Underwater cloth

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  02 February 2011
Underwater cloth

Hey everyone, I was hoping someone would be able to help me with a simulation I am trying to do. I need to create a digital character, wearing a roman tunic swimming underwater.

Having always used 3DS max, the cloth simulations are just not up to standard, so decided to switch to Maya and use nCloth instead.

As a complete Maya noob, I've only had minor success, which has just come from playing around within the nucleus, but just wondering if anyone could advise me, or knows a better way of simulating an underwater environment dynamic to ncloth, be it through nucleus settings, or some other way such as creating a fluids field.

Any help or advice would be greatly appreciated, thanks all!
  02 February 2011
For underwater cloth, I would suggest increasing the air resistance and the weight of the cloth, while reducing gravity.
  02 February 2011
You're not the only one who turns to Maya for the sake of cloth simulation. Apart from the nucleus settings, you may want to construct a better garment with something like jc.clothes 2 .
  03 March 2011
The key with underwater cloth is that the mass of water is greater than air, so one can simply increase the airDensity attribute on the nucleus node. Also if the cloth is somewhat buoyant, then lowering gravity a bit might help. Don't increase the mass of the cloth, as this will counteract the effect of increasing the air density.

Instead of increasing air density on the nucleus node you could also increase drag on the cloth( some tangential drag is also a good idea, but set lift to zero or a low value ).

If you wanted to get fancy and simulate bubbles of air trapped in the clothing you could emit colliding liquid nParticles with "ignore gravity" and an upward directional field applied. (make the system intermediate object so it doesn't render).


Last edited by Duncan : 03 March 2011 at 07:45 PM.
  03 March 2011
Thanks for the responses guys I've put them into effect and starting to make better progress!

To illustrate what I'm really looking for, if anyone is able to advise me further, this was some test footage we shot in a local diving pool (apologies for the low quality)

Underwater test footage

The movments of the tunic here are exactly what I am trying to replicate in nCloth. This is my first test render to show where I am so far, but as you can see it's not quite on the mark yet

nCloth test render

So if anybody could give further advice, aside from that already given above, to replicate this as closely as possible, it would really be greatly appriciated!
  03 March 2011
You might try a little more drag, but keep tangential drag very low, but non-zero.
Another possiblity is to apply the underlying object motion as a force on the cloth. There are different ways of doing this. One ways to constraint the cloth to the surface of the character and use motion drag on the constraint but with zero constraint strength/tangentStrength. Avoid using input mesh attract ( or at least keep levels low or just paint the strength in certain areas) as it can result in a stiff motion. The motion drag allows the cloth to move to any position, but pulls it with the relative motion of the surface( rather that attracting to the absolute position). This can help simulation the suction along the back as one moves forward.

You could also add a little animated turbulence force to simulate swirling water eddies. The turbulence on volume axis fields is useful for this.

  03 March 2011
awesome Duncan.
  03 March 2011
Thank you very much Duncan, it's greatly appreciated! I'll put your advice into effect and see how I get on from there!
  03 March 2011
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