diff --git a/docs/source/devguide/workflow.rst b/docs/source/devguide/workflow.rst
index a53bd114b..7a303f45e 100644
--- a/docs/source/devguide/workflow.rst
+++ b/docs/source/devguide/workflow.rst
@@ -37,9 +37,8 @@ In order to be considered suitable for inclusion in the *develop* branch, the
 following criteria must be satisfied for all proposed changes:
 
 - Changes have a clear purpose and are useful.
-- Compiles under all conditions (MPI, OpenMP, HDF5, etc.).  This is checked as
-  part of the test suite.
-- Passes the regression suite.
+- Compiles and passes the regression suite with all configurations (This is
+  checked by Travis CI).
 - If appropriate, test cases are added to regression suite.
 - No memory leaks (checked with valgrind_).
 - Conforms to the OpenMC `style guide`_.
@@ -81,8 +80,7 @@ features and bug fixes. The general steps for contributing are as follows:
 
    At a minimum, you should describe what the changes you've made are and why
    you are making them. If the changes are related to an oustanding issue, make
-   sure it is cross-referenced. A wise developer would also check whether their
-   changes do indeed pass the regression test suite.
+   sure it is cross-referenced.
 
 5. A trusted developer will review your pull request based on the criteria
    above. Any issues with the pull request can be discussed directly on the pull
@@ -104,7 +102,7 @@ full OpenMC code is executed. Results from simulations are compared with
 expected results. The test suite is comprised of many build configurations
 (e.g. debug, mpi, hdf5) and the actual tests which reside in sub-directories
 in the tests directory. We recommend to developers to test their branches
-before submitting a formal pull request using gfortran and intel compilers
+before submitting a formal pull request using gfortran and Intel compilers
 if available.
 
 The test suite is designed to integrate with cmake using ctest_.
@@ -113,9 +111,9 @@ download these cross sections please do the following:
 
 .. code-block:: sh
 
-    cd ../data
-    python get_nndc_data.py
-    export CROSS_SECTIONS=<path_to_data_folder>/nndc/cross_sections.xml
+    cd ../scripts
+    ./openmc-get-nndc-data
+    export OPENMC_CROSS_SECTIONS=<path_to_data_folder>/nndc_hdf5/cross_sections.xml
 
 The test suite can be run on an already existing build using:
 
@@ -137,21 +135,29 @@ more control over which tests are executed.
 Before running the test suite python script, the following environmental
 variables should be set if the default paths are incorrect:
 
-    * **FC** - The command of the Fortran compiler (e.g. gfotran, ifort).
+    * **FC** - The command for a Fortran compiler (e.g. gfotran, ifort).
 
         * Default - *gfortran*
 
+    * **CC** - The command for a C compiler (e.g. gcc, icc).
+
+        * Default - *gcc*
+
+    * **CXX** - The command for a C++ compiler (e.g. g++, icpc).
+
+        * Default - *g++*
+
     * **MPI_DIR** - The path to the MPI directory.
 
-        * Default - */opt/mpich/3.1.3-gnu*
+        * Default - */opt/mpich/3.2-gnu*
 
     * **HDF5_DIR** - The path to the HDF5 directory.
 
-        * Default - */opt/hdf5/1.8.14-gnu*
+        * Default - */opt/hdf5/1.8.16-gnu*
 
     * **PHDF5_DIR** - The path to the parallel HDF5 directory.
 
-        * Default - */opt/phdf5/1.8.14-gnu*
+        * Default - */opt/phdf5/1.8.16-gnu*
 
 To run the full test suite, the following command can be executed in the
 tests directory:
@@ -192,15 +198,12 @@ a test you need to add the following files to your new test directory,
 *test_name* for example:
 
