Hi, My question is about mujoco-py so I understand it may not be able to be answered here but perhaps I can have some guidance about approaches to explore. I would like to take the state of simulation and change another simulation to that state so I can simulate forward in time without taking a step in the first environment. I've seen this question, this question, this question, and this question. It seems like I need to edit the qpos and qvel but I don't think that everything I need is stored in those two. The environment I'm using has 2 categories of state and 1 model parameter I would like to change: 1. Position and velocities of robot joints 2. Position and velocity of robot center 3. Position of objects in scene (these are static) I believe that 1. is stored in qpos and qvel and I have changed that successfully by calling ``` self.sim.set_state(other_sim.sim.get_state()) ``` to change 2. and 3. I edit the data directly ``` self.data.body_xpos.flags.writeable = True self.data.body_xquat.flags.writeable = True self.data.body_xmat.flags.writeable = True self.data.body_xvelp.flags.writeable = True self.data.body_xvelr.flags.writeable = True self.data.geom_xpos.flags.writeable = True self.data.geom_xmat.flags.writeable = True self.data.geom_xvelp.flags.writeable = True self.data.geom_xvelr.flags.writeable = True self.data.body_xpos[0:] = state['body_xpos'] # copy of other simulation's body xpos etc. self.data.body_xquat[0:] = state['body_xquat'] self.data.body_xmat[0:] = state['body_xmat'] self.data.body_xvelp[0:] = state['body_xvelp'] self.data.body_xvelr[0:] = state['body_xvelr'] self.data.geom_xpos[0:] = state['geom_xpos'] self.data.geom_xmat[0:] = state['geom_xmat'] self.data.geom_xvelp[0:] = state['geom_xvelp'] self.data.geom_xvelr[0:] = state['geom_xvelr'] ``` and I edit the model ``` self.model.body_pos.flags.writeable = True self.model.body_quat.flags.writeable = True self.model.geom_pos.flags.writeable = True self.model.geom_quat.flags.writeable = True self.model.body_pos[0:] = state['body_pos'] self.model.body_quat[0:] = state['body_quat'] self.model.geom_pos[0:] = state['geom_pos'] self.model.geom_quat[0:] = state['geom_quat'] ``` and step forward the simulation: ``` self.model.compute_subtree() self.sim.forward() ``` this seems to successfully accomplish 1 and 3 but after testing sometimes after thousands of steps the robot position and velocity does not agree between the two simulations. Perhaps I am misunderstanding something but I would think I have set all the data necessary. I apologize for my ignorance, I am a beginner at robot simulation. My questions are: 1. Is there something else I need to set in order for both simulations to behave the same? 2. What does self.sim.forward() do?