Visual Analysis of Dimensionality Reduction in an Interactive Virtual Environment for Exploring Bat Flight Kinematics

We present an experiment to study two approaches for modeling complex skeletal motion of a bat in flight. Both the domain-enhancement approach and the data-fidelity approach use proper orthogonal decomposition (POD) to study animal locomotion. The motion was displayed in a fishtank virtual environment (VE) with a threedimensional user interface (3D UI) that supports flight comparison. The UI design was evaluated by biologists and engineering scientists, who explored the linear combinations of individual components described by POD and subsequently uncovered and verified patterns in animal locomotion using the two approaches. Our experimental results suggest that displaying experimental kinematics data in an interactive 3D visualization system gave the scientists an intuitive biological interpretation of biomechanical patterns of animal flight. In particular, feedback from experts who compared this environment with traditional two-dimensional (2D) graphs stressed the advantage of seeing inherently 3D data in a VE, letting them concentrate more readily on particular aspects of data analyses. Subsequently, they were able to notice new motion patterns as well as differences and similarities in flight behaviors. Comparison of the two modeling methods shows similarities in the types of motions presented.