Output Formats

Output Formats#

cad_to_dagmc can create three types of output files for neutronics simulations.

Output Types#

Format

Description

Use Case

DAGMC H5M

Triangular surface mesh

Geometry for particle transport

Unstructured VTK

Tetrahedral volume mesh

Mesh tallies in OpenMC

GMSH Mesh

GMSH native format

Debugging, further processing

Conformal Meshes

Combined surface + volume

When you need both

Quick Comparison#

Feature

DAGMC H5M

Unstructured VTK

GMSH Mesh

Surface mesh

Yes

No

Yes (2D)

Volume mesh

No

Yes

Yes (3D)

For geometry

Yes

No

Intermediate

For tallies

No

Yes

No

File extension

.h5m

.vtk

.msh

Basic Export Pattern#

import cadquery as cq
from cad_to_dagmc import CadToDagmc

# Create geometry
assembly = cq.Assembly()
assembly.add(cq.Workplane("XY").sphere(10), name="sphere")

# Initialize model
model = CadToDagmc()
model.add_cadquery_object(assembly, material_tags=["tungsten"])

# Export to different formats
model.export_dagmc_h5m_file(filename="dagmc.h5m")           # Surface mesh
model.export_unstructured_mesh_file(filename="umesh.vtk")    # Volume mesh
model.export_gmsh_mesh_file(filename="mesh.msh")             # GMSH format

Choosing an Output Format#

Use DAGMC H5M when:

  • Running DAGMC-enabled transport (OpenMC, MCNP, FLUKA)

  • You need geometry definition for particle tracking

  • Surface mesh is sufficient

Use Unstructured VTK when:

  • Creating mesh tallies in OpenMC

  • Need volumetric mesh for post-processing

  • Doing CFD coupling

Use GMSH Mesh when:

  • Debugging mesh quality

  • Using GMSH visualization (Gmsh GUI)

  • Further mesh processing needed

Use Conformal Meshes when:

  • Running both transport and mesh tallies

  • Surface and volume mesh boundaries must match exactly

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