adapters/ob3d/reencoding_script.md

OB3D Re-encoding — exact procedure

Upstream layout (input)

OB3D ships dense cubemap RGB-D-pose trajectories. Place the upstream data under data/ob3d/ matching this layout:

data/ob3d/
├── <scene_name>-Egocentric/
│   ├── cubemap/
│   │   ├── px/{frame_NNNN.png, frame_NNNN_depth.npy}      # +X face
│   │   ├── nx/                                            # -X face
│   │   ├── py/, ny/, pz/, nz/                             # remaining faces
│   ├── pose/
│   │   └── pose_NNNN.json                                  # source pose convention
│   └── …
└── <scene_name>-Non-Egocentric/
    └── (same structure)

The exact upstream filenames depend on which OB3D distribution you use; the pipeline.py reads the layout from config.yaml so adjust input_layout there if needed.

Output schema (CM-EVS unified)

outputs/ob3d/<scene_name>-<viewpoint>/
├── meta.json                                    # coordinate convention, first-frame center
├── panorama_0000.png                            # ERP RGB, 1600×800
├── panorama_0000_depth.npy                      # ERP range depth (m), float32
├── pose_0000.json                               # { qwc: [w,x,y,z], position: [x,y,z], camera_type: "cubemap_reencoded" }
├── panorama_0001.png
├── panorama_0001_depth.npy
├── pose_0001.json
└── …

Run

cd ../../code
python scripts/reencode_outdoor.py \
    --source ob3d \
    --config ../adapters/ob3d/config.yaml

The script:

1. Loads config.yaml → resolves cubemap face size, axis conversion, ERP target resolution.
2. For each scene/viewpoint listed in metadata/source_manifest.json:
   • Reads the 6 cubemap faces per frame, concatenates into ERP via standard cubemap → equirectangular projection.
   • Re-projects depth: cubemap perspective z → ERP range depth (radial).
   • Reads source pose, converts axis convention to CM-EVS world frame, expresses as q_wc + position.
   • Writes the triple panorama_NNNN.{png, _depth.npy} and pose_NNNN.json.
3. Emits per-scene meta.json re-stating the coordinate convention.

Verifying against paper

After running, compare with paper §4.3 Table 4:

• 12 scenes × 2 viewpoints = 24 instances ✓
• 200 frames each = 2,400 frames ✓
• Resolution 1600×800 ✓
• Median depth 3.88 m ✓ (sanity-check via your favorite stats script)

Caveats

• No curator selection. Paper §4.2 Table 3 row "Outdoor / OB3D" notes that all v1.0 outdoor frames are full re-encoded source trajectories, not curator-selected subsets. Therefore no metadata/per_step_log.jsonl is emitted.
• License: frames produced by this adapter remain under upstream OB3D license. Do not redistribute without checking upstream terms.