     * OpenMC input XML files
-    * **test_name.py** - python test driver script, please refer to other
+    * **test_name.py** - Python test driver script, please refer to other
       tests to see how to construct. Any output files that are generated
       during testing must be removed at the end of this script.
-    * **results.py** - python script that extracts results from statepoint
-      output files. By default it should look for a binary file, but can
-      take an argument to overwrite which statepoint file is processed,
-      whether it is at a different batch or with an HDF5 extension. This
-      script must output a results file that is named *results_test.dat*.
-      It is recommended that any real numbers reported use *12.6E* format.
+    * **inputs_true.dat** - ASCII file that contains Python API-generated XML
+      files concatenated together. When the test is run, inputs that are
+      generated are compared to this file.
     * **results_true.dat** - ASCII file that contains the expected results
       from the test. The file *results_test.dat* is compared to this file
       during the execution of the python test driver script. When the
diff --git a/docs/source/methods/cross_sections.rst b/docs/source/methods/cross_sections.rst
index b9043a944..9f677bac4 100644
--- a/docs/source/methods/cross_sections.rst
+++ b/docs/source/methods/cross_sections.rst
@@ -183,45 +183,43 @@ Multi-Group Data
 
 The data governing the interaction of particles with various nuclei or materials
 are represented using a multi-group library format specific to the OpenMC code.
-The format is described in the :ref:`mgxs_lib_spec`.
-The data itself can be prepared via traditional paths or directly from a
-continuous-energy OpenMC calculation by use of the Python API as is shown in the
-:ref:`notebook_mgxs_part_iv` example notebook. This multi-group
-library consists of meta-data (such as the energy group structure) and multiple
-`xsdata` objects which contains the required microscopic or macroscopic
-multi-group data.
+The format is described in the :ref:`mgxs_lib_spec`. The data itself can be
+prepared via traditional paths or directly from a continuous-energy OpenMC
+calculation by use of the Python API as is shown in the
+:ref:`notebook_mg_mode_part_i` example notebook. This multi-group library
+consists of meta-data (such as the energy group structure) and multiple `xsdata`
+objects which contains the required microscopic or macroscopic multi-group data.
 
 At a minimum, the library must contain the absorption cross section
 (:math:`\sigma_{a,g}`) and a scattering matrix. If the problem is an eigenvalue
-problem then all fissionable materials must also contain either
-a fission production matrix cross section
-(:math:`\nu\sigma_{f,g\rightarrow g'}`), or
-both the fission spectrum data (:math:`\chi_{g'}`) and a fission production
-cross section (:math:`\nu\sigma_{f,g}`), or, .  The library must also contain
-the fission cross section (:math:`\sigma_{f,g}`) or the fission energy release
-cross section (:math:`\kappa\sigma_{f,g}`) if the associated tallies are
-required by the model using the library.
+problem then all fissionable materials must also contain either a fission
+production matrix cross section (:math:`\nu\sigma_{f,g\rightarrow g'}`), or both
+the fission spectrum data (:math:`\chi_{g'}`) and a fission production cross
+section (:math:`\nu\sigma_{f,g}`), or, .  The library must also contain the
+fission cross section (:math:`\sigma_{f,g}`) or the fission energy release cross
+section (:math:`\kappa\sigma_{f,g}`) if the associated tallies are required by
+the model using the library.
 
 After a scattering collision, the outgoing particle experiences a change in both
 energy and angle. The probability of a particle resulting in a given outgoing
-energy group (`g'`) given a certain incoming energy group (`g`) is provided
-by the scattering matrix data.  The angular information can be expressed either
-via Legendre expansion of the particle's change-in-angle (:math:`\mu`), a
-tabular representation of the probability distribution function of :math:`\mu`,
-or a histogram representation of the same PDF. The formats used to
-represent these are described in the :ref:`mgxs_lib_spec`.
+energy group (`g'`) given a certain incoming energy group (`g`) is provided by
+the scattering matrix data.  The angular information can be expressed either via
+Legendre expansion of the particle's change-in-angle (:math:`\mu`), a tabular
+representation of the probability distribution function of :math:`\mu`, or a
+histogram representation of the same PDF. The formats used to represent these
+are described in the :ref:`mgxs_lib_spec`.
 
