README.md

---
license: cc-by-nc-4.0
tags:
  - digital-twin
  - usd
  - isaac-sim
  - physics
  - lighting
pretty_name: Intelligent Home Care Living Lab (Digital Twin)
---

# Intelligent Home Care Living Lab — Digital Twin

A USD digital twin of the **Intelligent Home Care Living Lab** (alias: *NYCU Room 305*), built by the
**Human-centered Intelligent System Lab (hcislab)** — [GitHub @HCIS-Lab](https://github.com/HCIS-Lab).
Authored for **NVIDIA Isaac Sim 5.1**.

This is a **foundation twin**: it is the room only — **no furniture, no robot, no task props**. Every
project *references* it and layers its own content on top (a robot, furniture, graspables, sensors)
**without editing the twin**. That keeps one canonical, physics-ready room shared across projects.

**Lab links:** [GitHub @HCIS-Lab](https://github.com/HCIS-Lab) · [HF @hcislab](https://huggingface.co/hcislab)

## What's new (2026-07-04)

- **Physical properties are now set.** Every room surface is a static collider (exact triangle-mesh,
  `physics:approximation = "none"`) and the scene carries a `PhysicsScene` + a ground physics material
  (friction, no bounce). Robots and props now rest on / collide with the room instead of falling through.
- **Structured into layers.** The monolithic file is split into a visual layer, a collider layer, and a
  thin top composition — so you can reference exactly what you need (visual only, or visual + physics).

## Contents

```
room.usd                   # ← ENTRY POINT. Top composition: Z-up / meters / kg,
                           #   references the visual layer + sublayers the collider layer,
                           #   adds a PhysicsScene and the ceiling RectLight.
nycu_lights.usdz           # VISUAL layer — geometry (443 meshes, ~188k pts) + 417 materials
                           #   + bundled textures + DomeLight. No physics. Self-contained.
room_collider.usd          # COLLIDER layer — an overlay that adds CollisionAPI (approx=none)
                           #   to every room mesh + a ground physics material bound at /Room.
nycu_light_collider.usd    # COMPAT SHIM — the historic entry point; now just references
                           #   room.usd</Room>. Kept so existing pipelines don't break.
```

`room.usd` references `nycu_lights.usdz` and sub-layers `room_collider.usd` by **relative** paths, so all
files must stay side by side. `snapshot_download` keeps them together automatically.

Scene stats (Isaac Sim 5.1): 443 meshes (~188k points), 417 materials, a `DomeLight` + `RectLight`,
443 static mesh colliders. Approx extent 12.1 × 7.0 × 3.4 m.

## Usage

```python
from huggingface_hub import snapshot_download

path = snapshot_download(repo_id="hcislab/digital-twin", repo_type="dataset")
# open path/room.usd in Isaac Sim 5.1  (or the legacy nycu_light_collider.usd — same content)
```

In Isaac Sim (Python):

```python
import omni.usd
omni.usd.get_context().open_stage(f"{path}/room.usd")
```

### Build your project on top (don't edit the twin)

Reference the foundation onto your own prim and add your layers beside it:

```python
from pxr import Usd, UsdGeom
stage = Usd.Stage.CreateNew("my_project_scene.usd")
UsdGeom.SetStageUpAxis(stage, UsdGeom.Tokens.z)
UsdGeom.SetStageMetersPerUnit(stage, 1.0)
room = UsdGeom.Xform.Define(stage, "/World/Room")
room.GetPrim().GetReferences().AddReference(f"{path}/room.usd")   # foundation, untouched
# ... now add /World/Robot, /World/Furniture, /World/Props as your own prims ...
```

Reference `nycu_lights.usdz` instead if you want the room's **visuals without physics**.

## Physics notes

- Colliders are **static** (no `RigidBodyAPI` on the room) with `physics:approximation = "none"` — the
  exact triangle mesh is used for collision. Correct and cheap for an immovable environment.
- Ground physics material `/Room/PhysicsMaterials/Ground`: `staticFriction 0.9`, `dynamicFriction 0.8`,
  `restitution 0`. Generic and project-neutral — bound at `/Room` (inherits to all room colliders).
- `PhysicsScene` gravity = −Z, 9.81 m/s².

## Notes

- Textures are bundled inside `nycu_lights.usdz` and resolve via relative paths — verified self-contained
  with `UsdUtils.ComputeAllDependencies` (no unresolved dependencies).
- Two references resolve **at runtime** in Isaac Sim / Omniverse and are intentionally not bundled:
  - `OmniGlass.mdl` — Omniverse stock material library.
  - A Cloudy dome-light HDR served from the Omniverse content CDN.
  Materials and dome lighting need an Omniverse asset connection / cache to display fully; geometry, the
  `RectLight`, and all physics load without it.
- Verified to open cleanly in Isaac Sim 5.1 from a fresh download, and to load (443 meshes + colliders)
  when referenced by a downstream scene.

## Citation

If you use this digital twin, please cite it:

```bibtex
@misc{hcislab_ihcll_2026,
  title        = {Intelligent Home Care Living Lab Digital Twin},
  author       = {{Human-centered Intelligent System Lab}},
  year         = {2026},
  howpublished = {Hugging Face dataset},
  url          = {https://huggingface.co/datasets/hcislab/digital-twin},
  note         = {NVIDIA Isaac Sim 5.1 USD digital twin; alias NYCU Room 305}
}
```

A machine-readable `CITATION.cff` is included (Hugging Face renders a "Cite this" entry from it).

## License

**CC BY-NC 4.0** ([Creative Commons Attribution-NonCommercial 4.0](https://creativecommons.org/licenses/by-nc/4.0/)).

- ✅ Share and adapt for **non-commercial** research/education, **with attribution** (cite as above).
- ❌ **No commercial use** without separate permission from the lab. For commercial licensing, contact **hcislab01@gmail.com**.

Note: the referenced `OmniGlass.mdl` and dome-light HDR are NVIDIA Omniverse assets governed by their own licenses; they are not redistributed here.