libfive is unusual in the SDF space in that it doesn't assume Euclidean space, or even Lipshitz continuity! It uses interval arithmetic, so its evaluation is conservative by construction; shapes with weird SDFs may evaluate more slowly, but they won't be wrong.

This means that you can go wild with geometric and coordinate transformations – even weird things like twisting or attract/repel will work fine.

(the only requirement is C0 continuity, which is the bare minimum; otherwise, a point could be both inside and outside the shape depending on which direction you approach it from)