# Description

Resolves Issue #1534 by adding non-root body tracking as an option in
the ViewerCfg. See the issue for justification/discussion. API as
follows:

- Adds origin_type "asset_body"
- Adds field "body_name"

When origin_type = "asset_body" and "body_name" matches a body in the
asset specified in "asset_name", the viewport is configured to track the
link frame of the body in world coordinates. By using the existing eye
and lookat fields in ViewerCfg the additional features are enabled:

- Tracking the end effector of an arm during manipulation (see below)
- Tracking a fixed offset from the end effector of an arm (e.g.
mimicking the view of a wrist-mounted camera)
- Tracking a mobile base using the currently-supported workaround for
lack of wheel physics by defining a virtual arm to mimic the motion of
the robot

## Type of change

- New feature (non-breaking change which adds functionality)

## Training Video from "Isaac-Lift-Cube-Franka-v0" after 1000
iterations.

Viewer defined as follows:

viewer = ViewerCfg(eye=(0.5, 0.5, 0.0), origin_type="asset_body",
env_index=0, asset_name="robot", body_name="panda_hand")

No other changes were made from the default environment definition.


https://github.com/user-attachments/assets/fff24b50-c9d0-48dd-b4c2-3641a11f0d4d

## Checklist

- [X] I have run the [`pre-commit` checks](https://pre-commit.com/) with
`./isaaclab.sh --format`
- [ ] I have made corresponding changes to the documentation
- [X] My changes generate no new warnings
- [ ] I have added tests that prove my fix is effective or that my
feature works
- [X] 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: Kelly Guo <kellyg@nvidia.com>
Signed-off-by: Kelly Guo <kellyguo123@hotmail.com>
Co-authored-by: Kelly Guo <kellyg@nvidia.com>
Co-authored-by: Kelly Guo <kellyguo123@hotmail.com>