⚠️ This library is in development. Expect breaking changes and bugs, and feel welcome to contribute.

⚠️ Use MOAB version <= 5.3.1. Later versions suffer from undocumented transport errors in DAGMC.

⚠️ See logging to enable logging output when using Jupyter.

Stellarmesh is a Gmsh wrapper and DAGMC geometry creator for fusion neutronics workflows, building on other libraries such as cad-to-dagmc and cad-to-openmc. The goal is to reach feature parity with the Cubit plugin to enable a fully-featured and open-source workflow.

Progress:

• Import of CadQuery, build123d, STEP and BREP geometry
• Correct implementation of surface-sense
• Imprinting and merging of conformal geometry
• Mesh refinement
• Automated testing and integration
• Programatic manipulation of .h5m tags e.g. materials

Contents

• Contents
• Installation
• Usage
  • Geometry construction
  • Examples
    • Simple torus geometry
    • Other
  • Logging
  • Mesh refinement
• Comparison to other libraries

Installation

pip install stellarmesh

or install the development version with:

pip install https://github.com/Thea-Energy/stellarmesh.git

Note: Stellarmesh requires an installation of MOAB with pymoab, which is not available on PyPi and must be installed either from source or using Conda.

Usage

Geometry construction

Stellarmesh supports both build123d (recommended) and CadQuery for geometry construction but does not depend on either.

The included examples use build123d. To install, run:

pip install git+https://github.com/gumyr/build123d

For documentation and usage examples, see Read the Docs.

Examples

Simple torus geometry

import build123d as bd
import stellarmesh as sm

solids = [bd.Solid.make_torus(1000, 100)]
for _ in range(3):
    solids.append(solids[-1].faces()[0].thicken(100))
solids = solids[1:]

geometry = sm.Geometry(solids, material_names=["a", "a", "c"])
mesh = sm.Mesh.from_geometry(geometry, min_mesh_size=50, max_mesh_size=50)
mesh.write("test.msh")
mesh.render("doc/torus-mesh-reversed.png", rotation_xyz=(90, 0, -90), normals=15)

h5m = sm.MOABModel.from_mesh(mesh)
h5m.write("dagmc.h5m")
h5m.write("dagmc.vtk")

Rendered mesh with normals.

Check overlaps

❯ overlap_check dagmc.h5m

NOTICE:
     Performing overlap check using triangle vertex locations only.
     Use the '-p' option to check more points on the triangle edges.
     Run '$ overlap_check --help' for more information.

Running overlap check:
100% |===============================================================>|+
No overlaps were found.

Check materials

❯ mbsize -ll dagmc.h5m | grep mat:

NAME = mat:a
NAME = mat:c

Check watertight

❯ check_watertight dagmc.h5m

number of surfaces=4
number of volumes=3

0/0 (nan%) unmatched edges
0/4 (0%) unsealed surfaces
0/3 (0%) unsealed volumes
leaky surface ids=
leaky volume ids=
0.173068 seconds

Other

• Mesh refinement
• Stellarmesh logo
• Imprinted boxes

Logging

Stellarmesh uses the logging library for debug, info and warning messages. Set the level with:

import logging

logging.basicConfig() # Required in Jupyter to correctly set output stream
logging.getLogger("stellarmesh").setLevel(logging.INFO)

Mesh refinement

Note: given CAD geometry, Gmsh often produces high-quality meshes that do not benefit from remeshing.

Stellarmesh supports mesh refinement using the mmg library. Refine a mesh with:

refined_mesh = mesh.refine(
  ...
)

and consult the Mesh.refine and mmgs documentations for parameter values.

The refined mesh has more triangles in regions with high curvature thanks to the hausdorff parameter.

Many thanks to Erik B. Knudsen for his work on remeshing for CAD-to-OpenMC.

Comparison to other libraries

	Stellarmesh	CAD-to-DAGMC	CAD-to-OpenMC	Cubit
Developer	Thea Energy	Jonathan Shimwell	Erik B. Knudsen	Coreform
Meshing backend	Gmsh	Gmsh	Gmsh/CQ	Cubit
In development	✓	✓	✓	✓
Open-source	✓	✓	✓
Surface-sense handling	✓	✓	1	✓
Mesh refinement	✓		✓	✓
Manipulation of .h5m files	2

Note: Please file an issue if this table is out-of-date.

¹ In development on a personal branch

² In development