How to turn off damping for TetModel

[Theodotus1243]

Hi @janbender
I've set gravity = [0, 0, 0] and initialized addRegularTetModel with addSolidConstraints
Then I've spinned it to 200Hz, but for some reason after 2 seconds angular velocity reduced a lot

I thought it had to do with some kind of friction. But setFrictionCoeff(0) and setRestitutionCoeff(1) did not help.
Also I've found sim.setDamping(0.001f); but it's only related PositionBasedElasticRodsDemo.cpp

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I think it's related to DamperJoint from which the object is created. But I haven't found how to zero damping coef

[Theodotus1243]

Actually there is no problem if I need to add some Joints between vertices The question is do all the Joints have damping and where it comes in Tet variant

[janbender]

Which method did you choose in the call of addSolidConstraints? Friction and restitution only applies to collisions. So if there are no collisions, this won't change anything.

Note that PBD suffers from numerical damping (similar to the implicit Euler integrator). You can improve this by using the second-order velocity update. Otherwise you can test if it gets better when reducing the time step size.

[Theodotus1243]

Thank You very much
I was using simMethod = 3, but tried 1-6 too, paying more attention at 1,3,6, no principal difference. I've looked and them and saw that simMethod = 1 is just distance and volume constraint with no explicit damping, so thought that it's numerical damping

Time step reduction in 10-100 times looks like further accererates damping. Making object bigger slows down damping
(Not sure about this two statements, but those changes don't help much)

Hoping a lot on second-order velocity update

[Theodotus1243]

@janbender Thanks
I've set

ts = sim.getTimeStep()
ts.setValueInt(
    pbd.TimeStepController.VELOCITY_UPDATE_METHOD, 
    pbd.TimeStepController.ENUM_VUPDATE_SECOND_ORDER
)

And it's looks much better
The issue lookes resolved for now