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data_demo/README.md

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+# Demo data layout (`data_demo/`)
+
+All demo cases read from this folder. Download from
+[Hugging Face — PiLoT-data](https://huggingface.co/datasets/choyaa/PiLoT-data):
+
+```bash
+# from PiLoT repo root
+./scripts/download_data_demo.sh
+```
+
+Partial downloads: `./scripts/download_data_demo.sh feicuiwan` or `smbu`.
+
+```
+data_demo/
+├── 3dgs_model/                 # Feicuiwan / Jadebay PLY
+│   └── point_cloud.ply
+├── smbu_model/                 # SMBU CityGaussian checkpoint + COLMAP sparse
+│   ├── checkpoints/
+│   │   └── epoch=60-step=30000.ckpt
+│   └── sparse/sparse/0/
+├── pretrained_model/           # PiLoT refiner weights (shared by all cases)
+│   └── model@mapscape@512@Fourier.ckpt
+└── query/
+    ├── images/
+    │   ├── 3dgs_test/        # Feicuiwan query frames
+    │   └── smbu_seq2/        # SMBU query frames
+    └── poses/
+        ├── 3dgs_test.txt       # lon lat alt roll pitch yaw
+        └── smbu_seq2.txt       # x y z pitch roll yaw (normalized)
+```
+
+## Pose formats
+
+| File | Columns |
+|------|---------|
+| `3dgs_test.txt` | `name lon lat alt roll pitch yaw` |
+| `smbu_seq2.txt` | `name x y z pitch roll yaw` |
+
+## Local development note
+
+If disk space is tight, `smbu_model/` may be a symlink to your CityGaussian
+training output. The Hugging Face release ships real checkpoint files under
+`data_demo/smbu_model/`.
+
+| Variable | Default |
+|----------|---------|
+| `SMBU_MODEL_DIR` | `data_demo/smbu_model` |
+| `CITYGAUSSIAN_ROOT` | `third_party/CityGaussian` |