There have been a few attempts to replace VPhysics (Valve's library built on top of Havok: https://vghe.net/source-engine.html#vphysics https://vghe.net/source-

There have been a few attempts to replace VPhysics (Valve's library built on top of Havok: https://vghe.net/source-engine.html#vphysics https://vghe.net/source-engine.html#vphysics They seem fairly functional but not fully drop-in replacements.