  We present the 3D Trajectory-based Stress Visualizer (3D-TSV), a visual
analysis tool for the exploration of the principal stress directions in 3D
solids under load. 3D-TSV provides a modular and generic implementation of key
algorithms required for a trajectory-based visual analysis of principal stress
directions, including the automatic seeding of space-filling stress lines,
their extraction using numerical schemes, their mapping to an effective
renderable representation, and rendering options to convey structures with
special mechanical properties. In the design of 3D-TSV, several perceptual
challenges have been addressed when simultaneously visualizing three mutually
orthogonal stress directions via lines. We present a novel algorithm for
generating a space-filling and evenly spaced set of mutually orthogonal lines.
The algorithm further considers the locations of lines to obtain a more regular
appearance, and enables the extraction of a level-of-detail representation with
adjustable sparseness of the trajectories along a certain stress direction. To
convey ambiguities in the orientation of the principal stress directions, the
user can select a combined visualization of two principal directions via
oriented ribbons. Additional depth cues improve the perception of the spatial
relationships between trajectories. 3D-TSV is accessible to end users via a
C++- and OpenGL-based rendering frontend that is seamlessly connected to a
MatLab-based extraction backend. The code (BSD license) of 3D-TSV as well as
scripts to make ANSYS and ABAQUS simulation results accessible to the 3D-TSV
backend are publicly available.
