[SOLVED] How should i use damping in HexahedronFEMForceField

[ruiliang]

Hi all,

I have modeled a thickcurve using hexahedron mesh. When i cut it, it drops down by gravity and keep swinging up and down. I think this comes from the damping parameter doesn’t work in HexahedronFEMForceField.(I have rayleigh stiffness = 0.1 for the curve but it still swings too much)

I went through some SOFA examples and i only saw ‘DiagonalVelocityDampingForceField’. Is there a way to achieve damping effects in HexahedronFEMForceField? (like by setting ‘dampingCoefficient’ in DiagonalVelocityDampingForceField). Or is there any other way to solve my “thick curve swinging”problem?

Thanks in advance!

[Hugo]

Hey Ruilang,

Not sure to understand, when you cut there’s still a point attached?

About damping, Rayleigh damping is a numerical damping, usually used to stabilize or ease convergence of the simulation. But it has to be used with caution since it can strongly affect the solution of your system. You can also add your own damping or using the DiagonalVelocityDampingForceField (I never used it myself).
But more generally, I am not sure that damping would help in your problem.

A video illustrating your issue would help the understanding.
Best,

Hugo

[ruiliang]

Thanks Hugo,

I have found out that DiagonalVelocityDampingForceField is exactly what i need. By adding this component to my hex-curve, the issue has been fixed and the model behavior is quite realistic!

The issue i had is that after the curve being cut, one end is attached to another object and the other end drops down by gravity. Then it keeps swinging up and down since it is pure elastic behavior without damping.(Rayleigh damping works but it affects the stretchability behavior too much so i don’t want to increase it).

[Hugo]

Very nice to hear !!!

Indeed, damping is dedicated to this purpose: damping a system that oscillates.
Thank you for explaining the whole story !
Keep us updated !

Cheers

Hugo

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