 Unlike the continuous-energy mode, the multi-group mode does not explicitly
 track particles produced from scattering multiplication (i.e., :math:`(n,xn)`)
 reactions.  These are instead accounted for by adjusting the weight of the
 particle after the collision such that the correct total weight is maintained.
 The weight adjustment factor is optionally provided by the `multiplicity` data
-which is required to be provided in the form of a group-wise matrix.
-This data is provided as a group-wise matrix since the probability of producing
-multiple particles in a scattering reaction depends on both the incoming energy,
-`g`, and the sampled outgoing energy, `g'`. This data represents the average
-number of particles emitted from a scattering reaction, given a scattering
-reaction has occurred:
+which is required to be provided in the form of a group-wise matrix.  This data
+is provided as a group-wise matrix since the probability of producing multiple
+particles in a scattering reaction depends on both the incoming energy, `g`, and
+the sampled outgoing energy, `g'`. This data represents the average number of
+particles emitted from a scattering reaction, given a scattering reaction has
+occurred:
 
 .. math::
 
diff --git a/docs/source/pythonapi/index.rst b/docs/source/pythonapi/index.rst
index 0345ec32b..004d3809a 100644
--- a/docs/source/pythonapi/index.rst
+++ b/docs/source/pythonapi/index.rst
@@ -135,6 +135,7 @@ Constructing Tallies
    openmc.EnergyFunctionFilter
    openmc.Mesh
    openmc.Trigger
+   openmc.TallyDerivative
    openmc.Tally
    openmc.Tallies
 
@@ -483,6 +484,28 @@ Functions
     openmc.data.endf.get_tab2_record
     openmc.data.endf.get_text_record
 
+---------------------------------------------------------
+:mod:`openmc.openmoc_compatible` -- OpenMOC Compatibility
+---------------------------------------------------------
+
+.. autosummary::
+    :toctree: generated
+    :nosignatures:
+    :template: myfunction.rst
+
+    openmc.openmoc_compatible.get_openmoc_material
+    openmc.openmoc_compatible.get_openmc_material
+    openmc.openmoc_compatible.get_openmoc_surface
+    openmc.openmoc_compatible.get_openmc_surface
+    openmc.openmoc_compatible.get_openmoc_cell
+    openmc.openmoc_compatible.get_openmc_cell
+    openmc.openmoc_compatible.get_openmoc_universe
+    openmc.openmoc_compatible.get_openmc_universe
+    openmc.openmoc_compatible.get_openmoc_lattice
+    openmc.openmoc_compatible.get_openmc_lattice
+    openmc.openmoc_compatible.get_openmoc_geometry
+    openmc.openmoc_compatible.get_openmc_geometry
+
 .. _Jupyter: https://jupyter.org/
 .. _NumPy: http://www.numpy.org/
 .. _Codecademy: https://www.codecademy.com/tracks/python
diff --git a/docs/source/pythonapi/openmoc_compatible.rst b/docs/source/pythonapi/openmoc_compatible.rst
deleted file mode 100644
index bf353b96e..000000000
--- a/docs/source/pythonapi/openmoc_compatible.rst
+++ /dev/null
@@ -1,8 +0,0 @@
-.. _pythonapi_openmoc_compatible:
-
-=====================
-OpenMOC Compatibility
-=====================
-
-.. automodule:: openmc.openmoc_compatible
-    :members:
diff --git a/docs/source/usersguide/input.rst b/docs/source/usersguide/input.rst
index b8629f180..e1775d364 100644
--- a/docs/source/usersguide/input.rst
+++ b/docs/source/usersguide/input.rst
@@ -87,6 +87,22 @@ be validated using the following command:
 
    /opt/openmc/bin/openmc-validate-xml
 
+--------------
+Physical Units
+--------------
+
+Unless specified otherwise, all length quantities are assumed to be in units of
+centimeters, all energy quantities are assumed to be in electronvolts, and all
+time quantities are assumed to be in seconds.
+
+======= ============ ======
+Measure Default unit Symbol
+======= ============ ======
+length  centimeter   cm
+energy  electronvolt eV
+time    second       s
+======= ============ ======
+
 --------------------------------------
 Settings Specification -- settings.xml
 --------------------------------------
diff --git a/openmc/__init__.py b/openmc/__init__.py
index 2f65d0317..d8e7e2482 100644
--- a/openmc/__init__.py
+++ b/openmc/__init__.py
@@ -1,5 +1,3 @@
-import warnings
-
 from openmc.arithmetic import *
 from openmc.cell import *
 from openmc.mesh import *
diff --git a/openmc/cell.py b/openmc/cell.py
index b578702bb..9993175ef 100644
--- a/openmc/cell.py
+++ b/openmc/cell.py
@@ -289,9 +289,10 @@ class Cell(object):
         c3, s3 = cos(phi), sin(phi)
         c2, s2 = cos(theta), sin(theta)
         c1, s1 = cos(psi), sin(psi)
-        return np.array([[c1*c2, c1*s2*s3 - c3*s1, s1*s3 + c1*c3*s2],
-                         [c2*s1, c1*c3 + s1*s2*s3, c3*s1*s2 - c1*s3],
-                         [-s2, c2*s3, c2*c3]])
+        self._rotation_matrix = np.array([
+            [c1*c2, c1*s2*s3 - c3*s1, s1*s3 + c1*c3*s2],
+            [c2*s1, c1*c3 + s1*s2*s3, c3*s1*s2 - c1*s3],
+            [-s2, c2*s3, c2*c3]])
 
