News

• [2023/08]: The CTF-Occ and several baseline models have been released for both Nuscene and Waymo dataset by Yucheng Mao.
• [2023/06]: The preprint version is available on arXiv.

Table of Contents

• Introduction
• Data
  • Basic Information
  • Occ3D-Waymo
  • Occ3D-nuScenes
• Getting Started
• License

Introduction

This paper propose 3D Occupancy Prediction, a general and comprehensive 3D perception task for vision-based robotic applications. Occupancy prediction can represent both the semantics and geometry of any scene effectively. We develop a rigorous label generation pipeline for occupancy prediction, construct two challenging datasets (Occ3D-Waymo and Occ3d-nuScenes) and establish a benchmark together with evaluation metrics to facilitate future research. In addition, we propose a novel CTF-Occ network that achieves outstanding occupancy prediction performance. For more information, please refer to the Paper.

Data

Basic Information

• How are the labels annotated? The ground truth labels of occupancy derive from accumulative LiDAR scans with human annotations.

  • If a voxel reflects a LiDAR point, then it is assigned as the same semantic label as the LiDAR point;
  • If a LiDAR beam passes through a voxel in the air, the voxel is set to be free;
  • Otherwise, we set the voxel to be unknown, or unobserved. This happens due to the sparsity of the LiDAR or the voxel is occluded, e.g. by a wall. In the dataset, [mask_lidar] is a 0-1 binary mask, where 0 represent unobserved voxels. As shown in Fig.1(b), grey voxels are unobserved. Due to the limitation of the visualization tool, we only show unobserved voxels at the same height as the ground.

• Camera visibility. Note that the installation positions of LiDAR and cameras are different, therefore, some observed voxels in the LiDAR view are not seen by the cameras. Since we focus on a vision-centric task, we provide a binary voxel mask [mask_camera], indicating whether the voxels are observed or not in the current camera view. As shown in Fig.1(c), white voxels are observed in the accumulative LiDAR view but unobserved in the current camera view.

• Both [mask_lidar] and [mask_camera] masks are optional for training. Only [mask_camera] is used for evaluation; the unobserved voxels are not involved during calculating the mIoU. Since Waymo only has 5 cameras and does not provide a 360-degree surround view, we additionally provide [mask_fov].

• We generate two 3D occupancy prediction datasets, Occ3D-Waymo and Occ3D-nuScenes. The detailed descriptions of each dataset are as follows.

Occ3D-Waymo

• The dataset contains 15 classes. The definition of classes from 0 to 14 is TYPE_GENERALOBJECT, TYPE_VEHICLE, TYPE_PEDESTRIAN, TYPE_SIGN, TYPE_CYCLIST, TYPE_TRAFFIC_LIGHT, TYPE_POLE, TYPE_CONSTRUCTION_CONE, TYPE_BICYCLE, TYPE_MOTORCYCLE, TYPE_BUILDING, TYPE_VEGETATION, TYPE_TREE_TRUNK, TYPE_ROAD, TYPE_WALKABLE.The label 15 category represents voxels that are not occupied by anything, which is named as free. Voxel semantics for each sample frame is given as [semantics] in the labels.npz. Please note that there is a slight difference between the Occ classes and the classes used in the Waymo LiDAR segmentation.

• After download and unzip files, the hierarchy of folder Occ3D-Waymo/ is described below:

  └── Occpancy3D-Waymo
      |
      ├── training
      |   ├── 000
      |   |   ├── 000.npz
      |   |   ├── 000_04.npz
      |   |   ├── 001.npz
      |   |   ├── 001_04.npz
      |   |   ├── 002.npz
      |   |   ├── 002_04.npz
      |   |   └── ...
      |   |     
      |   ├── 001
      |   |   ├── 000.npz
      |   |   ├── 000_04.npz
      |   |   └── ...
      |   ├── ...
      |   |
      |   └── 797
      |       ├── 000.npz
      |       ├── 000_04.npz
      |       └── ...
      |
      ├── validation
      |   ├── 000
      |   |   └── ...
      |   ├── ...
      |   |
      |   └── 201
      |       ├── 000.npz
      |       ├── 000_04.npz
      |       └── ...
      |
      └── test
          └── ...
  
