Help with cloth sim

[Naeem]

Hi,

I am trying to simulate a tent moving in the wind. The movement has to be very subtle. I can't quite figure out how to get a realistic wind simulation. Something that causes a slight ripple in the cloth and then the cloth goes back to its initial position - like flaps or curtains.

Attached is my hip file. Thanks.

od_ClothSim.hip

[GallenWolf]

One idea would be to just blend (Blend SOP) the simulated geo back to the initial position. Or if it's that subtle, skip the sims and just blend between various sculpted geometries of the cloth?

GW

[Guest tar]

For the rippling cloth you'll need more polygon detail. A good way is to use a proxy cloth. See if our flapping flag examples/discussions help. I think we got pretty close by the end.

http://www.sidefx.co...ewtopic&t=29032

Edit: added a test file

TentTest.hipnc

Edited July 4, 2013 by tar

[Naeem]

Thanks GallenWolf and Marty for the file.

I was thinking about blending between various sculpted geos but I wanted to give cloth a shot since I've never done any cloth work before and I want to learn. I'll see what I can achieve with cloth before I look at alternative ways of achieving the effect.

[JuriBryan]

just a idea, but it might work.

you can create a ocean with the waves representing the ripples of the cloth the way you want them to be, so as small and slow as you want.

That should give you a lot of control over the look.

Then you can export the velocity field of the ocean and rotate it like the cloth of your tent.

Now you feed the vel of the ocean in as field force and together with some pin constrains, rather tight cloth settings and some gravity you should get exactly what you want....

At least I am 90% sure that this should work:)

[Hudson]

I like Juri's idea! To add even more controll to his idea you could paint a velocity multiplier attribute before using it as a field force so you only get the deformation where you want it to be .

[old school]

I was thinking about blending between various sculpted geos but I wanted to give cloth a shot since I've never done any cloth work before and I want to learn. I'll see what I can achieve with cloth before I look at alternative ways of achieving the effect.

Another approach is to use the Cloth Solver Animated geometry input to add forces to your cloth.

The Cloth Object DOP has an input for animated geometry where you can impart a tug on your Animated geometry. That is insert SOPs before the Null SOP called TARGET in your cloth object that is referenced by the Cloth Object DOP's animated geometry parameter.

The cloth may not be able to get to your animated geometry position due to the cloth itself but the forces will be fed in to the solver and applied to your cloth object. You can also paint a target mask using the targetstiffness and targetdamping point attributes. You can flood 0 for these over the entire cloth and then paint up to 1 for those areas that you want to apply the forces to.

You could use this to add a ripple deformer to tug your cloth about based on how you want it to deform, to impart forces in to the cloth sim. If you want to direct this.

Of course you read the help card for the Cloth Object DOP which explains the Target geometry amongst other features and attributes. First place you go, right?

od_ClothSim_TARGET_jw.hipnc

Edited July 5, 2013 by old school

[Naeem]

@JuriBryan - Great idea! Will surely look into it!

@old school - Thanks! I've been reading the help and surely getting further with what I want to achieve. I read your answer in the thread http://www.sidefx.com/index.php?option=com_forum&Itemid=172&page=viewtopic&t=29032 and it's been massively helpful! Thanks for the file too.

[Naeem]

A quick question about something I am having difficulty understanding - is there an attribute on the cloth object that controls how fast a cloth is pulled back to it's initial position after it has been affected by a force/velocity?

Edit : I think damping does that? The basic idea is to create a flapping in the wind kind of motion. So if I have an external velocity offset set on the cloth object in the direction of the wind, I want it to behave in a way that the cloth gets pushed by the force and then pulled back in the direction of its initial or rest position.

Edited July 9, 2013 by Naeem