SDF interpolation

[Qriva0]

Correct. Off the top of my head, there's no easy and accurate way to calculate a surface movement/velocity vector from two SDFs, as you'd need to get correspondences between points in each SDF to do that. Take this with a grain of salt though as I've never actually tried it out.

That's the gist of it, yes. You'd need to somehow calculate and store velocities as well, to get proper collisions.

You are right this is not trivial if we want to know exact point to point movement, I thought about simplification along the normals, so I know time between flipbook frames and I take that to calculate velocity from delta. I would compare it to tweaking collider thickness. and taking that delta as velocity.

Depends on how much "bad" you're willing to tolerate in your case. You would get no friction at all (since the SDF velocity is zero) and you'd get some popping/jitter as the SDF surface moves around pushing particles out of its way. If all you want is to roughly keep particles out of the SDF volume, it may be ok. If you want something resembling actual collisions then I would discard the idea.

Yeah, no friction is problematic and to be honest depenetration can cause sagnificant "jumps". I might try to use collider thickness to simulate and see how it actually behaves.

The softbody implementation in Obi is meshess, as it uses shape matching. For surface collisions it uses triangles. However keep in mind that surface collisions are just a cheap approximation of true edge vs triangle vs point collisions, they may not offer 100% smooth collision detection under all circumstances.

I'd need to know more about your use case to give useful feedback. Rod vs softbody collisions should just work even without surface collisions, as long as the rod and the softbody are sufficiently sampled with particles. Now, if either of them uses sparse sampling (meaning there's gaps in between particles) surface collisions should work except in scenarios involving large forces or high velocities.

My rod is not dense, but I used surface for both, just to be sure particles do not penetrate the surface, for cloth it works really well, so I expected something similar from softbodies, but in reality it did not work so well. I can't send videos here, so I am going to send one to your email.