This paper introduces a technique to properly sample volume boundaries in hardware texture-based Volume Visualization. Prior techniques render a volume with a set of uniformly-spaced proxy geometries that sample (and represent) a set of uniform-depth slices. While this is sufficient for the core of a volume, it does not consider a sample's partial overlap at the boundaries of a volume, and this failing can lead to significant artifacts at these boundaries. Increasing the sampling rate doesn't solve the problem - but the proper calculation will. While these artifacts might not be easily visible with large datasets, this paper expands on the fundamentals of visualization by presenting a correct handling of sampling at boundaries - which is missing from previous literature. Our technique computes the non-unit depth contributions of the volume at the boundaries. We use fragment programs to perform this adaptive border sampling to compute the partial sample contributions and to match sampling-planes at the volume boundaries with the sampling geometry in the core of the volume.
"Adaptive border sampling for hardware texture-based volume visualization", Proc. SPIE 6060, Visualization and Data Analysis 2006, 606005 (16 January 2006); doi: 10.1117/12.643269; https://doi.org/10.1117/12.643269