# Rapier — Fast 2D and 3D Physics Engine in Rust

> A high-performance open-source physics engine for rigid body simulation, collision detection, and joint constraints, with native Rust and JavaScript/WASM bindings.

## Install

Save in your project root:

# Rapier — Fast 2D and 3D Physics Engine in Rust

## Quick Use
```bash
# Add to your Rust project
cargo add rapier3d
# Or use in JavaScript via WASM
npm install @dimforge/rapier3d
```

## Introduction
Rapier is a set of 2D and 3D physics simulation libraries written in Rust with first-class WebAssembly support. It provides rigid body dynamics, collision detection, and joint constraints suitable for games, robotics simulations, and interactive applications.

## What Rapier Does
- Simulates rigid body dynamics with gravity, forces, and impulses
- Detects collisions between convex shapes, trimeshes, and heightfields
- Supports joints and constraints including revolute, prismatic, and fixed types
- Provides continuous collision detection (CCD) to prevent tunneling
- Exposes a deterministic simulation mode for lockstep multiplayer

## Architecture Overview
Rapier is built on the nalgebra linear algebra library and uses an island-based constraint solver with SIMD acceleration. The collision detection pipeline implements a broad-phase sweep-and-prune algorithm followed by narrow-phase GJK/EPA queries. The engine compiles natively to Rust targets and to WebAssembly via wasm-bindgen, sharing the same core simulation code across platforms.

## Self-Hosting & Configuration
- Add `rapier2d` or `rapier3d` as a Cargo dependency for Rust projects
- Use the `@dimforge/rapier2d` or `rapier3d` npm packages for JavaScript/WASM
- Configure gravity, timestep, and solver iterations via `IntegrationParameters`
- Enable CCD on fast-moving bodies to prevent objects passing through walls
- Use debug rendering with Bevy or other engines via the `rapier-debug-render` feature

## Key Features
- Cross-platform via native Rust and WebAssembly compilation
- Deterministic simulation for reproducible physics across clients
- Bevy integration through the `bevy_rapier` plugin for game development
- Event system for collision start/stop and contact force reporting
- Serialization support for saving and restoring simulation state

## Comparison with Similar Tools
- **Box2D** — mature 2D engine but C++ only, no built-in Rust or WASM support
- **Bullet** — feature-rich 3D engine but heavier and more complex API
- **PhysX** — high-performance but proprietary NVIDIA SDK
- **Cannon.js** — JavaScript-native physics but slower than WASM-based Rapier
- **Avian (formerly heron)** — Bevy-specific wrapper but Rapier powers it underneath

## FAQ
**Q: Can Rapier handle soft bodies or fluids?**
A: No. Rapier focuses on rigid body simulation. For soft bodies, consider complementary libraries.

**Q: Is the WASM build slower than native Rust?**
A: WASM performance is typically 1.5-3x slower than native, but still fast enough for real-time game physics in the browser.

**Q: Does Rapier support multithreading?**
A: Yes. The `parallel` feature enables rayon-based multithreaded simulation on native targets.

**Q: What game engines integrate with Rapier?**
A: Bevy (via bevy_rapier), Godot (via godot-rapier), and any engine that can call Rust or WASM code.

## Sources
- https://github.com/dimforge/rapier
- https://rapier.rs

---
Source: https://tokrepo.com/en/workflows/asset-ccb8bee3
Author: AI Open Source