Adaptive mesh refinement (AMR) is a numerical simulation technique used in
computational fluid dynamics (CFD). By using a set
of nested grids of different resolutions, AMR combines the simplicity of structured
rectilinear grids with the possibility to adapt to local changes in complexity in the
domain. Without proper interpolation on the boundaries of grids of different levels
of a hierarchy, discontinuities can arise. Treating locations of data values given
at cell centers of AMR grids as vertices of a dual grid creates gaps between
hierarchy levels. Using an index-based tessellation approach that fills these gaps with
``stitch cells'' we define an interpolation scheme that avoids discontinuities at
level boundaries. We use the resulting interpolation scheme to generate volume-rendered
images. Modifying transfer functions on a per-level basis
allows us to emphasize (or de-emphasize) a specific level and gain a better
understanding of the underlying hierarchical structure.
