[SOLVED] Unit of Young Modulus in TetrahedronFEMForceField and SurfacePressureConstraint

Hi Sofa community,

I am super confused of the unit of Young Modulus in FEMForceField. I didn’t find any explicit introduction in the documentation. After searched online, I found two contradicting sources of it.
The first information from the forum indicated that the unit of Young Modulus relied on the one of length. Meter corresponds to Pascal while millimeter works with MegaPascal.

I found another version in the archive of emails. It claimed that the unit was always Pascal.

I think the second source is making more sense, because the young modulus in the pneumatic finger example from SoftRobot Plugin, is 400 MPa, based on the unit in millimeter of length. However, it exceeds the range of regular silicone rubbers. Also, when I tried my hands-on rubber with around 2MPa, the simulation broken down with 0.01 in surfacePressue.

Can anyone help me decide the correct units? Also, I am struggling in understanding the units of SurfacePressureConstraint from SoftRobot Plugin as well. Can anybody help with that?

Thanks,
Zhichao