The C++ physics engine behind robot backflips and VR

What it does

Bullet3 is the official C++ source for real-time collision detection and rigid-body dynamics. It simulates physics for games, visual effects, VR, robotics, and machine learning. The library asks only for a C++ 2003 compiler and runs on virtually every platform that has one, including iOS and Android.

The interesting bit

Despite its vintage C++ core, the project now steers most users toward PyBullet—Python bindings that wrap the engine for robotics and reinforcement learning. There is also an experimental OpenCL path that can run the entire collision pipeline and rigid-body solver on a GPU, though it demands a high-end desktop card and is notoriously picky about drivers.

Key highlights

• Permissive zlib license across the entire codebase
• Cross-platform to a fault: tested on Windows, Linux, macOS, iOS, and Android
• Includes a VR sandbox for HTC Vive and Oculus Rift with shared-memory networking
• Entire collision and dynamics pipeline can execute on GPU via experimental OpenCL
• C++ 2003 requirement means it builds on compilers old enough to vote

Caveats

• The GitHub issue tracker is closed because it was flooded with support questions; discussion has moved to the PyBullet forums
• OpenCL acceleration is explicitly experimental: it does not work on OpenCL CPU devices, and kernel compilation failures on various drivers remain unresolved

Verdict

Use this if you need a battle-tested physics backend with extreme portability, or if you are building robotics and RL pipelines through PyBullet. Skip the experimental GPU path unless you enjoy debugging OpenCL kernel compilation errors.