nCloth simulation timing

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Old 03 March 2007   #1
nCloth simulation timing

Hi all,

I have a little problem with nCloth simulations timing. When I render (tga's sequence) a simulation, and then I play it at 25fps, it moves really slow, so I have to increase the fps a lot (around 90fps to see it 'natural').
The items I'm using are not bigger than 100cm, I've tried with different working units (cm, meters, etc...), and playback speed is set at 'Play every frame'.
So, I guess I'm missing something but I'm not sure what it is. Sorry if this is a very stupid question, but I don't have much experience with Maya.

Here are two examples of what I'm talking about:

At 25fps (really slow). Mov file. 1.1Mb
At 90fps (better) Mov file. 1.1Mb

Jacobo Barreiro | CG Artist | ILM |
Old 03 March 2007   #2
Looks like you need to adjust your Scale Attributes on the Nucleus Solver

Time Scale

Determines the relative time nCloth is running with respect to the Dependency Graph time. For example, if you want the cloth to run through the simulation twice as fast, the Time Scale value should be set to 2. The longer the nCloth's simulation time is, the more force has an effect on the Cloth. For example, if the force is gravity, the nCloth will appear to be heavier as the Time Scale increases. The default value is 1.

Space Scale

Determines the relative space scale applied to this Maya Nucleus solver. The Maya Nucleus solver treats nCloth objects as a scale model and applies the specified forces internally to get the expected behavior for the actual nCloth object at its actual size. The default value is 1.

Gravity interprets Maya’s units as meters. When the working units of your nCloth’s scene is not set to meters (such as Maya’s default centimeter working unit), you may need to adjust the Space Scale of your nCloth’s Maya Nucleus solver. Otherwise, the large-sized nCloth objects in your scene may not behave as desired. For example, when Space Scale is 1.0 (default), Gravity treats a 100 centimeter wide nCloth object like it is 100 meters wide. To improve the behavior of your large-sized nCloth objects, reduce the Space Scale value.

If you are modeling such that one unit is equal to one centimeter, the Space Scale value should be set to 0.01.

Last edited by Aikiman : 03 March 2007 at 09:46 PM.
Old 03 March 2007   #3
Thank you so much for your response and help. That seemed to be exactly the problem. I've adjusted the time and space scale a lilttle bit, and it runs perfect!

Thanks again!
Jacobo Barreiro | CG Artist | ILM |
Old 03 March 2007   #4
Avoid using the timeScale on nCloth for now. There is a bug where moving passive objects will not collide correctly if the timeScale is not exactly 1. The spaceScale is fine however. Note that gravity is the primary driver of this animation, so that the intensity of gravity will generally affect the overall speed. SpaceScale for the most part just adjusts gravity.

Old 03 March 2007   #5
Thanks for the advice, Duncan. I'll take that into account.
Jacobo Barreiro | CG Artist | ILM |
Old 04 April 2007   #6
Hi again!

I got a question about nCloth, and exporting geometry. I'm trying to get one frame of the whole deformation, and set it as initial state. So far so good. But then I want to remove nCloth and keep that deformation in the geometry permanetly, to export it as an object (OBJ, or so).
Is there any way to freeze? I'm sure there is, but I wasn't lucky looking for help in the manual...
Jacobo Barreiro | CG Artist | ILM |
Old 04 April 2007   #7
Set initial state sets an array attribute on the cloth node, which thus won't help you.

Instead simply delete all the nodes that are upstream(to the left in hypergraph:connections) of outputCloth mesh. The output cloth mesh is then the mesh you export.

Old 04 April 2007   #8
Just perfect!! Exactly what I needed!
Thanks a lot for your help Duncan!
Jacobo Barreiro | CG Artist | ILM |
Old 04 April 2007   #9
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