UE4 uses PhysX under the hood. It’s written in such a way that you could if you wanted to replace PhysX with whatever else (Bullet, Newton Dynamics etc) but it would be a bunch of work and you would be responsible for keeping your own fork up to date as new patches come out, which if you’ve rewritten something as core as physics integration may mean a lot of work to keep up to date with the rest of the engine.
The version of PhysX integrated into UE4 is based on the PhysX 3.3 SDK, if you want to search for information specific to the version that is integrated into UE4. Срок регистрации домена закончился