Merge pull request #1150 from pshriwise/uwuw

UWUW Workflow for DAGMC

docs/source/io_formats/settings.rst

@@ -88,6 +88,14 @@ you care. This element has the following attributes/sub-elements:
 
     *Default*: 0.0
 
+--------------------------------
+``<dagmc>`` Element
+--------------------------------
+
+When the DAGMC mode is enabled, the OpenMC geometry will be read from the file
+``dagmc.h5m``. If a :ref:`geometry.xml <io_geometry>` file is present with
+``dagmc`` set to ``true``, it will be ignored.
+
 --------------------------------
 ``<electron_treatment>`` Element
 --------------------------------

docs/source/usersguide/geometry.rst

@@ -398,3 +398,32 @@ if needed, lattices, the last step is to create an instance of
 
 .. _constructive solid geometry: http://en.wikipedia.org/wiki/Constructive_solid_geometry
 .. _quadratic surfaces: http://en.wikipedia.org/wiki/Quadric
+
+--------------------------
+Using CAD-based Geometry
+--------------------------
+
+OpenMC relies on the Direct Accelerated Geometry Monte Carlo toolkit (`DAGMC
+<https://svalinn.github.io/DAGMC/>`_) to represent CAD-based geometry in a
+surface mesh format. A DAGMC run can be enabled in OpenMC by setting the
+``dagmc`` property to ``True`` in the model Settings either via the Python
+:class:`openmc.settings` Python class::
+
+  settings = openmc.Settings()
+  settings.dagmc = True
+
+or in the :ref:`settings.xml <io_settings>` file::
+
+  <dagmc>true</dagmc>
+
+With ``dagmc`` set to true, OpenMC will load the DAGMC model (from a local file
+named ``dagmc.h5m``) when initializing a simulation. If a `geometry.xml
+<../io_formats/geometry.html>`_ is present as well, it will be ignored.
+
+  **Note:** DAGMC geometries used in OpenMC are currently required to be clean,
+  meaning that all surfaces have been `imprinted and merged
+  <https://svalinn.github.io/DAGMC/usersguide/trelis_workflow.html>`_
+  successfully and that the model is `watertight
+  <https://svalinn.github.io/DAGMC/usersguide/tools.html#make-watertight>`_. Future
+  implementations of DAGMC geometry will support small volume overlaps and
+  un-merged surfaces.

docs/source/usersguide/install.rst

@@ -159,14 +159,25 @@ Prerequisites
           sudo apt install mpich libmpich-dev
           sudo apt install openmpi-bin libopenmpi-dev
 
+    * DAGMC_ toolkit for simulation using CAD-based geometries
+
+      OpenMC supports particle tracking in CAD-based geometries via the Direct
+      Accelerated Geometry Monte Carlo (DAGMC) toolkit (`installation
+      instructions
+      <https://svalinn.github.io/DAGMC/install/dag_multiple.html>`_). For use in
+      OpenMC, only the ``MOAB_DIR`` and ``BUILD_TALLY`` variables need to be
+      specified in the CMake configuration step.
+    |
     * git_ version control software for obtaining source code
 
+
 .. _gfortran: http://gcc.gnu.org/wiki/GFortran
 .. _gcc: https://gcc.gnu.org/
 .. _CMake: http://www.cmake.org
 .. _OpenMPI: http://www.open-mpi.org
 .. _MPICH: http://www.mpich.org
 .. _HDF5: https://www.hdfgroup.org/solutions/hdf5/
+.. _DAGMC: https://svalinn.github.io/DAGMC/index.html
 
 Obtaining the Source
 --------------------
@@ -236,6 +247,12 @@ openmp
   Enables shared-memory parallelism using the OpenMP API. The Fortran compiler
   being used must support OpenMP. (Default: on)
 
+dagmc
+  Enables use of CAD-based DAGMC_ geometries. Please see the note about DAGMC in
+  the optional dependencies list for more information on this feature. The
+  installation directory for DAGMC should also be defined as `DAGMC_ROOT` in the
+  CMake configuration command. (Default: off)
+
 coverage
   Compile and link code instrumented for coverage analysis. This is typically
   used in conjunction with gcov_.