Description

The observation manager has a couple issues when providing history_length != None. In particular:

1. The env.observation_shape is computed incorrectly for these groups when flatten_history_dim=False. (See below for a concrete example).
2. When flatten_history_dim=True the observation is not returned in a way that is easy to reshape to recover the common history dimension.

While 2 may be a feature request (I thought this was the expected behavior, but realized it is unclear in hindsight), 1 is certainly a bug with how the observations are being handled currently.

Steps to Reproduce

1. Create an observation group with multiple history-enabled terms. For example:

@configclass
class ObservationManagerCfg:
    @configclass
    class PolicyCfg(ObservationGroupCfg):
        history_length = H
        flatten_history_dim = False
        term1 = ObservationTermCfg(func=f1) # f1 returns shape (D1,)
        term2 = ObservationTermCfg(func=f2) # f2 returns shape (D2,)

    policy = PolicyCfg()

Expected: Upon instantiating the env, env.observation_space["policy"].shape is (num_envs, H, D1 + D2).
Actual: Upon instantiating the env, env.observation_space["policy"].shape is (num_envs, 2H, D1 + D2).

2. Create an observation group with flatten_history_dim=True (e.g., change this parameter of the last example.

When reading an observation from the observation manager,

policy_obs = observation_manager.compute()["policy"]

Expected: policy_obs.reshape(-1, H, D1 + D2) = torch.concatenate([term1, term2], dim=-1). Note this is poor syntax - but ideally we could reconstruct the observations with a coherent history dim.
Actual: policy_obs = torch.concatenate([term1.reshape(num_envs, -1), term2.reshape(num_envs, -1)], dim=-1). The reshape does not preserve a history dimension.

System Info

Describe the characteristic of your environment:

• Commit: f1a4975
• Isaac Sim Version: 4.5.0
• OS: Ubuntu 22.04
• GPU: RTX 5000 Ada
• CUDA: 12.2
• GPU Driver: 535.183.01

Additional context

Will open a PR with suggested changes to fix these issues.

Checklist

• I have checked that there is no similar issue in the repo (required)
• I have checked that the issue is not in running Isaac Sim itself and is related to the repo

Acceptance Criteria

• Concatenated, unflattened histories have the correct shape in env.observation_space
• History observations can be reshaped easily to preserve a history dim.