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Comment by Waterluvian | Hacker News Reader

Playing with 3DS Max 5 in high school was such a “portal to the future” feeling. I loved the physics and cloth sims.

But come to think of it… has anyone ever seen a cloth simulation where the cloth can be more realistically rolled up or knotted, twisted, or otherwise doing things requiring a sense of volume and mass?

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[SIGGRAPH 2017] Anisotropic Elastoplasticity for Cloth, Knit and Hair Frictional Contact: https://vimeo.com/219585631

If that doesn't do it for you, there's a lot more options in the SIGGRAPH paper list at https://kesen.realtimerendering.com/

Absolutely unreal some of those demos.

Actually they're absolutely real looking ;p

But yeah, very mind blowing.

For the Anisotropic Elastoplasticity for Cloth, Knit and Hair Frictional Contact - 2 minutes per frame. Hopefully we'll see things like this in realtime soon.

As an ex-3D developer, these videos are wild. Thank you.

Exactly what I was seeking. Thank you. That shag carpet sim is incredible.

Straight from the oven (paper from SIGGRAPH 2023): "Multi-Layer Thick Shells" (https://youtube.com/watch?v=z1Wc5DvC2Wk) Extends the FEM model to accommodate for thick shell-like structures, like yoga mats, leather, and wrinkles on matrices.

Also you might want to check out the IPC papers (particularily C-IPC, since you said you're interested in cloth: https://www.youtube.com/watch?v=jvBSDXxsgRA). A new class of simulation methods has arisen over the years which allow you to simulate detailed collisions in an incredibly robust way (though computation time is still an issue).

> though computation time is still an issue

This is what I got hung up on. I was doing some independent research on real-time cloth simulation for sailboats and I reached the conclusion that the physically accurate techniques are not real-time. I was looking at simulating tensions applied at specific vertices of the sail, the stiffness of the cloth, wind pressures, etc... and I gave up on finding anything that was doing it in real-time.

Am I wrong? Or is there a SIGGRAPH paper I haven't found yet :P

Have you looked into Small Step XPBD (introduced in the paper "Small Steps in Physics Simulation ")? It's the most efficient nonlinear dynamics integrator/solver I've come across, and luckily one of the simplest, too! (Keeping in mind that simplest nonlinear solver is a relative metric.) I've been able to simulate very stiff materials like bone by updating the sim at 6000 steps/second. The exact number of steps/second you'll need will depend on both the desired spatial resolution and physical accuracy of your sails, but I wouldn't be surprised if 6000 steps/second is more than sufficient. And computers are fast enough where you could simulate quite a few large, detailed sails at that rate in realtime.

Thanks for that link, I had not seen this paper before. I will add this to the backlog of things to try!

The channel @TwoMinutePapers on YouTube sometimes reports on progress in this area.

See this playlist: https://www.youtube.com/playlist?list=PLujxSBD-JXgnnd16wIjed...

Back when I was at Pixar, I remember hearing a lot about the cloth sims for Brave (2012). The clothing was heavily layered, with each layer adding volume. Here's one public article:

https://pixartimes.com/2012/04/09/close-up-the-amazing-desig...

"To achieve the mass of Fergus' kilt, the drape going across his chest has eight layers of cloth folded over and interacting with each other and other garments. The left, right and back sides of the drape have six layers each."

In motion:

https://www.youtube.com/watch?v=T1SBjAuMN6A