docs: add Pose convention section (zrdt-270 Option B) (#2)

- docs: add Pose convention section (zrdt-270 Option B) (32815dd009f59738baa20663064362d24b740095)


Co-authored-by: Umit Kavala <ukavala@users.noreply.huggingface.co>

README.md

@@ -152,9 +152,21 @@ _A `datasets.load_dataset()` loader is planned for v1.1._
 
 Training 6D pose estimation models, bin-picking grasp models, and warehouse robotics perception systems. Synthetic data for sim-to-real transfer research.
 
+## Pose convention
+
+This release (v1.0 and v1.1) ships 6D poses in **OpenGL/Blender camera convention** (camera looks down `-Z`, in-front objects have `cam_t_m2c.z < 0`) rather than the BOP-standard **OpenCV convention** (camera looks down `+Z`, in-front objects have `cam_t_m2c.z > 0`). The two differ by the basis change `diag(1, -1, -1)` applied to the camera frame.
+
+**Anyone scoring against bop_toolkit_lib, MegaPose, FoundationPose, CosyPose, or any OpenCV-convention model must apply `diag(1, -1, -1)` to the GT `cam_R_m2c` and `cam_t_m2c` from `scene_gt.json` before evaluation**, otherwise pose errors blow up to the order of the object diameter (~150 mm) and any AR comparison is meaningless.
+
+ZereData's evaluation harness exposes this via the `--legacy-gl-convention` flag on `eval.scorer.BopScorer`, `eval.adapter.gt_as_predictions`, and the eval CLIs (`gt_sanity`, `run_megapose_eval`, `rescore`, `_perturb_probe`, `rescore_h1`). Pass it when scoring v1.0 or v1.1; omit it for v1.2 onward, which ships in OpenCV convention at the producer (see [zrdt-269](https://github.com/umitkavala/zere-synth/commit/018b959) for the producer-side fix).
+
+This deviation was identified post-publication. v1.0 and v1.1 remain available unchanged on HuggingFace for reproducibility; **v1.2 supersedes them for new integrations** and ships BOP-spec compliant out of the box. The legacy flag is supported indefinitely so downstream code that already ingests v1.0/v1.1 keeps working.
+
+RGB, depth, masks, COCO 2D boxes, and YOLO labels are **unaffected** — only the 6D pose serialisation deviates from the BOP spec.
+
 ## Limitations and Known Issues
 
-- **BOP coordinate convention.** Object pose extrinsics in `scene_gt.json` are exported in OpenGL convention (negative-Z forward) rather than the BOP-standard OpenCV convention (positive-Z forward). Downstream consumers should apply a `diag(1, -1, -1)` transform when scoring against BOP toolkit baselines. A v1.x patch release with the producer-side fix is in progress.
+- **BOP pose convention deviation.** Object pose extrinsics in `scene_gt.json` ship in OpenGL convention, not BOP-spec OpenCV. See the **Pose convention** section above for the basis change and the `--legacy-gl-convention` flag. v1.2 supersedes this with a producer-side fix.
 - **Warehouse-specific lighting.** The three lighting profiles model warehouse conditions and may not transfer directly to outdoor, medical, or agricultural domains:
     - `bin_picking_overhead` — bright fluorescent overhead panels, typical of distribution-center shelving aisles.
     - `bin_picking_mixed` — mixed overhead + rim lighting with warmer colour temperature, mimicking older facilities with partial skylights.