# Description

Certain scene-level randomizations (such as randomizing the scale) must
happen before the simulation starts playing. To this end, the MR adds a
new event mode called "prestartup," which gets called right after the
scene design is complete and before the simulation is played.

Since the scene entities cannot be resolved before the simulation starts
playing (as we currently rely on PhysX to provide us with the joint/body
ordering), the MR adds a callback to resolve the scene entity
configurations separately once the simulation plays.

This MR replaces the prior implementation in #1165

## Type of change

- New feature (non-breaking change which adds functionality)
- This change requires a documentation update

## Screenshots

If you execute:

```bash
./isaaclab.sh -p scripts/tutorials/03_envs/create_cube_base_env.py --num_envs 32
```

Output:


![image](https://github.com/user-attachments/assets/a4b3a5e7-ff5c-4593-97ce-3b5af19bfde2)

## Checklist

- [x] I have run the [`pre-commit` checks](https://pre-commit.com/) with
`./isaaclab.sh --format`
- [x] I have made corresponding changes to the documentation
- [ ] My changes generate no new warnings
- [ ] I have added tests that prove my fix is effective or that my
feature works
- [ ] I have updated the changelog and the corresponding version in the
extension's `config/extension.toml` file
- [x] I have added my name to the `CONTRIBUTORS.md` or my name already
exists there

---------
Signed-off-by: Mayank Mittal <12863862+Mayankm96@users.noreply.github.com>
Co-authored-by: James Smith <142246516+jsmith-bdai@users.noreply.github.com>
Co-authored-by: Kelly Guo <kellyguo123@hotmail.com>