Eliminate SimCloth Jitter

[Tom]

[Mod Edit: this discussion from Live Answer Time is now split into its own topic]

Might have a topic for today. How to stop "jiggling" cloth????

JiggleTest.prj

[Madfox]

I was just trying the same sim_cloth procedure on a model''s hair. For what I learned is that when you make the time count for the sim_cloth as long as it falls, it will stop on that moment with glitching. 

You could take a look at the choreography in the model spline mode and see this trembling in the splines. When deleting all spline tremble behind the point of fall down it will stay paralysed. 

My failure is that the sim_cloth used on the hair acts much to harsh against the force I placed. So I took all spline tremblence and nihiliate the extra debris by shorten the height value. Then, by correcting the null point back to the middle, it looks like the hair is slowly trembling.

I know there must be a better way to fine tune the force emitter, but for now I haven' t had another solution.

Just finished a seventeen sec avi with it, but after five hours rendering the avi gets screwed. Some strange reaction of the video setting. 

[Madfox]

I have no participation in the saturday evenings questions, but the easiest way to do it would be to pick up the simcloth_splines after the last movement has took place, and then delete all the spllne movement. You select the test.mdl and then go in muscle mode. It can take some time before the splines get selected. I use AM17.0.

JiggleTest0.prj

after 1sec 10. Then the jigling stops. 

[robcat2075]

From our Live Answer Time discussion...

There are several properties we can modify to reduce or eliminate the lively jitter that default cloth settings produce.

• Damping
• Precision
• Sub Steps

Other possibilities are

• Patch Density
• Motion curve editing
• Attach groups

Damping

Your first gambit should be Damping. Damping is the internal resistance of the cloth to continued motion. There are two damping settings in the cloth properties.

Stretch/Shear is the deformation of the cloth, both along the spine and diagonally across the square patches.

A:M Help:
 

Quote

 

[Stretch Shear Damping is] the resistance of each spring to velocity difference of the two ends of the spring. Lower values will make cloth more "springy" and oscillating. Higher values will reduce oscillation.

Visible: Sometimes, Default: 0.1, Min: 0

 

Bend Angle is the curving of the splines along their length

 

This video shows a test model with default cloth settings, Bend Angle set to 20x the default, Stretch/Shear set to 20x and then both set to 20x.

(I suggest you view these videos fullscreen)

 The examples with increased damping come to rest more naturally.

 

The Chor has SimCloth properties also, including Sub Steps and Solver Precision.

 

Sub Steps is how many slices the time of the frame is initially divided into (Adaptive Subdivisions is how may times Sub Steps can be doubled if the process needs more divisions to solve the motion)

A:M Help:
 

Quote

 

SimCloth divides a single frame in a number of intervals and computes the cloth position for each of these substeps. More substeps mean a more precise result.

Default: 4, Min: 1, Max: 1000

 

 

This clip show the same model with the previous cloth material settings but Chor Sub Steps is set to 64 instead of 8:

The Default cloth, with less damping, takes a bit longer than the others to stop moving but with 64 Sub steps the random bubbling motion is gone.

 

Solver precision controls how finely the motion is calculated

A:M Help:

Quote

Controls the target precision for the non-linear conjugate gradient solver. Lower values mean a more precise, but slower, simulation. Values lower than 1.0 are preferable.

Default: 0.01, Min: 0

 

This clip again shows the models with the previous cloth material settings but Chor Solver Precision is set to 0.001 instead of 0.01:

The Default cloth retains some minor bubbling. If the Precision were refined to 0.0001 it would probably become insignificant.

 

Density

Denser cloth meshes aren't less likely to jitter but because the patches are smaller the jitter appears less. Denser meshes are often preferred for realistically draping cloth effects anyway.

This clip shows cloth with Chor defaults but with 3cm patches instead of 9cm patches

 

Editing motion CPs

In a post above Rien Brouwers ( @Madfox) suggests deleting the motion curve CPs after the cloth no longer needs to move. This is a technique I have often used and eliminates unneeded data in the saved PRJs.

Attach Groups

A Cloth Attach Group can be defined and turned ON to solidly immobilize any or all of a Cloth mesh for as long as the Group is ON. Attach Groups are discussed elsewhere on this forum and in a Hash Tech Talk I recall.

Summary: Increased damping values in the Cloth Material properties makes for more realistic cloth settling and less random bubbling. Altering other parameters may be useful also.

 

@Tom @Madfox @ChuckGram @Roger

[Tom]

very good...