CAD to DAGMC

A package that converts CAD geometry to DAGMC h5m files, unstructured mesh files (VTK), and Gmsh (msh) files ready for use in neutronics simulations.

Workflow

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flowchart LR
    subgraph inputs [" "]
        direction TB
        CQ(["  CadQuery  "])
        STEP(["  STEP files  "])
        GMSH_IN(["  GMSH mesh  "])
        CQ ~~~ STEP ~~~ GMSH_IN
    end

    subgraph tagging [" "]
        TAG{"  Material  <br/>  Tagging  "}
    end

    subgraph meshing [" "]
        direction TB
        GMSH_E["  GMSH  "]
        CQ_E["  CadQuery  "]
    end

    subgraph h5m_backend [" "]
        direction TB
        H5PY(("  h5py  "))
        MOAB(("  pymoab  "))
    end

    subgraph outputs [" "]
        direction TB
        H5M[["  DAGMC h5m  "]]
        VTK[["  Unstructured VTK  "]]
        MSH[["  GMSH mesh  "]]
    end

    CQ & STEP & GMSH_IN --> TAG

    TAG --> GMSH_E & CQ_E

    GMSH_E & CQ_E --> H5PY & MOAB
    H5PY & MOAB --> H5M

    GMSH_E --> VTK & MSH

    style inputs fill:none,stroke:none
    style tagging fill:none,stroke:none
    style meshing fill:none,stroke:none
    style outputs fill:none,stroke:none
    style h5m_backend fill:none,stroke:none

    style CQ fill:#e0f2fe,stroke:#0284c7,stroke-width:1.5px,color:#0c4a6e
    style STEP fill:#e0f2fe,stroke:#0284c7,stroke-width:1.5px,color:#0c4a6e
    style GMSH_IN fill:#e0f2fe,stroke:#0284c7,stroke-width:1.5px,color:#0c4a6e

    style TAG fill:#fef3c7,stroke:#d97706,stroke-width:1.5px,color:#78350f

    style GMSH_E fill:#f3e8ff,stroke:#9333ea,stroke-width:1.5px,color:#581c87
    style CQ_E fill:#f3e8ff,stroke:#9333ea,stroke-width:1.5px,color:#581c87

    style H5PY fill:#fce7f3,stroke:#db2777,stroke-width:1.5px,color:#831843
    style MOAB fill:#fce7f3,stroke:#db2777,stroke-width:1.5px,color:#831843

    style H5M fill:#dcfce7,stroke:#16a34a,stroke-width:1.5px,color:#14532d
    style VTK fill:#dcfce7,stroke:#16a34a,stroke-width:1.5px,color:#14532d
    style MSH fill:#dcfce7,stroke:#16a34a,stroke-width:1.5px,color:#14532d
    

Inputs Tagging Meshing H5M Backend Outputs

Key Features

Multiple Input Formats	Flexible Material Tagging
- CadQuery objects - STEP files - GMSH mesh files	- Manual tags - Assembly names - CadQuery Materials - GMSH physical groups
Two Meshing Backends	Multiple Output Formats
- GMSH (full control, volume meshing) - CadQuery (simpler, direct)	- DAGMC h5m (surface mesh) - Unstructured VTK (volume mesh) - GMSH files
Two H5M Backends	Advanced Options
- h5py (default, no MOAB needed) - pymoab (official MOAB)	- Per-volume mesh sizing - Geometry scaling - Parallel meshing

Getting Started

• Installation
  • Install using pip
  • Install using Conda
  • Optional: Installing pymoab
  • Optional: Installing OpenMC
• Quickstart
  • Basic Example
  • From a STEP File
  • Creating a Volume Mesh
  • Creating Conformal Surface and Volume Meshes
  • Using in OpenMC

Inputs

• Input Sources
  • Basic Pattern
• CadQuery Objects
  • Supported Object Types
  • Basic Example
  • Multiple Objects
  • Using Compounds
  • Using Assemblies
  • API Reference
  • See Also
• CadQuery Assemblies
  • Basic Assembly
  • Using Assembly Names as Material Tags
  • Using Assembly Materials as Tags
  • Assemblies with Mesh Parameters
  • Nested Assemblies
  • Assembly Tagging Options Comparison
  • See Also
• STEP Files
  • Single STEP File
  • Using Assembly Names from STEP Files
  • Using Assembly Materials from STEP Files
  • Multiple STEP Files
  • Mixing STEP Files with CadQuery Objects
  • Scaling STEP Files
  • API Reference
  • Tips
  • See Also
• GMSH Files
  • From GMSH File with Manual Tags
  • From GMSH File with Physical Groups
  • Using assembly-mesh-plugin
  • From GMSH Object in Memory
  • Complete OpenMC Workflow
  • API Reference
  • See Also

