Disable sim sensors when using the batch renderer.

[0mdc]

Motivation and Context

This change prevents the simulators to allocate sensor memory and render them when using the batch renderer.

How Has This Been Tested

Tested locally from habitat-lab.

Types of changes

• Bug fix (non-breaking change which fixes an issue)

Checklist

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have read the CONTRIBUTING document.
• I have completed my CLA (see CONTRIBUTING)
• I have added tests to cover my changes.
• All new and existing tests passed.

[eundersander]

I left some comments. Have a look and try to address, but basically LGTM.

[eundersander]

Can you explain what's going on here? How can we safely call get_observation if we haven't rendered here? Is this relying on some external code to have already triggered rendering?

[0mdc]

When batch rendering, get_observation() returns None, creating an empty "placeholder" for this sensor uuid. The batch renderer replaces this value by the rendered data in post_step().

This is a bit of a hack as Habitat-Lab has checks to make sure that all sensors are present in observations between reset()/step() and post_step().

An alternative would be to skip those checks for visual sensors when batch renderer is activated, but I'm afraid that this is more confusing.

I admit that the behavior could be clearer here.