feature-rich but complex C++ API; Box3D is simpler and C-based
- **PhysX (NVIDIA)** — High performance but proprietary with complex licensing; Box3D is open source
- **Rapier** — Rust-based physics engine; Box3D targets C for broader engine integration
- **Jolt Physics** — Modern C++ engine; Box3D offers a simpler C API with similar performance goals

## FAQ
**Q: Is Box3D related to Box2D?**
A: Yes. Both are created by Erin Catto. Box3D extends the design philosophy of Box2D into three dimensions.

**Q: Can I use it with Unity or Unreal?**
A: Not directly, but the C API can be integrated as a native plugin in any engine.

**Q: Is it production-ready?**
A: Box3D is in early development. Check the repository for current stability status.

**Q: Does it support soft bodies or cloth?**
A: No. Box3D focuses on rigid-body dynamics. Use a dedicated solver for deformable bodies.

## Sources
- https://github.com/erincatto/box3d
- https://box2d.org

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Author: AI Open Source