  Analyzing complex and large data as generated in non-destructive testing
(NDT) is a time-consuming and mentally demanding challenge. Such data is
heterogeneous and integrates primary and secondary derived data from materials
or material systems for spatial, spatio-temporal as well as high-dimensional
data analysis. Currently, materials experts mainly rely on conventional desktop
systems using standard 2D visualization techniques for this purpose. Our
framework is a novel immersive visual analytics system, which supports the
exploration of complex spatial structures and derived multidimensional abstract
data in an augmented reality setting. It includes three novel visualization
techniques: MDD-Glyphs, TimeScatter, and ChronoBins, each facilitating the
interactive exploration and comparison of multidimensional distributions from
multiple datasets and time steps. A qualitative evaluation conducted with
materials experts and novices in a real-world case study demonstrated the
benefits of the proposed visualization techniques. This evaluation also
revealed that combining spatial and abstract data in an immersive environment
improved their analytical capabilities and facilitated to better and faster
identify patterns, anomalies, as well as changes over time.
