[feature request] custom transformation of observation space

Hello,

I often need to manually transform the observation space shape and associated observations in order to match custom policies I’m using. Would it be interesting to add a pre-processing mechanism that would:

• customize the shape of the input. For now the shape is fixed like in (Box space): https://github.com/hill-a/stable-baselines/blob/a0b35d1f87046802baadbcbed59d3619a5f9bd92/stable_baselines/common/input.py#L25 I guess there are other places where this needs to be adapted
• transform the observation to fit in the desired shape. An example of that would be:

def transform(obs):
    return np.reshape(obs, ...)

I guess there would be at least 2 options to expose a custom transformer: add it as a parameter to the algorithm, or register it (2nd option preferred I think).

[antoine-galataud]

@hill-a thanks. I was about to write my own 😃

[hill-a]

I’m not sure I understand what you mean.

If you want to change the observation shape from the environment, you can use a custom environment wrapper that can transform your observation before it is used by the model.

If you want to change the way the batch shapes are handled, I wouldn’t mind an example, as I’m not sure how this could be used.

Or do you mean something else?