Two-Phase Constraint Solving

I am trying to re-create the VR locomotion of the game Lone Echo. I found this great talk on the GDC archive https://www.gdcvault.com/play/1024446/It-s-All-in-the
They mention to achieve the designer physics they basically just move the player if there is an interaction with the world and the object you are “holding”.

The detailed explanation goes a bit above my head but from what I can gather they simulate everything twice on the physics side. Once with the player having infinite mass and once with normal mass. Then they see if there were violated constraints and use that info to move the player. To me, this seems like you need quite the low-level access to the physics engine to get this info and functionality. I was wondering how can this be achieved in Godot. I can see there are 3rd party physics libraries like Jolt that might be the answer, but unsure how to get the relevant info.

It should be possible,

You can get access to physics objects asking the physics server for it with the physics objects RID. And you can have custom integrators.

I did look at the slides, but wasn’t really sure why you would would need to do it like that.

I played with physics constraints. I had much greater success in Unity but in Godot the fine-grain control is minimal. I was wondering if there is a way to have a custom constraint implemented. I will be happy with writing some GDExtention code.