THIS PROJECT IS NO LONGER SUPPORTED

This project relies on the iGeom interface to provide access to an underlying CAD engine. That interface is no longer actively supported in any project and none of this historical implementations continue to be valid due to licensing and other restrictions.

Since 2024, support for importing MCNP geometries into Cubit has been incorporated natively into Coreform Cubit. Users are directed to explore Coreform Cubit as a solution. The verison of Cubit distributed by Sandia National Laboratories does not yet include this support. Users of Sandia Cubit are encouraged to request this capability through their Sandia points of contact.

In theory, it should be possible to revive this by providing access to an open source CAD engine, such as OpenCascade (OCC), either by implementing a lightweight version of iGeom for OCC or modifying this code to directly access OCC. The permissive license of this should allow others to tackle this if/when they have interest.

Below is the original README file describing other aspects of this package.

MCNP2CAD README

MCNP to iGeom/CAD converter: a program to extract the geomtery from MCNP input files and write it out using any ITAPS iGeom backend.

This project creates a shared object file which is called by the Trelis plugin or the command line interface created with the -DBUILD_CLI=true flag.

The following groups intend to support such implementations:

• CNERG will develop an iGeom-like interface as part of a Trelis & Cubit plugin that uses this library to import MCNP geometry into Trelis/Cubit.
• The SIGMA team will develop an iGeom-like interface as part of an implementation of CGM that is based on the OpenCascade solid modeling engine. This version may support a command line tool.

Bug reports are appreciated - please post an issue in our Github repository.

This tool is based on an concept first developed at Argonne National Laboratory.

Build Instructions:

Using cmake:

Install Eigen3.

When installing mcnp2cad, be sure to include the following flags:

-DIGEOM_LIB_DIR= path to directory containing libigeom

-DIGEOM_INCLUDE_DIR= path to iGeom include directory

If building the command line interface, also include the following flag:

-DBUILD_CLI=yes

Unsupported Features:

• Could be added easily:

  • More direct control over the size of the sphere/graveyard in which the geometry sits
  • Support for interpolation (nI/nILOG) and multiplication (nM) syntax.
  • Make the title card optional, as it apparently is in MCNP.

• Could be added with effort:

  • Correct handling of hexagonal prism lattices for lattices based on irregular hexgons
  • Support for ELL (ellipse), WED (wedge), and ARB (arbitrary polyhedron) macrobodies
  • Ability to refer to individual facets of macrobodies as surfaces in cell specification, using the NNNN.MM syntax. Parsing support for this feature exists, but output support does not.
  • Support for lattices in universe 0
  • Faster/more efficient generation of embedded universes within lattices.
  • Complete support for M=-1 argument in TRn (transform) cards.
  • Automatically annotate reflecting/white boundaries and periodic surfaces.
  • Support for 3-arg and 5-arg specification of rotations in transformations.
  • Support for jump (nJ) syntax: requires knowledge of default values in many possible contexts

• Could be added with substantial effort:

  • General support for SQ, GQ, X, Y, and Z surfaces. (Elliptic Cylinders and Elliptic Cones currently supported.) (Simple X, Y, Z surfaces are already supported.)
  • Robust error detection and reporting for ill-formed MCNP inputs.