Geometry Input Methods

There are at least four ways to input geometries into SIMION:

  1. Create the potential array (PA) file using the Modify function (Chapter 5), which is SIMION’s 3D GUI paint utility.
  2. Create the PA file using a GEM Geometry File (Appendix I of SIMION 8 manual or Appendix J of SIMION 7 manual), in which constructive solid geometry (CSG) primitives are described in an ASCII text file. GEM files are often created by hand though can also be created with the graphical Virtual Device utility. GEM files can also contain STL files (as of
  3. Create the PA file from a 2D/3D CAD model (Converting from 3D CAD (STL) Format to PA Format), 2D raster (bitmap) (SL Tools Tutorial) image, or ASCII data file using the SL Tools.
  4. Create the PA file from a programming language via the SL Libraries or your own code or (in SIMION 8.1) the simion.pas interface inside SIMION.

Method #1 is useful for simpler things or to manually edit a PA file created by the other methods. It’s easiest to use for things that have cylindrical or 2D planar symmetry (i.e. surfaces of revolution or projections of 2D images) but can be used for 3D asymmetric geometries as well with a little more practice.

Method #2-4 are useful for somewhat more complicated geometries, geometries defined more mathematically, or if you need to parameterize your model (e.g. accurately rescale or quickly change dimensions on your model for testing). See SIMION Example: geometry_optimize for an example of running a system over many parameterizations of a geometry, which GEM handles well (this would typically be more difficult to automate using a CAD package unless perhaps you used certain APIs in your CAD package from your SIMION user program).

Method #3-4 are useful if your model already exists in another format, whether a complex solid drawn in a third-party CAD package or a field defined in a text file or other format.

Method #3 (and Method #4 if using the SL Libraries) require SIMION® 8.0 (or SL Toolkit for SIMION 7). Method #2 can optionally be done with Virtual Device.

Only GEM files (as of 8.1.1), STL files (as of officially) and the Lua API support Electrode Surface Enhancement / Fractional Grid Units. supports integrated STL and GEM files, allowing these two powerful approaches to be mixed and matched.


This page is abridged from the full SIMION "Supplemental Documentation" (Help file). The following additional sections can be found in the full version of this page accessible via the "Help > Supplemental Documentation" menu in SIMION 8.1.1 or above:
  • Notes on Modify