  

  • training/validation/test contains data for each scene, each scene includes corresponding ground truth of each frame.
  • *.npz contains [voxel_label], [origin_voxel_state], [final_voxel_state] , and [infov] for each frame. We provide two types of voxel size data, with voxel size of 0.1m and 0.4m, respectively. *_04.npz represents the data with a voxel size of 0.4m.

    import numpy as np
    data = np.load("010/105.npz")
    semantics, mask_lidar, mask_camera, mask_fov = data['voxel_label'], data['origin_voxel_state'], data['final_voxel_state'], data['infov']
    print(semantics.shape)
    print(np.unique(semantics))
    

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Occ3D-nuScenes

• The dataset contains 18 classes. The definition of classes from 0 to 16 is the same as the nuScenes-lidarseg dataset. The label 17 category represents free. Voxel semantics for each sample frame is given as [semantics] in the labels.npz.

• The hierarchy of folder Occpancy3D-nuScenes-V1.0/ is described below:

  └── Occpancy3D-nuScenes-V1.0
      |
      ├── mini
      |
      ├── trainval
      |   ├── imgs
      |   |   ├── CAM_BACK
      |   |   |   ├── n015-2018-07-18-11-07-57+0800__CAM_BACK__1531883530437525.jpg
      |   |   |   └── ...
      |   |   ├── CAM_BACK_LEFT
      |   |   |   ├── n015-2018-07-18-11-07-57+0800__CAM_BACK_LEFT__1531883530447423.jpg
      |   |   |   └── ...
      |   |   └── ...
      |   |     
      |   ├── gts  
      |   |   ├── [scene_name]
      |   |   |   ├── [frame_token]
      |   |   |   |   └── labels.npz
      |   |   |   └── ...
      |   |   └── ...
      |   |
      |   └── annotations.json
      |
      └── test
          ├── imgs
          └── annotations.json
  
  

  • imgs/ contains images captured by various cameras.
  • gts/ contains the ground truth of each sample. [scene_name] specifies a sequence of frames, and [frame_token] specifies a single frame in a sequence.
  • annotations.json contains meta infos of the dataset.
  • labels.npz contains [semantics], [mask_lidar], and [mask_camera] for each frame.

  annotations {
      "train_split": ["scene-0001", ...],                         <list> -- training dataset split by scene_name
      "val_split": list ["scene-0003", ...],                      <list> -- validation dataset split by scene_name
      "scene_infos" {                                             <dict> -- meta infos of the scenes    
          [scene_name]: {                                         <str> -- name of the scene.  
              [frame_token]: {                                    <str> -- samples in a scene, ordered by time
                      "timestamp":                                <str> -- timestamp (or token), unique by sample
                      "camera_sensor": {                          <dict> -- meta infos of the camera sensor
                          [cam_token]: {                          <str> -- token of the camera
                              "img_path":                         <str> -- corresponding image file path, *.jpg
                              "intrinsic":                        <float> [3, 3] -- intrinsic camera calibration
                              "extrinsic":{                       <dict> -- extrinsic parameters of the camera
                                  "translation":                  <float> [3] -- coordinate system origin in meters
                                  "rotation":                     <float> [4] -- coordinate system orientation as quaternion
                              }   
                              "ego_pose": {                       <dict> -- vehicle pose of the camera
                                  "translation":                  <float> [3] -- coordinate system origin in meters
                                  "rotation":                     <float> [4] -- coordinate system orientation as quaternion
                              }                
                          },
                          ...
                      },
                      "ego_pose": {                               <dict> -- vehicle pose
                          "translation":                          <float> [3] -- coordinate system origin in meters
                          "rotation":                             <float> [4] -- coordinate system orientation as quaternion
                      },
                      "gt_path":                                  <str> -- corresponding 3D voxel gt path, *.npz
                      "next":                                     <str> -- frame_token of the previous keyframe in the scene 
                      "prev":                                     <str> -- frame_token of the next keyframe in the scene
                  }
              ]             
          }
      }
  }
  

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Getting Started

We will release the code soon.

Citation

If you find our work useful for your research, please consider citing the paper:

@article{tian2023occ3d,
  title={Occ3D: A Large-Scale 3D Occupancy Prediction Benchmark for Autonomous Driving},
  author={Tian, Xiaoyu and Jiang, Tao and Yun, Longfei and Wang, Yue and Wang, Yilun and Zhao, Hang},
  journal={arXiv preprint arXiv:2304.14365},
  year={2023}
}

License

Before using the dataset, you should register on the website and agree to the terms of use of the nuScenes and Waymo. The code used to generate the data and the generated data are both subject to the MIT License.

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