Show HN: Soft Body Jiggle Physics | Hacker News Reader

Show HN: Soft Body Jiggle Physics

github.com

52 pointsvesperance21 comments

A simple and fundamental standard for dynamic soft body dynamics.

Nice to see someone else doing physics in the browser. And this looks well put together, keeping the engine dependency free and separate from the renderer is a good call, that is what makes it easy to reuse in Three or Babylon.

One question: how does it hold up when the framerate changes? Spring jiggle like this usually either blows up or feels different when the timestep moves around. Are you using a fixed timestep, or just relying on the damping to keep it stable?

> when the timestep moves around

Why would the physics timestep move around? Typically you keep that fixed and separate, especially not locked to the display framerate, physics get really wonky then regardless of what you do.

It depends on what you're simulating. A lot of what you'd use soft-body sims for run as a shader on a GPH - think hair, or a smirt - as long as it looks good, that's good enough, because it doesn't have physics interactions on other objects. So it's more natural to just use the frame rate steps, with a delta-t if necessary.

The accumulator pattern keeps simulations stable in the face of variable frame rate. Accumulate the frame dt into an accum variable. If accum>fixed_physics_dt then step_physics until false. I'm assuming the author did something like that because it's standard practise.

https://www.gafferongames.com/post/fix_your_timestep/

Well, as long as the step rate remains well above the Nyquist limit? Otherwise, your simulation will start to have something akin to aliasing errors.

That is one place where an analytical solution is a benefit, even if it is a bit less realistic. You just have a position(t) parametric function you can evaluate when rendering sporadically.

Could be used for soft sea fish models

Nice donut in the demo, but would love to see a human model for a more fun demo :) Ideally with a proper weight map for the different body parts too, seems well done enough that you could get really close to something realistic.

That's probably the intent given the link in their github bio

Huh, might seem so, although this seem unrelated but obvious the domains are... Similar.

Wish author wasn't such a chicken if it was intended for body parts, show the demo in the README, I think it's still legal isn't it?

There are much better soft-body sims out there to jack it to, if you are so inclined.

A reference would be greatly appreciated, to take inspiration from. This was a simple project, trying to push some simple and re-useable standard.

There are multiple geometries in the demo, the last is a highly detailed human anatomy. https://xloveee.github.io/jiggle-physics/

I had vastly different expectations, though I suppose this could lead to them..

Check the github user profile ;)

why would a "live cam show" company need jiggle physics?

Doing the lord’s work, advancing the human race forward.

Looks well documented. I applaud the author for not just sharing code, but taking the time to teach how to use it and how it was made.

I dunno, the readme is clearly LLM vomit. It's hard to praise docs that might not even have been read yet.

Seems like a contradictive reply, have you given it a read ? Yes it's a skimmed over LLM written readme.

> License

> Use freely.

How valid is that as a license?

Another example of the adult entertainment industry driving critical technology infrastructure forward...?

Makes me wonder: Does the adult entertainment industry have its own variant of the military's DARPA, or is it truly decentralized in its innovation and standards work? Haha

Something something men of culture

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