> ## Documentation Index
> Fetch the complete documentation index at: https://docs.wuji.tech/llms.txt
> Use this file to discover all available pages before exploring further.

# Model Assets and Loading

This page covers Wuji Hand 2.2 model assets, root links, and loading models in MuJoCo, ROS 2, and Isaac Sim.

* **Root link**: `{l,r}_mount` is the arm flange mount (69 g), shared by the URDF, MJCF, and USD models. The wrist shell is fixed to it through `{l,r}_wrist_fixed`
* **Actuator naming**: `{l,r}_{THJ|FFJ|MFJ|RFJ|LFJ}{0-3}`, with the anatomical naming map in the [Joint Table](https://docs.wuji.tech/docs/en/wuji-hand/latest/control-guide.md#joint-table)

Use the URDF definition as the source of truth for the relationship between the wrist mounting frame and root link. The model formats and available CAD assets ship with the [wuji-description repository](https://github.com/wuji-technology/wuji-description). For the palm mounting interface STEP and A3 dimensioned drawing, see [Mechanical Integration](https://docs.wuji.tech/docs/en/wuji-hand/latest/hardware-integration.md#palm-mounting-interface).

## Model Assets

This page uses the model directories and package names introduced in wuji-description v2026.10.12.

| Category | Contents |
| - | - |
| Model root link | Arm flange mount `{l,r}_mount` |
| Simulation models | Left and right hand URDF (including ROS variants), MJCF, USD, and meshes |
| ROS 2 package | `wuji_hand2_2_description`, rooted at `hand2/hand2_2/body/` |

The models include the arm flange mount and no longer provide a separate `_with_mount` variant.

Models are named `wujihand2_2-{side}`, and the USD entry point is `wujihand2_2.usd`.

## Requirements

| Use | Requirement |
| - | - |
| MuJoCo visualization | Python 3.8+, MuJoCo 2.3+ |
| ROS 2 visualization (RViz) | ROS 2 Lyrical, Ubuntu 26.04 |
| Isaac Sim USD | Isaac Sim 2024.x+ |
| STEP / CAD | Any CAD tool that reads STEP, such as FreeCAD or SolidWorks |

## Get and Load

```bash theme={null}
git clone https://github.com/wuji-technology/wuji-description.git
cd wuji-description
```

MuJoCo:

```bash theme={null}
# Right hand
python -m mujoco.viewer --mjcf=hand2/hand2_2/body/mjcf/right.xml

# Left hand
python -m mujoco.viewer --mjcf=hand2/hand2_2/body/mjcf/left.xml

```

MJCF collision geometry is the convex hull of each link mesh. The 27 links with meshes participate in collision, with 15 body pairs excluded by the model configuration, so inter-finger and fingertip-to-palm contacts stay live. Display layers are group 1 visual, group 2 collision, and group 3 fingertip sites.

For dependencies, description packages, and launch commands, see [ROS 2 Integration](https://docs.wuji.tech/docs/en/wuji-hand/latest/ros2-integration.md).

Isaac Sim USD:

| Variant | Path |
| - | - |
| Left hand | `hand2/hand2_2/body/usd/left/wujihand2_2.usd` |
| Right hand | `hand2/hand2_2/body/usd/right/wujihand2_2.usd` |

The USD is a layered asset with base, physics, robot, and sensor sublayers plus the logo texture. Keep the complete contents of each `usd/{left,right}/` directory. The root prim is `wujihand2_2_{side}`. Drive gains hold the current pose when you select **Play**.

URDF preview requires Rust/Cargo. See the [urdf-viz installation guide](https://github.com/openrr/urdf-viz#install).

URDF preview:

```bash theme={null}
cargo install urdf-viz
urdf-viz hand2/hand2_2/body/urdf/right.urdf
```

## Verify

1. Confirm MuJoCo or the URDF viewer opens with no missing meshes
2. Confirm the model shows 20 revolute joints
3. Confirm the directory and ROS 2 package name match 2.2

Loading the model confirms that the assets, paths, and visualization pipeline work. Firmware, networking, sensors, and real device control need a connected device to verify.


This documentation is built and hosted on [Mintlify](https://mintlify.com), a developer documentation platform.