Update README.md

README.md

@@ -1,3 +1,19 @@
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-license: apache-2.0
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+---
+license: apache-2.0
+---
+
+## FlowOcc3D (flow dataset)
+
+Download [FlowOcc3D](https://drive.google.com/file/d/1Xo2A40bUYA1wwXxqi_y6sQqu5mRRkc-s/view?usp=sharing). Unzip it in `./data/nuscenes`.
+
+Here we briefly introduce what the downloaded file looks like. We store the flow and index of the foreground voxels in the `.bin` file and the `_idx.bin` file.
+```python
+W, H, Z = 200, 200, 16
+sample_idx = results['sample_idx'] # nuScenes sample token
+data_path = os.path.join('./data/nuscenes', 'occ_flow_sparse_ext', sample_idx)
+
+occ_flow = np.ones((W*H*Z, 2)) * pad_value # pad_value could be zero
+sparse_flow = np.fromfile(data_path + '.bin', dtype=np.float16).reshape(-1, 3)[:, :2]
+sparse_idx = np.fromfile(data_path + '_idx.bin', dtype=np.int32).reshape(-1)
+occ_flow[sparse_idx] = sparse_flow
+occ_flow = occ_flow.reshape(W, H, Z, 2)