Material Tagging

• Material Tagging
  • Tagging Methods
  • Quick Comparison
  • How Tags Are Stored
  • Tag Name Guidelines
• Manual Material Tags
  • Basic Usage
  • Single Volume
  • Multiple Volumes with Same Material
  • With STEP Files
  • Reserved Tag Names
  • Multiple Additions
  • Determining Volume Count
  • Using Tags with set_size
  • Error Handling
  • See Also
• Assembly Names as Material Tags
  • Basic Usage
  • Why Use Assembly Names?
  • Using Names with Mesh Sizing
  • Unnamed Parts
  • Naming Conventions
  • Using Colors for Visualization
  • See Also
• Assembly Materials as Tags
  • Basic Usage
  • When to Use Assembly Materials
  • Example: Names vs Materials
  • Multiple Parts, Same Material
  • Requirements and Errors
  • Comparison with Assembly Names
  • See Also
• GMSH Physical Groups
  • How It Works
  • Basic Usage
  • Complete Example with OpenMC
  • Using assembly-mesh-plugin
  • Overriding Physical Groups
  • Creating Physical Groups in GMSH
  • Checking Physical Groups
  • Requirements
  • See Also

Outputs

• Output Formats
  • Output Types
  • Quick Comparison
  • Basic Export Pattern
  • Choosing an Output Format
• DAGMC H5M Files
  • Basic Export
  • With Different Backends
  • With Meshing Backends
  • API Reference
  • Using in OpenMC
  • See Also
• Unstructured Mesh VTK Files
  • Basic Export
  • Complex Geometry Example
  • Selecting Specific Volumes
  • API Reference
  • Using in OpenMC
  • Complete OpenMC Workflow
  • See Also
• GMSH Mesh Files
  • Basic Export
  • With Per-Volume Mesh Sizing
  • API Reference
  • Use Cases
  • See Also
• Conformal Meshes
  • Why Conformal Meshes?
  • Basic Usage
  • Selecting Volumes for Volume Mesh
  • Complete Example with OpenMC
  • How It Works
  • API Notes
  • See Also

Meshing

• Meshing Backends
  • Available Backends
  • Quick Comparison
  • Choosing a Backend
  • Basic Usage
  • Mesh Sizing Overview
• GMSH Backend
  • Basic Usage
  • Mesh Size Parameters
  • Mesh Algorithms
  • Per-Volume Mesh Sizing
  • CAD Transfer Method
  • Advanced GMSH Options
  • Volume Meshing
  • Parameters Reference
  • See Also
• CadQuery Backend
  • Basic Usage
  • Parameters
  • Advantages
  • Limitations
  • When to Use CadQuery Backend
  • Comparison Example
  • See Also
• Per-Volume Mesh Sizing
  • Basic Usage
  • Specifying Volumes
  • How It Works
  • Complete Example
  • Using with Volume Meshes
  • Tips
  • See Also

Advanced

• Advanced Options
  • Topics
  • Quick Reference
• Geometry Scaling
  • Basic Usage
  • Scaling at Different Stages
  • Common Scale Factors
  • Different Scales for Different Parts
  • Neutronics Unit Conventions
  • Mesh Size and Scaling
  • See Also
• Imprinting
  • What is Imprinting?
  • Default Behavior
  • Disabling Imprinting
  • When to Disable Imprinting
  • Performance Considerations
  • Imprinting and Material Tag Order
  • Example: Adjacent Boxes
  • See Also
• Implicit Complement
  • What is the Implicit Complement?
  • Basic Usage
  • Using in OpenMC
  • With GMSH Files
  • Common Use Cases
  • When to Use
  • See Also
• Parallel Processing
  • When to Limit Threads
  • Limiting CadQuery Threads
  • Limiting GMSH Threads
  • Thread Options Summary
  • Complete Example
  • Performance Considerations
  • See Also
• H5M File Backends
  • h5py Backend (Default)
  • pymoab Backend
  • Installing pymoab
  • Error Handling
  • Comparing Backends
  • File Compatibility
  • Comparison Table
  • See Also

Reference

• Python API Reference
  • Main Class
  • Standalone Functions
  • Exceptions