CadQuery Backend

CadQuery Backend#

The CadQuery backend uses CadQuery’s built-in tessellation for direct meshing. This is simpler but provides less control than GMSH.

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"])

model.export_dagmc_h5m_file(
    filename="dagmc.h5m",
    meshing_backend="cadquery",
    tolerance=0.1,
    angular_tolerance=0.1,
)

Parameters#

Parameter

Type

Default

Description

tolerance

float

0.1

Linear tolerance for tessellation

angular_tolerance

float

0.1

Angular tolerance for tessellation

Tolerance explanation:

  • Lower tolerance = finer mesh = more triangles

  • tolerance controls how far the mesh can deviate from the true surface (linear distance)

  • angular_tolerance controls the maximum angle between adjacent facet normals

Advantages#

Advantage

Explanation

Fewer triangles on flat surfaces

CadQuery’s tessellation optimizes flat regions

Simpler

Only 2 parameters to tune

No GMSH dependency

Uses built-in CadQuery tessellation

Can be faster

For simple geometries with flat surfaces

Limitations#

Limitation

Impact

No volume meshing

Cannot use export_unstructured_mesh_file()

No per-volume sizing

set_size parameter is ignored

No mesh algorithms

Only one tessellation method

Less control

Only tolerance parameters available

Warning

When using meshing_backend="cadquery", the following parameters are ignored and a warning is raised:

  • min_mesh_size

  • max_mesh_size

  • set_size

  • mesh_algorithm

When to Use CadQuery Backend#

Good for:

  • Simple geometries

  • Models with many flat surfaces (boxes, plates)

  • When you want the smallest possible mesh

  • Surface mesh only (no volume mesh needed)

  • Minimizing dependencies

Not suitable for:

  • When you need volume meshes

  • When you need per-volume mesh sizing

  • Complex curved geometries requiring fine control

Comparison Example#

The same geometry can produce different mesh sizes:

import cadquery as cq
from cad_to_dagmc import CadToDagmc

# Create a simple box (lots of flat surfaces)
box = cq.Workplane("XY").box(10, 10, 10)
assembly = cq.Assembly()
assembly.add(box)

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

# GMSH backend - may produce more triangles on flat surfaces
model.export_dagmc_h5m_file(
    filename="dagmc_gmsh.h5m",
    meshing_backend="gmsh",
    min_mesh_size=1.0,
    max_mesh_size=5.0,
)

# CadQuery backend - optimizes flat surfaces
model.export_dagmc_h5m_file(
    filename="dagmc_cq.h5m",
    meshing_backend="cadquery",
    tolerance=0.5,
)

For a simple box, CadQuery will use just 12 triangles (2 per face), while GMSH may create more based on the mesh size parameters.

See Also#

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