Function get_parallel_joint_torque 

pub fn get_parallel_joint_torque(inv_h: f32, base: &mut JointSim) -> Vec3

(b3GetParallelJointTorque)

C takes (b3World* world, b3JointSim* base); the port only needs world->inv_h, taken by value so callers that already hold base as a mutable borrow of world (e.g. a future joint-type dispatcher) don’t hit a double-borrow of world.