高天寒,杨子艺(东北大学软件学院, 沈阳 110000;东北大学软件学院交互式媒体与计算技术研究所, 沈阳 110000)
目的 传统增量式运动结构恢复算法中，初始图像对选择鲁棒性差，增量求解过程效率较低，捆绑调整策略存在计算冗余，模型修正后仍存在较大误差。为解决上述问题，以基于图像序列的3维重建为基础，提出一种新的增量式运动结构恢复算法（SFM-Y）。方法 首先，采用改进的自适应异常值过滤方法增强初始图像对选择的鲁棒性，得到用于初始重建的初始图像对；其次，通过增量迭代重建丰富点云模型，采用改进的EPNP（efficient perspective-n-point）解算方法提高增量添加过程的计算效率和精确度；最后，采用优化的捆绑调整策略进行模型修正，解决模型漂移问题，修正重投影误差。结果 实验选取不同数据规模的数据集，在本文方法及传统方法间进行测试对比，以便更加全面地分析算法性能。实验结果表明，SFM-Y算法相比传统的增量式运动结构恢复算法，在计算效率和结果质量方面均有所提高，根据性能分析对比的结果所示，本文方法较传统方法在计算效率和重建精度上约有10%的提升。结论 提出的增量式运动结构恢复算法能够高效准确地实现基于图像序列的3维重建优于传统方法，计算效率较高，初始重建鲁棒性强，生成模型质量较好。
Revised image-sequence-based incremental structure from motion algorithm
Gao Tianhan,Yang Ziyi(Software College, Northeastern University, Shenyang 110000, China;Interactive Media and Computing Technology Institute, Software College, Northeastern University, Shenyang 110000, China)
Objective With the fast development of virtual reality technology, determining how to establish virtual scenes rapidly and realistically becomes a bottleneck that restricts the popularization and promotion of virtual reality technology. As an important technical means to solve this problem, 3D reconstruction technology has been applied in many fields, such as ancient building protection and restoration, medical treatment, and tourism. Such technology has been developing continuously in recent years, and its application scenarios have been extended greatly. The scale of data to be processed has also increased substantially, and the accuracy requirements for reconstruction results have continuously increased. In these cases, many problems existing in the traditional methods are exposed. For instance, problems such as poor robustness of initial image pair selection process, inefficient incremental solving process, redundant calculation of bundle adjustment, and errors that remain after model correction are found in the traditional incremental structure from motion algorithm. Accordingly, this study proposes a new incremental structure from motion algorithm (named SFM-Y) based on the foundation called image sequence-based 3D reconstruction. Method First, an improved adaptive outlier-filtering method is proposed to enhance the robustness of the initial image selection in this study. Next, an adaptive threshold estimation model is introduced into our algorithm, and constraints and filter conditions are added to improve the robustness of initial image selection and initial reconstruction to resolve the robustness problem caused by the threshold, which is set manually, used in the RANSAC (random sample consensus) filter process. The constraints include four-point method inspection, wide baseline constraint, and revised five-point outlier culling method. In this way, the initial image pair that is used to perform initial reconstruction is selected with strong robustness. Second, the proposed method processes incremental iterative reconstruction to enrich the point cloud model. In this process, the improved efficient perspective-n-point solution method is proposed to improve the computational efficiency and accuracy of the incremental addition process. The solution method combines the idea of weighted refinement and the method of how to reduce a linear system’s algebraic error. We try to give this method a rigorous derivation process to prove that it is an efficient solution to the question of how to accelerate the incremental solution process of the incremental structure from motion algorithm. Finally, an optimized bundling adjustment strategy is used to modify the model, solve the model drift, and revise the re-projection error. In this stage, the integration of graphics is checked by introducing a minimum triangulation angle and performing re-triangulation on the tracks among different projection points. Then, once or twice iterative optimization (including global bundle adjustment, filtering, and re-triangulation process) is executed to ameliorate the result of our algorithm. All the methods mentioned above that we performed or revised work together to complete a common goal, reducing solution time and improving reconstruction quality. Result Among all the experiments mentioned in this paper, we select data sets in different data scales first. A comparison and test are then performed among the methods involved in this study to comprehensively and objectively analyze the algorithm performance and acquire a convincing result. Experimental results show that the SFM-Y algorithm improves the computational efficiency and quality of results compared with the traditional incremental motion structure recovery algorithm. The performance analysis and comparison results indicate that the proposed method is more efficient than the traditional method. The reconstruction accuracy yields 10% improvement compared with that of the traditional algorithm referred to in this study. Conclusion After a series of analyses, arguments, and experiments, the following conclusions are drawn. Experiments in many databases show that the new incremental motion structure restoration algorithm (SFM-Y) proposed in this study can efficiently and accurately achieve the goal of 3D reconstruction based on image sequences. This algorithm provides a new way of thinking in the field of incremental structure from motion algorithm, which certainly has a positive promoting effect on the development of 3D reconstruction research and has great meaning for the following research and exploration. The proposed algorithm is better than traditional methods and has the advantages of high computational efficiency, strong initial reconstruction robustness, and high quality of the generated model.