Elastic Foundation Force Computation Error about simbody HOT 3 OPEN

Thank you for the detailed report!

Once concern I have is that OpenSim is still using the deprecated ElasticFoundationForce element, rather than the preferred implementation as a ContactForceGenerator (see CompliantContactSubsystem.cpp:1824 for the force calculation). Likely that has similar behavior though -- can you tell by looking at the code?

The Elastic Foundation model has many limitations -- ignoring face normals is one, and inability to deal with fully-buried objects is another. Usually the cure is to make a denser mesh, and to avoid simulations in which objects become embedded in one another. Are those feasible in your case?

cc @aymanhab

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BTW although Simbody's ElasticFoundation models require fairly dense meshes to give reasonable behavior, we have recently developed a new method ("Pressure Field Contact") which is far better and gives smooth forces for any mesh, however coarse. Here is the published and arXiv versions of a paper describing it.

The only implementation of that I currently know of is in Drake, but it would be a great addition to Simbody and OpenSim if anyone is interested in tackling that.

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Thank you for your quick response. I really appreciate you taking the time to help me. I will look into the preferred implementation for the force computation and see if I can refine my mesh to obtain more accurate results. I will keep you updated with any progress. Thank you again for all your help.

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