     @translation.setter
     def translation(self, translation):
diff --git a/openmc/geometry.py b/openmc/geometry.py
index 02bcbe180..598aa4312 100644
--- a/openmc/geometry.py
+++ b/openmc/geometry.py
@@ -361,18 +361,25 @@ class Geometry(object):
         if not case_sensitive:
             name = name.lower()
 
-        all_cells = self.get_all_cells().values()
         cells = set()
 
-        for cell in all_cells:
-            cell_fill_name = cell.fill.name
-            if not case_sensitive:
-                cell_fill_name = cell_fill_name.lower()
+        for cell in self.get_all_cells().values():
+            names = []
+            if cell.fill_type in ('material', 'universe', 'lattice'):
+                names.append(cell.fill.name)
+            elif cell.fill_type == 'distribmat':
+                for mat in cell.fill:
+                    if mat is not None:
+                        names.append(mat.name)
 
-            if cell_fill_name == name:
-                cells.add(cell)
-            elif not matching and name in cell_fill_name:
-                cells.add(cell)
+            for fill_name in names:
+                if not case_sensitive:
+                    fill_name = fill_name.lower()
+
+                if fill_name == name:
+                    cells.add(cell)
+                elif not matching and name in fill_name:
+                    cells.add(cell)
 
         cells = list(cells)
         cells.sort(key=lambda x: x.id)
diff --git a/openmc/material.py b/openmc/material.py
index 92d992a6f..357753fa9 100644
--- a/openmc/material.py
+++ b/openmc/material.py
@@ -980,7 +980,7 @@ class Materials(cv.CheckedList):
         :envvar:`OPENMC_CROSS_SECTIONS` environment variable will be used for
         continuous-energy calculations and
         :envvar:`OPENMC_MG_CROSS_SECTIONS` will be used for multi-group
-        calculations to find the path to the XML cross section file.
+        calculations to find the path to the HDF5 cross section file.
     multipole_library : str
         Indicates the path to a directory containing a windowed multipole
         cross section library. If it is not set, the
diff --git a/openmc/plots.py b/openmc/plots.py
index 2ba5d9758..cc2fcc4b6 100644
--- a/openmc/plots.py
+++ b/openmc/plots.py
@@ -636,7 +636,8 @@ class Plot(object):
             subelement.text = ' '.join(str(x) for x in color)
 
         if self._colors:
-            for domain, color in self._colors.items():
+            for domain, color in sorted(self._colors.items(),
+                                        key=lambda x: x[0].id):
                 subelement = ET.SubElement(element, "color")
                 subelement.set("id", str(domain.id))
                 if isinstance(color, string_types):
diff --git a/openmc/stats/multivariate.py b/openmc/stats/multivariate.py
index ca25cf5fb..0ab11b7c5 100644
--- a/openmc/stats/multivariate.py
+++ b/openmc/stats/multivariate.py
@@ -54,7 +54,8 @@ class PolarAzimuthal(UnitSphere):
     """Angular distribution represented by polar and azimuthal angles
 
     This distribution allows one to specify the distribution of the cosine of
-    the polar angle and the azimuthal angle independently of once another.
+    the polar angle and the azimuthal angle independently of one another. The
+    polar angle is measured relative to the reference angle.
 
