Add support for indirect light setting for env

[yuecideng]

Description

Add randomize_emission_light functor to support domain randomization of global emission light properties. This is a common technique for improving sim-to-real transfer in vision-based tasks.

The new functor samples emission light color (RGB) and intensity uniformly from configurable ranges and applies them globally via env.sim.set_emission_light. Unlike randomize_light which targets specific scene light objects, this controls the scene-wide emissive lighting.

Corresponding documentation has been added to the Visual Randomization functor table in docs/source/overview/gym/event_functors.md.

Fixes # (issue)

Type of change

• New feature (non-breaking change which adds functionality)
• Documentation update

Screenshots

N/A

Checklist

• I have run the black . command to format the code base.
• I have made corresponding changes to the documentation
• I have added tests that prove my fix is effective or that my feature works
• Dependencies have been updated, if applicable.

[Copilot]

Pull request overview

Adds support for configuring and domain-randomizing global emissive (“environment emission”) lighting, complementing the existing per-light-object randomize_light functor.

Changes:

• Add randomize_emission_light visual randomization functor that applies global emission light color/intensity via env.sim.set_emission_light.
• Extend env lighting config to accept an indirect section and apply emission_light during environment light setup.
• Document the new functor in the event functors table.

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 4 comments.

File	Description
embodichain/lab/gym/utils/gym_utils.py	Parses light.indirect from config into EmbodiedEnvCfg.
embodichain/lab/gym/envs/managers/randomization/visual.py	Adds randomize_emission_light functor and exports it.
embodichain/lab/gym/envs/embodied_env.py	Adds EnvLightCfg.indirect and applies emission_light in _setup_lights().
docs/source/overview/gym/event_functors.md	Documents randomize_emission_light in Visual Randomization table.

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