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View Full Version : Unwanted rotation or movement after ncloth inflation


berniebernie
07-16-2009, 09:21 AM
Hello fellow cgtalkers

The title says it all:

With gravity removed from the nucleus; I pump pressure into a ncloth object, yet without any constraints or fields, the object drifts away, has some rotation to it. I'd like the shape to stay put.

http://mlkdesign.online.fr/dump/ncloth_help.gif

It is a perfectly symmetrical mesh. I've tried nconstraints to no luck

Any help ?


Than you, and have a good day.

HowardM
07-16-2009, 09:48 AM
turn down/off your Lift setting.... could also turn up Damp, Drag, etc...

berniebernie
07-16-2009, 01:14 PM
thank you... that and nconstraints worked


edit: hefty work shown on your website, impressive!

Duncan
07-16-2009, 08:23 PM
The solver normally does stretch evaluation sequentially which creates stronger stretch resistance for a given number of iterations, but results in a bias(that causes this drift because the stretch fights against the pressure). You can avoid this by making the nCloth evaluation order "Parallel". It will then be more stretchy and you will need less pressure to inflate( or need to pump in less air ) and also should no longer drift. You can imagine that a cloth balloon made out of something like nylon or silk would require tremendous air pressure to make it stretch and expand( the stretch resistance of rubber would be much lower ). In generally it is easier for the simulation( if you want to blow up a balloon ) to keep the cloth stretchy (low stretch resistance value). However note also that technically the default values for stretch resistance and pressure incompressibility are quite low... more like balloon rubber and a very thin gas. But as long as the relative difference is the same then keeping them low will allow you to simulate with fewer iterations and substeps( faster ).

Duncan

Als
07-21-2009, 09:50 AM
Try to use instead of poly sphere, subds sphere, convert to polygons.
This will have more even spread of points, so more even forces too...
Compare and you will see what I mean...

Als

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