     Parameters
     ----------
diff --git a/openmc/tally_derivative.py b/openmc/tally_derivative.py
index 1c8a316cf..185e7ab6a 100644
--- a/openmc/tally_derivative.py
+++ b/openmc/tally_derivative.py
@@ -23,24 +23,24 @@ class TallyDerivative(EqualityMixin):
 
     Parameters
     ----------
-    derivative_id : Integral, optional
+    derivative_id : int, optional
         Unique identifier for the tally derivative. If none is specified, an
         identifier will automatically be assigned
     variable : str, optional
         Accepted values are 'density', 'nuclide_density', and 'temperature'
-    material : Integral, optional
-        The perturubed material ID
+    material : int, optional
+        The perturbed material ID
     nuclide : str, optional
         The perturbed nuclide. Only needed for 'nuclide_density' derivatives.
         Ex: 'Xe135'
 
     Attributes
     ----------
-    id : Integral
+    id : int
         Unique identifier for the tally derivative
     variable : str
         Accepted values are 'density', 'nuclide_density', and 'temperature'
-    material : Integral
+    material : int
         The perturubed material ID
     nuclide : str
         The perturbed nuclide. Only needed for 'nuclide_density' derivatives.
diff --git a/openmc/volume.py b/openmc/volume.py
index c9e1a5afa..6c4b130f9 100644
--- a/openmc/volume.py
+++ b/openmc/volume.py
@@ -246,9 +246,9 @@ class VolumeCalculation(object):
         results = type(self).from_hdf5(filename)
 
         # Make sure properties match
-        assert self.domains == results.domains
-        assert self.lower_left == results.lower_left
-        assert self.upper_right == results.upper_right
+        assert self.ids == results.ids
+        assert np.all(self.lower_left == results.lower_left)
+        assert np.all(self.upper_right == results.upper_right)
 
         # Copy results
         self.volumes = results.volumes
diff --git a/scripts/openmc-voxel-to-silovtk b/scripts/openmc-voxel-to-silovtk
index 471047127..9748cc3bb 100755
--- a/scripts/openmc-voxel-to-silovtk
+++ b/scripts/openmc-voxel-to-silovtk
@@ -3,30 +3,24 @@
 from __future__ import division, print_function
 import struct
 import sys
+from argparse import ArgumentParser
 
 import numpy as np
 import h5py
 
-def parse_options():
-    """Process command line arguments"""
 
-    from optparse import OptionParser
-    usage = r"""%prog [options] <voxel_file>"""
-    p = OptionParser(usage=usage)
-    p.add_option('-o', '--output', action='store', dest='output',
-                 default='plot', help='Path to output SILO or VTK file.')
-    p.add_option('-v', '--vtk', action='store_true', dest='vtk',
-                 default=False, help='Flag to convert to VTK instead of SILO.')
-    parsed = p.parse_args()
-    if not parsed[1]:
-        p.print_help()
-        return parsed
-    return parsed
+def main():
+    # Process command line arguments
+    parser = ArgumentParser()
+    parser.add_argument('voxel_file', help='Path to voxel file')
+    parser.add_argument('-o', '--output', action='store',
+                        default='plot', help='Path to output SILO or VTK file.')
+    parser.add_argument('-s', '--silo', action='store_true',
+                        default=False, help='Flag to convert to SILO instead of VTK.')
+    args = parser.parse_args()
 
-
-def main(filename, o):
     # Read data from voxel file
-    fh = h5py.File(filename, 'r')
+    fh = h5py.File(args.voxel_file, 'r')
     dimension = fh.attrs['num_voxels']
     width = fh.attrs['voxel_width']
     lower_left = fh.attrs['lower_left']
@@ -35,14 +29,8 @@ def main(filename, o):
     nx, ny, nz = dimension
     upper_right = lower_left + width*dimension
 
-    if o.vtk:
-        try:
-            import vtk
-        except:
-            print('The vtk python bindings do not appear to be installed '
-                  'properly.\nOn Ubuntu: sudo apt install python-vtk\n'
-                  'See: http://www.vtk.org/')
-            return
+    if not args.silo:
+        import vtk
 
         grid = vtk.vtkImageData()
         grid.SetDimensions(nx+1, ny+1, nz+1)
@@ -53,12 +41,12 @@ def main(filename, o):
         data.SetName("id")
         data.SetNumberOfTuples(nx*ny*nz)
         for x in range(nx):
-            sys.stdout.write(" {0}%\r".format(int(x/nx*100)))
+            sys.stdout.write(" {}%\r".format(int(x/nx*100)))
             sys.stdout.flush()
             for y in range(ny):
                 for z in range(nz):
                     i = z*nx*ny + y*nx + x
-                    data.SetValue(i, voxel_data[x,y,z])
+                    data.SetValue(i, voxel_data[x, y, z])
         grid.GetCellData().AddArray(data)
 
