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Problems with cloth modifier. Sim fails under high movement speed.
show user profile  xcloudx
Hey, i'm having some problems with the cloth modifier and was wondering if you guys could maybe give some advice as to what i am doing wrong? This is the first time i have used it.

There is a part in my animation where my character suddenly jolts and moves at high speed and twists, my sim fails at this point and says "cloth has become over-stretched". Is there some way i can go about fixing this? I tried lowering the allowed stretch to something super low during these frames like 5 but it still will not complete the sim. On the last frames it managed to sim it seems to have exploded and gone weird in a few places.
Only way it seems i can get my sim to go further is i disable the underlying collision mesh, but then it wouldn't look right.
Do you guys have any ideas as to what i am doing wrong and how i can get it to work? Thanks
I'm still a bit unsure as to what all the different options do so i'm not really sure where the problem lies.

Here are the settings and how it looks when it fails. The collision meshs settings are the default depth 1 fric 0.1 static 0.5 and i changed offset 0.1

Edit: Got it working :), Turns out i needed to lower the collision meshs depth from 1 to 0.1 at the part where the sim fails. The cloth now in areas of high stress goes through the collision mesh slightly but next frame it fixes itself, rarther than flat out breaks the whole sim.
read 1863 times
1/25/2012 9:22:45 PM (last edit: 1/29/2012 3:11:48 PM)
show user profile  Nik Clark
Would upping the subsamples help?

read 1858 times
1/25/2012 9:25:06 PM (last edit: 1/25/2012 9:25:06 PM)
show user profile  xcloudx
I've tried going to 4 subsamples and 1 self collide subsample. still fails, should i go even higher?
read 1854 times
1/25/2012 9:25:55 PM (last edit: 1/25/2012 9:25:55 PM)
show user profile  Nik Clark
I am not great with cloth, but it seems to me that you might need to up those numbers, especially the subsamples, to avoid speed issues.

read 1851 times
1/25/2012 9:27:51 PM (last edit: 1/25/2012 9:27:51 PM)
show user profile  Mr_Stabby
yeap subsamples are what you need, i generally dont use a setting lower than 5 since it makes most fabrics behave unnaturally. for the jolt part you might need to bump it up as much 10x or even more (cant really say without knowing the animation) but you dont have to have the subsamples up that high the entire simulation, just simulate at low settings until you get to the tricky part, hit cancel, raise samples, get through it, cancel again, lower samples, continue

read 1843 times
1/25/2012 9:47:52 PM (last edit: 1/25/2012 9:47:52 PM)
show user profile  xcloudx
Alright thanks for the suggestion, still having some issues though but its better than it was.
Just tried upping the subsamples to huge amounts but i still can't get the sim to finish. But it got further this time with cleaner looking results.
I simmed it 50 samples but its still exploding at one frame then fails doing the next one. At least now its only one arm that is doing it rather than the entire shirt.
I tried 100 from a few frames prior but getting the same result.
Though during the sim it comes up a few times that the cloth-solid velocity was too large
read 1832 times
1/25/2012 11:57:38 PM (last edit: 1/26/2012 12:05:47 AM)
show user profile  killerbee2
try upping the samples more (try 20+) to and set self collision to 10.
If that fails as well, lower the static & self friction + increase the collision offset.

read 1822 times
1/26/2012 2:44:00 AM (last edit: 1/26/2012 2:44:00 AM)
show user profile  gogodr
from my experience
4 is too little.
7 is acceptable
14 is optimum
more is only if there are collision errors

Hello there

beautiful ;3

read 1818 times
1/26/2012 4:36:29 AM (last edit: 1/26/2012 4:36:41 AM)
show user profile  xcloudx
Still can't get it to complete the sim :(
With all the subsamples set really high, and friction set to 0 the collision mesh is coming through the cloth and then the sim fails on the next frame. Increasing the offset doesn't seem to have any effect on how far it gets.
read 1794 times
1/26/2012 7:37:26 PM (last edit: 1/26/2012 7:37:26 PM)
show user profile  Mr_Stabby
you can try upping collision object depth which can help if the tear occurs over 2+ frames

read 1782 times
1/26/2012 10:25:46 PM (last edit: 1/26/2012 10:25:46 PM)
show user profile  xcloudx
Ah still no luck with increasing the collision depth, doesn't seem to make a difference. :(
read 1759 times
1/27/2012 2:11:19 PM (last edit: 1/29/2012 2:54:02 PM)
show user profile  xcloudx
Hey just an update, I finally got it to sim!
Turns out the problem was that the collision depth was too high? Setting it to 0.1 at the problem frames made the sim complete, now instead of breaking the whole sim it just goes through the collision mesh slightly for one frame, then the next frame its fixed itself. I can then probably fix up that one frame with a relax modifier or something.

Its kind of weird though, i would of thought upping it would help, not lowering it? But the character also has these cloth packs that are attached to him and i use the other cloth sim as a collision mesh for it. Well when they touch together at high force the pack becomes stuck inside the collision mesh and wont come out, setting the depth higher just makes the collision mesh suck verts in like a vacuum and gets them stuck too, while setting it lower allows them to come back out next frame and work normally.

Thankyou for the help, also the cloth looks much better with your advice to up the samples. :)
read 1725 times
1/29/2012 3:00:22 PM (last edit: 1/29/2012 3:11:06 PM)
show user profile  Mr_Stabby
well it depends on the scale of the object, collision depth creates a sort of a volume shell inside the collision offset surface. In cloth sim if a vertex passes through the offset surface it enters this shell and the deeper it is the more force is given to it to push it out in the nearest path to the surface this are of the volume belongs to. Problem is though its a pretty blunt solution since if verts pass through the offset surface and go past the depth volume then its like the collision object was never there as far as they are concerned, if you set the depth too high though it comes though the other side of your object and starts pulling vertices into the object with great force while the volume area created on the other side is trying to push them out so they get stuck and go insane in general. To ensure no problems you have to make sure that a) the depth doesn't reach so deep that it would intersect the depth of the other side of the model b) that vertices never reach the max depth (more subsamples makes collision and expulsion more likely)

read 1702 times
1/29/2012 5:34:40 PM (last edit: 1/29/2012 5:34:40 PM)
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