Eh? A (2.8) cloth simulation is ... "explodng?"

I’m using 2.8 and I really thought that this would be very simple. I’m trying to simulate a circularly-mounted curtain as it settles upon a bedframe below. So, I modeled and subdivided a cone and placed the top row of vertces into the “pin” vertex-group.

Well, to make a long story short, the completed simulation “went absolutely ape-shit.” The only way that I can try to describe what happened to the mesh is that it exploded, except that this might conjure up an image of some organized explosion. Except it was worse than that – vertices seemed to be tossed in every possible direction.

Also – the simulation seemed to take a rather extraordinary amount of time.

I’ve attached a blend-file … bake the simulation and watch it for yourself.
untitled.blend (1.8 MB)


I actually changed this file in one possibly-important way, and then was re-running the simulation, while I was posting the above: I removed exactly one pixel from the top-ring of the cone, thus the “pin” vertex-group.

With this single vertex removed, the simulation no longer “explodes,” but clearly it is also not “pinned in place.” The entire bolt of cloth drops rather crazily in a heap.

Furthermore, in the first few frames of the render, there are very-strange triangular shapes where, obviously, some vertices have been displaced nonsensically out-of–position . . .

:face_with_monocle: … could any part of this problem be that I am trying to use a closed shape – a cylinder?

(In the attached blend, I “broke” the pin-ring so that it’s no longer a ring, but the cloth shape remains a closed cylinder . … )

Please let me move this to the new “Cloth Hanging From A Ring” thread that I have since opened.

For those who have stumbled-upon this thread and who don’t want to follow to the other one, the short-answer to my conundrum seemed to be this: "mesh density."

In other words, don’t let the simulation surface have “too many” vertices. It can, in fact, be quite sparse … and “adding more” doesn’t make the simulation better. It seem to only make it slower, up until the point where it “explodes” (probably due to calculations of “the cloth colliding with itself”). Therefore, stay well away from that point.

To make the resulting cloth appear smooth and supple, add an appropriate smoothing modifier below it on the modifier stack.

(No, none of this advice is “new.” It just took me a while to grok onto it.)