SDF interpolation

[josemendez]

Hi!
Yeah that was the same idea I had in mind, but instead of generating full volume with 0 I thought about some kind of prost processing to construct tree that contains all possible branches from "flipbook".

Thank you for your feedback! So to make it work properly I would need to know vector field of movement, and that is not possible in current package without modification, correct?

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.

What you described makes sense, so I would need to have two SDF's interpolated, but on top of that I would need to calculate velocity of that movement and apply this to particles?

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

But except that, would that be very bad if movement of SDF surface was not huge?

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.

Maybe I should explain what I wanted:
The core idea is that I want to have collision of rod with some soft materials aka flesh, so I made softbody initially, I enabled surface collisions, but for some reason it's unstable, I guess shape constraint it too "strong" to keep rod depenetrated when pused against the surface, or perhaps this is related to collision itself? I think softbody uses triangles instead of tetrahedrons, not sure if this is huge difference?

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.

kind regards,