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Underwater cloth 1 month 1 day ago #987

  • jnic
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Hi,
I need to run a simulation that would resemble cloth underwater on a translating and rotating character. I'm wondering if anyone would have any advice of what setting I could modify to try and get this behavior. For now I'm trying this with a standard flow node with no fields attached. Things I have tried so far:
- I've tried playing with the max linear motion to create a dragging affect however this slows it down but in a very linear way, I'm not getting any overlap on the rotating motion.
- I've tried using form drag but I'm find overall this seems to mostly dampen the cloth and also not give the overlapping motion I'm looking for

any pointers would be very well recieved
thanks
 

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Underwater cloth 1 month 1 day ago #988

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Hi,  I have shared your request with the team and we'll have more input in due course, but meanwhile did you try increasing the "air density" to create something like water density?  Txs, Mike

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Underwater cloth 1 month 23 hours ago #989

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Hi,
Thanks very much Mike for your reply very appreciated.
I had a look at the air density setting, I was trying to look within the documentation to find exactly how and what it affects within the solver but I wasn't able to so any additional information you would have on that would be great. For now the only test I did was google searching the density of water which came up as 997 which when I tried broke the simulation.

I had noticed on your blog posts you have an example of a very floaty dress/trousers from mocap doing a scissor kick which has a very nice overlapping/dragging motion on the cloth. I don't suppose you would still have the rough settings that were being used?

For now I'm continuing some tests on your example scene of the kenetic drive as it has a nice spinning motion that I can itterate on quickly. It's not as complex as the scene I'm working with in reality but still a good representation.

Once last additional question, in the cases where I do get a more floaty syle simulation I'm finding that as the character and collider tumbles the cloth can tend to become stuck to the collider. I also noticed in your v&a examples you have a character rolling on the floor where nothing seems to get stuck together and I was wondering if you would have any tips towards that too.

Thank you very much
James

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Underwater cloth 1 month 10 hours ago #991

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Hi James,
Feedback from the team was;

1) try using kinetic drive and aerodynamics (denser than air). But as you found already aerodynamics is not very stable because of the explicit nature of the forces and the kinetic drive seems to help with stability.

So option 2) Leave air density alone. Reduce gravity to say -0.5, adding a kinetic drive at 20%, adding a uniform vector field and playing with drag coefficients. Get the best results with the skin drag being bigger than the form drag. It is logical because skin drag is friction with the fluid while form drag is frontal resistance like car CX. Basically use form drag and lift the same and skin drag is double. You don't need to increase air density because you are tweaking form drag and lift.

>>I had noticed on your blog posts you have an example of a very floaty dress/trousers from mocap doing a scissor kick which has a very nice overlapping/dragging >>motion on the cloth. I don't suppose you would still have the rough settings that were being used?

don't have those settings to hand but will try and dig them out next week.

>>One last additional question... 
As this is a very common issue so I've added it as a tip of the week at this link - hope that helps.
forum.numerion-software.com/index.php/ti...oth-collision-issues

Cheers,
Mike

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