
基于L1中值骨架提取的植物茎干补全研究
Research on plant stem complement based on L1-medial skeleton extraction
【目的】植物的可视化技术是数字林业研究的重要组成部分。针对植物进行三维点云重建时茎干部分容易缺失的问题,基于拓扑连接的缺失部分位置判断及L1中值骨架提取提出一种茎干补全方法,为实现植物可视化提供技术支撑。【方法】依据概率图模型及最小生成树确定点云簇之间的拓扑连接情况,判断缺失部位所在位置。提出了一种基于搜索的待拟合点点集确定方法,使用基于 L1 中值的局部迭代方法提取茎干点云骨架,并对骨架点集进行排序,确定缺失部分待拟合点。最终使用Bezier曲线拟合缺失部分茎干轴线并使用三维参数圆补全缺失部分点云。【结果】对于叶片与茎干缺失分离的植物点云,茎干补全方法可以真实且有效地对其进行补全,拟合结果整体平滑且具有一定的实际物理意义。【结论】通过三维扫描得到的不完整点云在补全后,能在一定程度上弥补扫描的缺陷,构建出完整且逼真的植物三维点云模型,使其能够更加有效地应用于植物的三维可视化建模。
【Objective】 Plant visualization technology is an important part of digital forestry research. This study used the stem missing points to propose a plant stem complement based on L1-medial skeleton extraction to provide technical support for plant visualization. 【Method】 First, a method to determine the position of the missing part based on topological connection was utilized. Based on the density of the point cloud, the point cloud was classed by using the union-find sets. The weight of the edge of the cluster between nodes was calculated based on the probability graph model, and the minimum spanning tree was used to determine the topological connection between clusters; this enabled the determination of the position of missing parts. Following this, a search-based method was used to determine the set of points to be fitted. The L1-medial local iterative method was used to extract the stem point cloud skeleton. A search algorithm based on nearest neighbor distance was proposed to sort the skeleton point set for the disorder of the point cloud, to determine points to be fitted for missing parts. To address issues with inaccurate skeleton extraction, an iterative optimization method of stem skeleton based on Gauss kernel weight was proposed. This approach used Gauss smoothing stem direction vector, and the Gauss weighted average to calculate stem radius and the updated stem skeleton point set. Finally, a method of point cloud completion of missing parts based on fitting was utilized. The stem radius of missing parts was fitted based on the least squares method, and the stem line of missing parts was fitted based on the Bezier curve. A method based on point cloud density to adjust the generation of the fitting point cloud was proposed to better fit the actual point cloud. 【Result】 The experimental results show that the method proposed in this paper can effectively complete the plant point cloud with leaf and stem missing separation; the fitting result was smooth and has certain practical, physical significance. 【Conclusion】 To some extent, the research results in this paper make up for the defects of scanning, building a complete and realistic three-dimensional point cloud model of plants; this may be more effectively applied to the three-dimensional visual modeling of plants.
三维点云 / 细节补全 / 骨架优化 / 点云排序 / 空间拟合 / 植物可视化技术
3D point cloud / detail completion / skeleton optimization / point cloud sorting / spatial fitting / plant visualization technology
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