Wanted to share Mathias Müllers latest video about his XPBD physics system. He has started a new series about how to create a XPBD based rigid body simulator. The code is written in Java, and you can test it in your browser. Müller is a researcher working at NVIDIA, who thankfully shares this knowledge for free. I believe Unreal Engine uses XPBD for soft bodies and cloth. Would be cool to get XPBD physic for rigid bodies as well since it can handle constraints better, especially high mass ratio constraints.
YouTube video presenting the code and series:
22 - How to write a rigid body simulator