基于点云配准的果树快速三维重建

    Rapid 3D reconstruction of fruit tree based on point cloud registration

    • 摘要: 旨在为果园生产管理提供果树三维可视化基础数据,该文提出了一种基于点云配准的自然光照环境下的果树三维重构方法。首先,利用RGB-D相机采集不同视角下的果树彩色图像和深度图像,并通过信息融合获取相应视角下果树的三维点云数据;第二,对果树原始点云进行去背景和滤波等预处理,利用归一化对齐径向特征NARF(Normal Aligned Radial Feature)算法计算每片点云中的关键点,并在关键点初运用快速点特征直方图FPFH(Fast Point Feature Histograms)描述子得到关键点的特征向量。通过计算比较两片点云的FPFH特征,寻找两片相邻点云之间的空间映射关系,利用随机抽样一致性RANSAC(RANdomSAmple Consensus)算法提纯映射关系并完成相邻两片点云的初始配准;第三,在初始配准的基础上,利用迭代最近点ICP(Iterative Closest Point)算法完成点云的精确配准;最后,利用上述点云初始配准和精确配准方法对果树多片点云进行全局配准并完整重构果树的三维点云图像。针对配准过程中时间消耗过大的问题,该文提出了基于OpenMP技术对配准进行加速的方法。结果表明,该文所提出的果树三维重构方法具有较高的准确性,配准的平均距离误差为0.0068 m;同时,在不影响配准精度和稳定性的前提下大幅提高了果树三维重建的效率。

       

      Abstract: In order to provide 3D visual image of fruit tree in real-time for guiding orchard production management, a method of 3D reconstruction of fruit tree based on point cloud registration was proposed in this paper.The color images for their corresponding depth of fruit tree were taken by using RGB-D camera from multiple aspect angles.Then 3D point clouds of fruit tree in different perspectives were computed and acquired through fusing the corresponding information of its color image and depth image.And a high-efficiency point cloud registration approach was explored and tested to reconstruct 3D fruit tree’s point cloud model quickly: Firstly, data preprocessing of fruit tree’s each piece of point cloud was carried out for background removing and original point cloud de-noising based on depth distance judgment and spare noise filtering methods respectively, and accordingly each relative accurate data set was obtained as the fruit tree’s point cloud in its each specific perspective.Secondly, the key points of each piece of point cloud were extracted using Normal Aligned Radial Feature (NARF) algorithm based on the depth and boundary information of fruit tree’s point cloud, and their corresponding feature vectors were also calculated using Fast Point Feature Histograms (FPFH) descriptor.Thirdly, the feature vectors were compared between two adjacent pieces of point cloud and then pairs of corresponding key points were estimated and extracted.Then those pairs of corresponding key points were validated and refined using the RANdomSAmple Consensus (RANSAC) algorithm to obtain the correct space mapping relationship between two adjacent pieces of point cloud, and further the transformation parameters from one piece of point cloud to its adjacent one were computed.And then, the initial registration of two adjacent pieces of point cloud was completed by transforming them to the same coordinate system according to their transformation parameters.Fourthly, on the basis of the initial registration, the Iterative Closest Point (ICP) algorithm was implemented to achieve accurate registration for two adjacent pieces of point cloud.Finally, using the initial and precise registration algorithm mentioned above, the remaining pieces of point cloud were globally matched and 3D reconstruction of whole individual fruit tree’s point cloud model was then realized.Moreover, aiming at decreasing the cost of running time of point cloud registration, a program was developed based on the acceleration of OpenMP mechanism, and the efficiency for point cloud registration process was significantly improved with precision and robustness unchanged.The experiment was carried out and the results showed that the proposed approach could be used to match pieces of point cloud at any arbitrary initial positions to reconstruct 3D point cloud for fruit tree rapidly, and its registration distance error was 0.0068 m.

       

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