  Visualization of large vector line data is a core task in geographic and
cartographic systems. Vector maps are often displayed at different cartographic
generalization levels, traditionally by using several discrete levels-of-detail
(LODs). This limits the generalization levels to a fixed and predefined set of
LODs, and generally does not support smooth LOD transitions. However, fast GPUs
and novel line rendering techniques can be exploited to integrate dynamic
vector map LOD management into GPU-based algorithms for locally-adaptive line
simplification and real-time rendering. We propose a new technique that
interactively visualizes large line vector datasets at variable LODs. It is
based on the Douglas-Peucker line simplification principle, generating an
exhaustive set of line segments whose specific subsets represent the lines at
any variable LOD. At run time, an appropriate and view-dependent error metric
supports screen-space adaptive LOD levels and the display of the correct subset
of line segments accordingly. Our implementation shows that we can simplify and
display large line datasets interactively. We can successfully apply line style
patterns, dynamic LOD selection lenses, and anti-aliasing techniques to our
line rendering.
