PVI-DSO: Leveraging Planar Regularities for Direct Sparse Visual-Inertial Odometry

The monocular Visual-Inertial Odometry (VIO) based on the direct method can leverage all the available pixels in the image to estimate the camera motion and reconstruct the environment. The denser map reconstruction provides more information about the environment, making it easier to extract structure and planar regularities. In this paper, we propose a monocular direct sparse visual-inertial odometry, which exploits the plane regularities (PVI-DSO). Our system detects coplanar information from 3D meshes generated from 3D point clouds and uses coplanar parameters to introduce coplanar constraints. In order to reduce computation and improve compactness, the plane-distance cost is directly used as the prior information of plane parameters. We conduct ablation experiments on public datasets and compare our system with other state-of-the-art algorithms. The experimental results verified leveraging the plane information can improve the accuracy of the VIO system based on the direct method

Visual Odometry Using Line Features and Machine Learning Enhanced Line Description

The research on 2D lines in images has increased strongly in the last decade; on the one hand, due to more computing power available, on the other hand, due to an increased interest in odometry methods and autonomous systems. Line features have some advantages over the more thoroughly researched point features. Lines are detected on gradients, they do not need texture to be found. Thus, as long as there are gradients between homogeneous regions, they can cope with difficult situations in which mostly homogeneous areas are present. By being detected on gradients, they are also well suited to represent structure. Furthermore, lines have a very high accuracy orthogonal to their direction, as they consist of numerous points which all lie on the gradient contributing to this locational accuracy. First, we introduce a visual odometry approach which achieves real-time performance and runs solely using lines features, it does not require point features. We developed a heuristic filter algorithm which takes neighbouring line features into account and thereby improves tracking of lines and matching of lines in images taken from arbitrary camera locations. This increases the number of tracked lines and is especially beneficial in difficult scenes where it is hard to match lines by tracking them. Additionally, we employed the Cayley representation for 3D lines to avoid overparameterization in the optimization. To show the advancement of the method, it is benchmarked on commonly used datasets and compared to other state of the art approaches. Second, we developed a machine learning based line feature descriptor for line matching. This descriptor can be used to match lines from arbitrary camera locations. The training data was created synthetically using the Unreal Engine 4. We trained a model based on the ResNet architecture using a triplet loss. We evaluated the descriptor on real world scenes and show its improvement over the famous Line Band Descriptor. Third, we build upon our previous descriptor to create an improved version. Therefor, we added an image pyramid, gabor wavelets and increased the descriptor size. The evaluation of the new descriptor additionally contains competing new approaches which are also machine learning based. It shows that our improved approach outperforms them. Finally, we provide an extended evaluation of our descriptor which shows the influences of different settings and processing steps. And we present an analysis of settings for practical usage scenarios. The influence of a maximum descriptor distance threshold, of a Left-Right consistency check and of a descriptor distance ratio threshold between the first and second best match were investigated. It turns out that, for the ratio of true to false matches, it is almost always better to use a descriptor distance ratio threshold than a maximum descriptor distance threshold

Direct line guidance odometry

Modern visual odometry algorithms utilize sparse point-based features for tracking due to their low computational cost. Current state-of-the-art methods are split between indirect methods that process features extracted from the image, and indirect methods that deal directly on pixel intensities. In recent years, line-based features have been used in SLAM and have shown an increase in performance albeit with an increase in computational cost. In this paper, we propose an extension to a point-based direct monocular visual odometry method. Here we that uses lines to guide keypoint selection rather than acting as features. Points on a line are treated as stronger keypoints than those in other parts of the image, steering point-selection away from less distinctive points and thereby increasing efficiency. By combining intensity and geometry information from a set of points on a line, accuracy may also be increased