Meshing Backends

cad_to_dagmc supports three meshing backends for creating surface and volume meshes.

Available Backends

Backend	Description	Best For
GMSH	Full-featured meshing library	Complex models, fine mesh control
CadQuery	Built-in CadQuery tessellation	Simple models, flat surfaces
cad-to-dagmc-mesher	Purpose-built surface and tetrahedral mesher	Surface and volume meshes without GMSH

Quick Comparison

Feature	GMSH	CadQuery	cad-to-dagmc-mesher
Surface mesh (h5m)	Yes	Yes	Yes
Volume mesh (vtk)	Yes	No	Yes
Mesh size control	Full (min/max/per-volume)	Limited (tolerance only)	Tolerances + target_edge_length
Mesh algorithms	10 algorithms	1 (built-in)	1 (built-in)
Parallel meshing	Yes	Partial	Yes (DAG scheduler)
Dependencies	Requires GMSH	Built into CadQuery	Installed with cad_to_dagmc
Flat surface efficiency	Standard	Better (fewer triangles)	Better (fewer triangles)

Choosing a Backend

Use GMSH backend when:

• You need precise control over mesh density

• You want per-volume mesh sizing with set_size

• You need parallel meshing for large models

• You need specific mesh algorithms

Use CadQuery backend when:

• You only need surface meshes

• You want simpler configuration

• Your geometry has many flat surfaces (fewer triangles)

• Your geometry is straightforward

Use cad-to-dagmc-mesher backend (the default) when:

• You need volume meshes for unstructured mesh tallies without GMSH

• You want the surface (h5m) and volume (vtk) meshes from a single meshing call

• You want simple configuration (tolerances plus one tetrahedron edge length)

A call that gives no backend and no backend-specific arguments uses cad-to-dagmc-mesher. It is installed with the pip package but is not on conda-forge, so a conda installation without it falls back to CadQuery.

Basic Usage

import cadquery as cq
from cad_to_dagmc import CadToDagmc

assembly = cq.Assembly()
assembly.add(cq.Workplane("XY").sphere(10))

model = CadToDagmc()
model.add_cadquery_object(assembly, material_tags=["mat1"])

# GMSH backend
model.export_dagmc_h5m_file(
    filename="dagmc_gmsh.h5m",
    meshing_backend="gmsh",
    min_mesh_size=0.5,
    max_mesh_size=10.0,
)

# CadQuery backend
model.export_dagmc_h5m_file(
    filename="dagmc_cq.h5m",
    meshing_backend="cadquery",
    tolerance=0.1,
    angular_tolerance=0.1,
)

# cad-to-dagmc-mesher backend
model.export_dagmc_h5m_file(
    filename="dagmc_mesher.h5m",
    meshing_backend="cad-to-dagmc-mesher",
    tolerance=0.01,
    angular_tolerance=0.2,
)

Mesh Sizing Overview

For detailed per-volume mesh sizing, see Mesh Sizing.