Cloth vertices go haywire when closing seams

[tonyinseattle]

I find that if I play with a cloth simulation too much -- ie stopping, re-starting, making a group to pull back a corner, etc. -- eventually the whole thing becomes corrupt and there's no choice but to start over. Like really start over -- dump the file and start over. Here's an example:

I made this circus tent model. I modeled the panels, used Garment Maker to arrange them, created seams, closed them and ran a 50-frame simulation without a hitch. Then I decided to pull back a corner of the tent opening. So I created a group and used Node to connect it to a Point, which I animated starting at frame 51. Nope, wouldn't work. Fabric became over-stretched. I slowed the animation down. Nope. So I removed it and decided to just let the animation run from it's last stopping point at frame 50 without changes. Nope... I can't get it to work again. 

So I erased the entirely simulation to start over. Won't work anymore, even though the settings were the same. I tried more subsamples and fewer. Tried different mesh densities. No matter what, it won't run.

So I Reset State. Now, using the sewing springs, I tried to re-close the the seams. Now that's haywire, too. The seams won't close and the vertices are scattering every which way. It's like the whole model is corrupt. See photo.

I'm attaching this file for you. I left it in the state in the photo. To try this yourself:

1. In the cloth modifier, Reset State

2. Click Simulate Local (damped) and watch it go crazy.

Do any other settings look off? The simulation ran with these settings before. Why won't it run again? Has anyone else experienced this strange behavior in cloth? Once it decides to stop working, it won't work no matter how far back in the process you go.

[tonyinseattle]

I should add that I'm using 3ds Max 2019 -- the absolute latest version. 

[Anonymous]

Seems to work here:

• Reset state
• Simulate local (damped) until seams closed
• Set initial state
• Created and animated helper used as node-group.
• Simulated (Subsample:5)

[tonyinseattle]

Hmmm.... So, I downloaded the file that I uploaded here (to make sure I had the absolute right one), hit Reset State, then Simulate Local (damped) and it worked.

And I guess, this is my point. Somehow cloth seems to get corrupted the more you use it or the longer you have the file open. In other words, a simulation that worked previously won't work anymore *even with precisely all the same settings.* This persists even if I open or close the file, restart my machine. Something about uploading this file to the Forum, and then downloading it back to my machine made it work again.

Also, yesterday after posting, I downloaded Max 2020 and opened the file there and it worked. So I continued working, only to find that the simulation eventually failed there, too -- without a change in settings.

So, is there memory storage or a cache somewhere associated with a cloth simulation that gets corrupted, or can anyone explain how this might be happening?

[tonyinseattle]

One final question: After you his Simulate Local (damped) to get the seams close together, don't you have to stop the damped simulation, then uncheck Use Sewing Springs, and then restart the damped simulation to bring the seams all the way together? I noticed you have big creases in your simulation where the fabric should be somewhat smooth. Even though the first damped simulation works for me now, the second one messes up some of the seams for me.

[Anonymous]

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@tonyinseattle wrote:

One final question: After you his Simulate Local (damped) to get the seams close together, don't you have to stop the damped simulation, then uncheck Use Sewing Springs, and then restart the damped simulation to bring the seams all the way together? I noticed you have big creases in your simulation where the fabric should be somewhat smooth. Even though the first damped simulation works for me now, the second one messes up some of the seams for me.

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How would the panels hold together if you remove the sewing springs? If the seams bother you, put an Vertex weld on top after the cloth modifier.

Or even better: Scrap that Garment Maker all together and model a continuously mesh as tent cloth and simulate that.

[Anonymous · Accepted solution]

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@tonyinseattle wrote:

Hmmm.... So, I downloaded the file that I uploaded here (to make sure I had the absolute right one), hit Reset State, then Simulate Local (damped) and it worked.

And I guess, this is my point. Somehow cloth seems to get corrupted the more you use it or the longer you have the file open. In other words, a simulation that worked previously won't work anymore *even with precisely all the same settings.* This persists even if I open or close the file, restart my machine. Something about uploading this file to the Forum, and then downloading it back to my machine made it work again.

Also, yesterday after posting, I downloaded Max 2020 and opened the file there and it worked. So I continued working, only to find that the simulation eventually failed there, too -- without a change in settings.

So, is there memory storage or a cache somewhere associated with a cloth simulation that gets corrupted, or

can anyone explain how this might be happening?

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Honestly, i blame Garment Maker. I never was a fan of this, seems like a complete waste of time tinkering with it around. I always did my cloth by modeling with standard polymodeling techniques and got stable simulations, even with complex multi-layer clothing.

[tonyinseattle]

Might be. I did collapse the stack below the cloth modifier to see if that made a difference, but it did not. Of course, the geometry might’ve been flawed due to Garment Maker. I think I’ll try rebuilding from scratch without garment maker to see how that goes.

[tonyinseattle]

My understanding is that having Use Sewing Springs checked while running the damped simulation brings the fabric closer together but never actually seams them. If you zoom in you’ll see a tiny gap. You have to uncheck Use Sewing Springs and then run the damped simulation again to bring them all the way together. 

See this Autodesk tutorial:

https://knowledge.autodesk.com/support/3ds-max/getting-started/caas/CloudHelp/cloudhelp/2018/ENU/3DS...

To find the relevant section, find this text on the page:

Fit the pullover to the model’s torso:

Thanks,

Tony

[tonyinseattle]

You are absolutely right. I got rid of Garment Maker and built everything from scratch (which took more time) but the simulation ran smoothly after that.

It's really a shame that Autodesk seems to have completely forgotten about this area of Max. It really does not work well at all. And I can't remember the last time it was updated.