---
pretty_name: AFUN
license: cc-by-nc-sa-4.0
language:
- en
size_categories:
- 10K<n<100K
tags:
- robotics
- affordance
- manipulation
- 3d-motion
- segmentation
---

# AFUN

Training data of **AFUN** ([arXiv:2606.02551](https://arxiv.org/abs/2606.02551)):
**44,749 data points** for affordance segmentation and 3D interaction-motion prediction.
Each data point is one folder: an RGB frame, its depth map, the ground-truth affordance
mask, the ground-truth 3D motion, and a language instruction.

## Download & extract

```bash
pip install -U huggingface_hub
hf download AFUN-dataset/AFUN --repo-type dataset --local-dir afun_train
cd afun_train
for f in data/*.tar.zst; do tar --zstd -xf "$f"; done
```

Download ≈ 231 GiB, extracted ≈ 522 GiB. After extraction:

```
afun_train/
├── manifest.json                        # index — one entry per data point
└── <source>/<episode>/<interval>/<cam>/ # 44,749 folders
    ├── obs_frame.png                    # RGB frame
    ├── obs_frame_depth.npy              # float32 H×W depth, millimeters
    ├── sam_mask.png                     # affordance mask (non-zero = actionable region)
    └── trajectory.json                  # 3D motion + camera intrinsics
```

## Load a data point

```python
import json, numpy as np
from PIL import Image

m = json.load(open("manifest.json"))
s = m["samples"][0]
rgb   = np.array(Image.open(f"{s['path']}/obs_frame.png"))
depth = np.load(f"{s['path']}/obs_frame_depth.npy")          # millimeters
mask  = np.array(Image.open(f"{s['path']}/sam_mask.png")) > 0
traj  = json.load(open(f"{s['path']}/trajectory.json"))
print(s["language"], traj["camera_info"]["intrinsics"])
```

Each manifest entry has `path` (the folder), `dataset` / `episode_id` / `interval` / `cam`,
the instruction (`language`, with variants in `queries`), and `shard` (which archive
contains it).

## trajectory.json

3D positions are in the **camera frame, in meters**. `camera_info` holds the intrinsics
(`fx, fy, cx, cy`), the distortion model, and `T_base_to_cam`.

There are **two schemas**, because SceneFun3D scenes are annotated differently from robot
and human videos:

**A. Robot / human sources** (`droid`, `robomind`, `agibot`, `rh20t`, `rh20t_human`,
`calvin`, `rlbench`, `vitra`) — one interaction per file, fields at the top level:

| field | meaning |
|---|---|
| `trajectory_3d` | GT motion of the interaction point, `[{frame_idx, position_3d}, ...]` — the curve-fitted (denoised) track |
| `motion_2d` | start / end pixel of the motion |
| `spline_params.ctrl` | control points of the fitted 3D curve (the training target is sampled from this curve) |

**B. `scenefun3d`** — SceneFun3D is a set of annotated 3D scans, not videos. A scene can
have several annotated functional parts (a drawer, a window, a tap), so the motions live in
a **list** called `trajectories`, one entry per annotation. Each entry has the same fields
as schema A (`trajectory_3d`, `motion_2d`, `spline_params`) plus:

| field | meaning |
|---|---|
| `annot_id` | the original SceneFun3D annotation id |
| `interval_language` | the instruction for *this* annotation |
| `motion_type` | `rot` (hinged: door, window) or `trans` (sliding: drawer) |
| `scenefun3d_motion_params` | the analytic motion (see below) |

`scenefun3d_motion_params` is what makes this source distinctive — the motion is given in
closed form, not just as samples:

- `motion_type: "rot"` → `motion_dir_cam` (rotation axis), `origin_cam` (a point on the
  axis, i.e. the hinge), `ref_cam` (reference point), `angle_rad` (e.g. `1.5708` = 90°)
- `motion_type: "trans"` → `motion_dir_cam` (slide direction), `origin_cam` (start point),
  `distance_m` (e.g. `0.3`), `orient` (`inwards` / `outwards`)

`trajectory_3d` is 15 points sampled from those parameters.
**In practice `trajectories` has length 1** (~95% of files; the rest have 2).

Reading either schema:

```python
traj = json.load(open(f"{s['path']}/trajectory.json"))
if "trajectories" in traj:          # scenefun3d
    motion = traj["trajectories"][0]     # [0] is enough for almost every file
else:                               # robot / human sources
    motion = traj
points = [p["position_3d"] for p in motion["trajectory_3d"]]   # camera frame, meters
```

## Sources

| key | dataset | data points |
|---|---|---:|
| scenefun3d | SceneFun3D | 39,772 |
| robomind | RoboMIND | 2,197 |
| vitra | VITRA (human videos) | 1,205 |
| droid | DROID | 816 |
| rh20t_human | RH20T human demos | 315 |
| agibot | AgiBot World | 299 |
| rh20t | RH20T | 93 |
| calvin | CALVIN | 46 |
| rlbench | RLBench | 6 |

The evaluation sets are released separately as [**AFUN_eval**](https://huggingface.co/datasets/AFUN-dataset/AFUN_eval) and are disjoint from this
set at the sample level.

## Citation

```bibtex
@article{wang2026afun,
  title   = {AFUN: Towards an Affordance Foundation Model for Functionality Understanding},
  author  = {Wang, Zhaoning and Zhong, Yi and Fu, Jiawei and Christensen, Henrik I. and Gao, Jun},
  journal = {arXiv preprint arXiv:2606.02551},
  year    = {2026}
}
```