Hello, I would like to ask if its possible to model Gripper with two geometries having same joint which moves each geometry in opposite direction. Imagine thumb and index finger when grasping pen or some object. I would like to control them by one joint. Eg. if one have position of 50-deg other should have -50-deg, if first have 45 other is supposed to have -45-deg. My main problem is with joint behaving in the way I described. Is it possible to model? Thank you.
Yes, this is doable. Create the two joints as if they are independent. Then add an equality constraint saying that the two joint displacements must equal each other. This will be enforced softly, like all other constraints in MuJoCo. But you can make it hard enough by adjusting the solref and solimp parameters of the equality constraint.