[SOLVED] Using "FreeMotionAnimationLoop" is stopping "TetrahedronFEMForceField"

[Noura]

Hello,

I noticed that using the FreeMotionAnimationLoop will stop the ‘TetrahedronFEMForceField’ component from working.

A quick example to illustrate this is the famous tutorial scene “TutorialForceFieldLiverFEM.scn” in (/src/examples/Tutorials/ForceFields)
It is sufficient to include <FreeMotionAnimationLoop/> in the main scene node to notice that the liver is not deforming anymore!

As far as I know, the “DefaultAnimationLoop” is set by default in any simulation when no other animation loop is set explicitly. However, I have to use the FreeMotionAnimationLoop because I’m using BilateralInteractionConstraint which in turn require it.

I’m wondering if someone has faced the same issue before?

Thanks,

Noura

[Hugo]

Hi @noura,

This is not a bug, but due to the resolution process implied with the FreeMotionAnimationLoop. As you can notice from the Lagrange constraint documentation, a specific ordering is required in the resolution:

• first the free motion will be computed
• but if no ConstraintSolver and a ConstraintCorrection are detected, the correction needed can not be computed, and the update of the DOFs won’t be done, i.e. the object won’t move nor deform.

I hope this helps.
Best,

Hugo

[Noura]

Hi Hugo,

Yes, that’s true. I forgot to include a ConstraintCorrection in the deformed object node. Now it works fine.

Thanks for the quick hint!

Noura

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