         writer = vtk.vtkXMLImageDataWriter()
@@ -66,31 +54,27 @@ def main(filename, o):
             writer.SetInputData(grid)
         else:
             writer.SetInput(grid)
-        if not o.output.endswith(".vti"):
-            o.output += ".vti"
-        writer.SetFileName(o.output)
+        if not args.output.endswith(".vti"):
+            args.output += ".vti"
+        writer.SetFileName(args.output)
         writer.Write()
 
     else:
-        try:
-            import silomesh
-        except:
-            print('The silomesh package does not appear to be installed '
-                  'properly.\nSee: https://github.com/nhorelik/silomesh/')
-            return
-        if not o.output.endswith(".silo"):
-            o.output += ".silo"
-        silomesh.init_silo(o.output)
+        import silomesh
+
+        if not args.output.endswith(".silo"):
+            args.output += ".silo"
+        silomesh.init_silo(args.output)
         meshparams = list(map(int, dimension)) + list(map(float, lower_left)) + \
                      list(map(float, upper_right))
         silomesh.init_mesh('plot', *meshparams)
         silomesh.init_var("id")
         for x in range(nx):
-            sys.stdout.write(" {0}%\r".format(int(x/nx*100)))
+            sys.stdout.write(" {}%\r".format(int(x/nx*100)))
             sys.stdout.flush()
             for y in range(ny):
                 for z in range(nz):
-                    silomesh.set_value(float(voxel_data[x,y,z]),
+                    silomesh.set_value(float(voxel_data[x, y, z]),
                                        x + 1, y + 1, z + 1)
         print()
         silomesh.finalize_var()
@@ -99,6 +83,4 @@ def main(filename, o):
 
 
 if __name__ == '__main__':
-    (options, args) = parse_options()
-    if args:
-        main(args[0], options)
+    main()
diff --git a/tests/run_tests.py b/tests/run_tests.py
index 28bedab0d..f0ecd8291 100755
--- a/tests/run_tests.py
+++ b/tests/run_tests.py
@@ -43,6 +43,7 @@ parser.add_option("-s", "--script", action="store_true", dest="script",
 # Default compiler paths
 FC='gfortran'
 CC='gcc'
+CXX='g++'
 MPI_DIR='/opt/mpich/3.2-gnu'
 HDF5_DIR='/opt/hdf5/1.8.16-gnu'
 PHDF5_DIR='/opt/phdf5/1.8.16-gnu'
@@ -55,6 +56,8 @@ if 'FC' in os.environ:
     FC = os.environ['FC']
 if 'CC' in os.environ:
     CC = os.environ['CC']
+if 'CXX' in os.environ:
+    CXX = os.environ['CXX']
 if 'MPI_DIR' in os.environ:
     MPI_DIR = os.environ['MPI_DIR']
 if 'HDF5_DIR' in os.environ:
@@ -162,9 +165,11 @@ class Test(object):
             else:
                 self.fc = os.path.join(MPI_DIR, 'bin', 'mpif90')
             self.cc = os.path.join(MPI_DIR, 'bin', 'mpicc')
+            self.cxx = os.path.join(MPI_DIR, 'bin', 'mpicxx')
         else:
             self.fc = FC
             self.cc = CC
+            self.cxx = CXX
 
     # Sets the build name that will show up on the CDash
     def get_build_name(self):
@@ -195,6 +200,7 @@ class Test(object):
     def run_ctest_script(self):
         os.environ['FC'] = self.fc
         os.environ['CC'] = self.cc
+        os.environ['CXX'] = self.cxx
         if self.mpi:
             os.environ['MPI_DIR'] = MPI_DIR
         if self.phdf5:
@@ -210,6 +216,7 @@ class Test(object):
     def run_cmake(self):
         os.environ['FC'] = self.fc
         os.environ['CC'] = self.cc
+        os.environ['CXX'] = self.cxx
         if self.mpi:
             os.environ['MPI_DIR'] = MPI_DIR
         if self.phdf5: