VRoot is an immersive extended reality reconstruction tool for root system architectures from 3D volumetric scans of soil columns. We have conducted a laboratory user study to assess the performance of new users with our software in comparison to established software. We utilize a plant model to derive a synthetic root architecture, providing a baseline for reconstruction. This demo showcases the processes and techniques contributing to exact and efficient manual root architecture reconstruction in Virtual Reality. The extraction task typically is the sparse graph-structure extraction from a 3D magnetic-resonance imaging (MRI) data set. We visualize the RSA directly within the MRI and offer selection-set-based methods of adapting and augmenting the root architecture. This application is in productive use at our partner institute, where it is used to analyze complex root images.

Tracking the temporal evolution of features in time-varying data is a key method in visualization. For typical feature definitions, such as vortices, objects are sparsely distributed over the data domain. In this paper, we present a novel approach for tracking both sparse and space-filling features. While the former comprise only a small fraction of the domain, the latter form a set of objects whose union covers the domain entirely while the individual objects are mutually disjunct. Our approach determines the assignment of features between two successive time-steps by solving two graph optimization problems. It first resolves one-to-one assignments of features by computing a maximum-weight, maximum-cardinality matching on a weighted bi-partite graph. Second, our algorithm detects events by creating a graph of potentially conflicting event explanations and finding a weighted, independent set in it. We demonstrate our method's effectiveness on synthetic and simulation data sets, the former of which enables quantitative evaluation because of the availability of ground-truth information. Here, our method performs on par or better than a well-established reference algorithm. In addition, manual visual inspection by our collaborators confirm the results' plausibility for simulation data.