(I’m not a Teardown dev!)

I tried this on a local project. It looks very jank and the math falls apart quickly. Unfortunately, using a fixed axis-aligned grid for rotating reference frames is not practical.

One to thing I wanted to try but didn’t, was to use dynamic axes. So once an entity is created (that is, a group of voxels not attached to the world grid), it gets its own grid that can rotate relative to the world grid. The challenge would be collision detection between two unaligned grids of voxels. Converting the group to a mesh, like Teardown does, would probably be the easiest and most effective way, unless you want to invent some new game-physics math!

This sounds like a fun thing to do simply for the pleasing global consistency, but the price you will pay is that the physics will inevitably look weird since all our intuition is for smooth space. In this sense it's like those games that try to put you into a 4D space, where the weirdness is sort of the point.

Not sure what you mean with the claim that Newtonian Mechanics doesn't work in discretised space? I'm know there are plenty of codes that discretise space and solve fluid mechanical problems, and that's all Newtonian physics.

Of course you need a quite high resolution (compared to the voxel grid in teardown) when you discretise for it to come out like it does in reality, but if you truly want discretised physics on the same coarse scale as the voxels in teardown you can just run these methods and accept it looks weird.

(not a teardown dev)

i had brainstormed a bit a similar problem (non world aligned voxels "dynamic debris" in a destructible environment. One of the ideas that came through was to have a physics solver like the physX Flex sdk.

https://developer.nvidia.com/flex * 12 years old, but still runs in modern gpus and is quite interesting on itself as a demo * If you run it, consider turning on the "debug view", it will show the colision primitives intead of the shapes.

General purpose physics engine solvers arent that much gpu friendly, but if the only physical primitive shape being simulated are spheres (cubes are made of a few small spheres, everything is a bunch of spheres) the efficiency of the simulation improves quite a bit. (no need for conditional treatment of collisions like sphere+cube, cube+cylinder, cylinder+sphere and so on)

wondered if it could be solved by having a single sphere per voxel, considering only the voxels at the surface of the physically simulated object.

You could project your dynamic objects to world coordinates, but it would look pretty wonky for small objects. A grid is just fundamentally not going to look very physical.

Maybe you could simulate physics but completely constrain any rotation? Then you’d have falling stuff, and it could move linearly (still moving in 3d space but snapping to the world grid for display purposes)?