  Spectral datasets obtained at radio frequencies and optical/IR wavelengths
are increasing in complexity as new facilities and instruments come online,
resulting in an increased need to visualize and quantitatively analyze the
velocity structures. As the visible structure in spectral data cubes is not
purely spatial, additional insight is required to relate structures in 2D space
plus line-of-sight velocity to their true three-dimensional (3D) structures.
This can be achieved through the use of models that are converted to
velocity-space representations. We have used the S2PLOT programming library to
enable intuitive, interactive comparison between 3D models and spectral data,
with potential for improved understanding of the spatial configurations. We
also report on the use of 3D Cartesian shapelets to support quantitative
analysis.
