JoltPhysics

A few years ago, as someone who has worked on physics engines for robotics simulations, I would have agreed with you. But now a lot of people are doing greenfield physics engines for games and having it work out pretty well. There's a ton of established academic and conference literature in the area now and it's not nearly as scary as it used to be. For example, Horizon: Forbidden West uses a custom physics engine that started out as one of the core dev's fun side projects: https://github.com/jrouwe/JoltPhysics Physics engines (at least game quality physics engines) are starting to drift in to "solved problem" territory and there's enough literature now that you can get something reasonable going yourself after doing some weekend reading. Edit to add: Godot has had its own engine available for a long time, so it's not a totally new effort

GJK handles closest points (and distance, separating axis) between two non-overlapping convex shapes. Once convex shapes penetrate, you can use EPA, the Expanding Polytope Algorithm, invented Gino van den Bergen (while we were working together at NaN/Blender, around 20 years ago). See also http://dtecta.com/publications and check out this recent implementation in C++ for both GJK and EPA is in Jolt Physics (used in the game Horizon Forbidden West): https://github.com/jrouwe/JoltPhysics/tree/master/Jolt/Geome...