We present a method for avoiding cracks in isosurfaces extracted from adaptive mesh refinement (AMR) data. By combining several rectilinear grids of different resolution, AMR methods substantially reduce storage and computation requirements to accurately represent and simulate complicated data and phenomena. AMR data consist of grids of different resolution. As a result discontinuities (''hanging nodes'') arise in dependent field variables at the interfaces of different resolution mesh elements. These discontinuities can result in cracks in isosurfaces extracted for a specific value of a dependent scalar variable. We describe a method for creating transition regions'' between grids of different resolution. These regions are composed of pyramid elements that allow us to avoid crack formation during isosurface extraction.

We describe an adaptive isosurface visualization scheme designed for perspective rendering, taking into account the center of interest and other viewer-specified parameters. To hierarchically decompose a given data domain into a multiresolution data structure, we implement and compare two spatial subdivision data structures: an octree and a recursively defined tetrahedral mesh based on longest-edge bisection. We have implemented our view-dependent isosurface visualization approach using both data structures -- comparing storage requirements, computational efficiency, and visual quality.