Does the action precede the observation?

[GuoPingPan]

I found that when collecting data, observation is the result after env.step(action). Does it mean that every pair in the dataset is (a_t, o_{t+1})? @zhuyifengzju

LIBERO/scripts/create_dataset.py

Line 177 in f78abd6

obs, reward, done, info = env.step(action)

   for j, action in enumerate(actions):

            obs, reward, done, info = env.step(action)

            if j < num_actions - 1:
                # ensure that the actions deterministically lead to the same recorded states
                state_playback = env.sim.get_state().flatten()
                # assert(np.all(np.equal(states[j + 1], state_playback)))
                err = np.linalg.norm(states[j + 1] - state_playback)

                if err > 0.01:
                    print(
                        f"[warning] playback diverged by {err:.2f} for ep {ep} at step {j}"
                    )

            # Skip recording because the force sensor is not stable in
            # the beginning
            if j < cap_index:
                continue

            valid_index.append(j)

            if not args.no_proprio:
                if "robot0_gripper_qpos" in obs:
                    gripper_states.append(obs["robot0_gripper_qpos"])

                joint_states.append(obs["robot0_joint_pos"])

                ee_states.append(
                    np.hstack(
                        (
                            obs["robot0_eef_pos"],
                            T.quat2axisangle(obs["robot0_eef_quat"]),
                        )
                    )
                )

            robot_states.append(env.get_robot_state_vector(obs))

            if args.use_camera_obs:

                if args.use_depth:
                    agentview_depths.append(obs["agentview_depth"])
                    eye_in_hand_depths.append(obs["robot0_eye_in_hand_depth"])

                agentview_images.append(obs["agentview_image"])
                eye_in_hand_images.append(obs["robot0_eye_in_hand_image"])
            else:
                env.render()