  When employing Direct Volume Rendering (DVR) for visualizing volumetric
scalar fields, classification is generally performed on a piecewise constant or
piecewise linear approximation of the field on a viewing ray. Smoothed Particle
Hydrodynamics (SPH) data sets define volumetric scalar fields as the sum of
individual particle contributions, at highly varying spatial resolution. We
present an approach for approximating SPH scalar fields along viewing rays with
piece-wise polynomial functions of higher order. This is done by approximating
each particle contribution individually and then efficiently summing the
results, thus generating a higher-order representation of the field with a
resolution adapting to the data resolution in the volume.
