mj_jac() and related functions provide a geometric ("end-effector") jacobian. The result is (3 x nv) and could be used as: (Where v is qvel and q is qpos) I.e. to calculate some end-effector velocity based on joint velocity. However, for my current application I need a jacobian for qpos. (For a model with quaternions, so it is not easily related to qvel). I specifically need the jacobian according to the classic definition: Is there way to find this position geometric jacobian instead of the velocity geometric jacobian?