Jolt Physics — High-Performance Rigid Body Physics Engine

Introduction

Jolt Physics is a C++ rigid body physics library that prioritizes multi-core performance, determinism, and simulation stability. It was developed to meet the demands of AAA game production and has been battle-tested in titles like Horizon Forbidden West and Death Stranding 2.

What Jolt Physics Does

• Simulates rigid body dynamics with continuous collision detection
• Supports convex and concave shapes, height fields, and compound colliders
• Provides constraints including hinges, sliders, cones, and ragdolls
• Parallelizes the simulation pipeline across multiple CPU cores
• Delivers deterministic results for the same input across platforms

Architecture Overview

Jolt splits the simulation into broad-phase (spatial partitioning via a layered bounding volume hierarchy), narrow-phase (GJK/EPA for collision detection), and constraint solving (an iterative velocity solver). Work is distributed across threads using a job system with fine-grained tasks, enabling near-linear scaling on multi-core CPUs.

Self-Hosting & Configuration

• Build with CMake on Windows, macOS, Linux, Android, iOS, and WebAssembly
• Add as a submodule or use CMake FetchContent in your project
• Configure simulation layers and collision filters via the object layer system
• Tune solver iterations, gravity, and time step in PhysicsSystem settings
• Optional debug renderer draws wireframe shapes for visual debugging

Key Features

• Multi-core job system scales simulation across all available CPU cores
• Deterministic simulation produces identical results given identical input
• Continuous collision detection prevents fast objects from tunneling through geometry
• Soft body support for cloth and deformable object simulation
• Compact memory layout designed for cache efficiency

Comparison with Similar Tools

• Bullet — Mature and widely used; Jolt is newer with better multi-core scaling
• PhysX — NVIDIA proprietary; Jolt is MIT-licensed and vendor-independent
• Havok — Commercial middleware; Jolt is free and open source
• Box2D — 2D only; Jolt is a full 3D rigid body engine
• Rapier — Rust-based physics; Jolt targets C++ with proven AAA production use

FAQ

Q: Is Jolt Physics production-ready? A: Yes. It ships in AAA games including Horizon Forbidden West and Death Stranding 2 by Guerrilla Games and Kojima Productions.

Q: Does Jolt support soft bodies? A: Yes. Jolt includes soft body simulation for cloth, pressure-based volumes, and deformable meshes.

Q: Can I use Jolt with engines other than custom ones? A: Community integrations exist for Godot, Bevy, and other engines. The library is engine-agnostic and designed for easy embedding.

Q: How does determinism work across platforms? A: Jolt avoids platform-dependent floating point behavior and guarantees bitwise identical results when given the same input and configuration, regardless of operating system.

Sources

• https://github.com/jrouwe/JoltPhysics
• https://jrouwe.github.io/JoltPhysics/