JoltPhysics

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# Jolt Physics

A multi core friendly rigid body physics and collision detection library. Suitable for games and VR applications. Used by Horizon Forbidden West and Death Stranding 2: On the Beach.

[![Horizon Forbidden West Cover Art](https://jrouwe.nl/jolt/Horizon_Forbidden_West.png)](https://www.playstation.com/en-us/games/horizon-forbidden-west/)
[![Death Stranding 2 Cover Art](https://jrouwe.nl/jolt/Death_Stranding_2.png)](https://www.playstation.com/en-us/games/death-stranding-2-on-the-beach/)

|[![Ragdoll Pile](https://img.youtube.com/vi/pwyCW0yNKMA/hqdefault.jpg)](https://www.youtube.com/watch?v=pwyCW0yNKMA)|
|:-|
|*A YouTube video showing a ragdoll pile simulated with Jolt Physics.*|

For more demos and [videos](https://www.youtube.com/watch?v=pwyCW0yNKMA&list=PLYXVwtOr1CBxbA50jVg2dKUQvHW_5OOom) go to the [Samples](Docs/Samples.md) section.

## Design considerations

Why create yet another physics engine? Firstly, it has been a personal learning project. Secondly, I wanted to address some issues that I had with existing physics engines:

* Games do more than simulating physics. These things happen across multiple threads. We emphasize on concurrently accessing physics data outside of the main simulation update:
	* Sections of the simulation can be loaded / unloaded in the background. We prepare a batch of physics bodies on a background thread without locking or affecting the simulation. We insert the batch into the simulation with a minimal impact on performance.
	* Collision queries can run parallel to adding / removing or updating a body. If a change to a body happened on the same thread, the change will be immediately visible. If the change happened on another thread, the query will see a consistent before or after state. An alternative would be to have a read and write version of the world. This prevents changes from being visible immediately, so we avoid this.
	* Collision queries can run parallel to the main physics simulation. We do a coarse check (broad phase query) before the simulation step and do fine checks (narrow p