isoap: A software for isosurface extraction on arbitrary polyhedra

The implemented algorithm extracts, from discrete data, isosurfaces on arbitrary polyhedra, convex or non-convex, even with non-planar face boundaries. The software package also includes a user manual and routines for writing the geometry of polyhedra and isosurfaces in external files. Tests programs are included to extract isosurfaces on single polyhedral cells and grids of any type, either from implicit mathematical functions or discrete data such as volume fractions or signed distances to scanned surfaces. The proposed method for isosurface extraction on arbitrary polyhedra uses a general polygon tracing procedure, which can be applied to any convex or non-convex geometry, and produces consistent results even for ambiguous situations. The locations of the extracted isosurface points are approximately computed by interpolation. This procedure does not rely on predefined configurations and can be considered as an extension of the marching cubes technique to arbitrary polyhedra. The implemented routines can be used in FORTRAN or C, and, to speed up the operations performed over grids, the OpenMP application programming interface is used. The proposed algorithm can be used in multiple applications, including the visualization of surfaces in computer graphics or the reconstruction of interfaces in PLIC (piecewise linear interface calculation) VOF (volume of fluid) methods.