I'm trying to simulate a soft contact using DART. I created one box object and added <soft_contact> tag in its sdf file. Then I place another mass on that box. I thought there could be different deformation(a sinkage?) on that box with different stiffness setting, but that mass stays on the surface of the box no matter what value I set. I tried a stiffness value from 100 to 0.01. The mass doesn't sink in and stays as shown in pic.
BTW, it seems adding force on an object in DART doesn't work either.