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"Point in Polyhedron" transforms .obj files into DDSCAT7 shape format (readable by ADDA).

Authors: Roman Schuh and Thomas Wriedt, using routines by John Burkardt. Later changes by ADDA contributors.

To compile run make in current directory. 64-bit Windows executable is available in the corresponding ADDA package.

Usage:

pip [<grid> [<filename>]]

Executable is named pip, it accepts up tp two command line parameters:

  • <grid> - maximum shape size (number of dipoles) along the largest dimension that is determined automatically. If omitted, the default value of 80 is used (and further arguments cannot be used).
  • <filename>. Input shape is read from <filename>.obj and DDSCAT7 shape is saved into <filename>.dat. If omitted, PIP will use the default filename shape (read shape.obj and save shape.dat). If <filename> includes extension, then it will be used for input file (instead of .obj).

It should be possible to read other 3D formats, which are supported by routines in ivread_wr.f90 - see comments in the source files. However, only .obj format is sufficiently tested. Also limited testing has been performed for .dxf, .stl, and .wrl formats. Multiple materials in input files (at least, for .obj and .wrl formats) are transformed into multiple domains in the output file. Should work for very large number of dipoles (limited only by memory and computational time).

Existing limitations:

  • For poorly tested input formats, it is potentially possible that the materials will not be properly recognized, leading to too much materials and errors in voxelization. Then there is a backup option to produce single-domain output file. For that change the value of logical, parameter :: ignore_mat in FEM-Geo-Wr.f90 to .true..
  • By default, the code supports only triangular and quadrilateral faces. However, support for polygons of higher order can be added by changing the line integer, parameter :: face_order_max = 4 in FEM-Geo-Wr.f90 and recompiling.
  • The algorithm requires consistent alignment of face normals (more specifically, order of vertices in each face) - they should all point outward. This is usually automatically satisfied by modern 3D editors.

To test executable run pip 20 in the current folder. It will use provided shape.obj that defines a star-shaped object and produce shape.dat which should be identical to provided shape_test.dat.

The reference for this tool is: R. Schuh, "Arbitrary particle shape modeling in DDSCAT and validation of simulation results", in T. Wriedt & A. G. Hoekstra (Editors): Proceedings of the DDA - Workshop, Institut fur Werkstofftechnik, Bremen (23 March 2007), p.22-24.