Im2mesh (2D image to finite element mesh)

Im2mesh is an open-source MATLAB/Octave package for generating finite element mesh based on 2D segmented multi-phase image. It provides a robust workflow capable of processing various input images, such as microstructure images of engineering materials. Due to its generalized framework, Im2mesh can handle segmented image with more than 10 phases. Im2mesh was originally released on MathWorks File Exchange in 2019.

Im2mesh can also be used as a mesh generation interface for MATLAB 2D multi-part geometry, aka multi-domain or multi-phase geometry (see demo14-17).

   

News:

• In version 2.42, function plotMeshes become more powerful, providing a few plot style settings.
• Version 2.2.0 can use Gmsh as mesh generator (unstructured quadrilateral mesh).
• Version 2.1.6 updates the DOI. Im2mesh is now citable.

Features:

• Accurately preserve the contact details between different phases.
• Incorporates polyline smoothing and simplification
• Able to avoid sharp corners when simplifying polylines.
• Able to edit polygonal boundary before mesh generation.
• Support phase selection and local mesh refinement.
• 4 mesh generators are available for selection: MESH2D, generateMesh, Gmsh, and pixelMesh.
• Graphical user interface (GUI) version is available as a MATLAB app and as a standalone desktop application.

Generated mesh can be exported as:

• inp file with boundary node set (Abaqus)
• bdf file (Nastran bulk data, compatible with COMSOL),
• msh file (Gmsh mesh format)
• MATLAB PDE model object
• For other formats (such as stl and vtk), you can import the generated msh file into software Gmsh and then export.

Dependencies

• When using Im2mesh package or Im2mesh_GUI in MATLAB, you need to install MATLAB and the following MATLAB toolboxes: Image Processing Toolbox, Mapping Toolbox.
• When using Im2mesh_GUI as a standalone desktop application, there is no need to install MATLAB or any MATLAB toolboxes. You can download the installer for standalone desktop app from: link

Version compatibility

• Im2mesh_GUI: MATLAB R2017b or later; version higher than R2018b is preferred.
• Im2mesh package: MATLAB R2017b or later. GNU Octave 9.3.0 or later.
• Gmsh: tested with version 4.13.1.

How to start

After downloading Im2mesh package (releases), I suggest you start with Im2mesh_GUI app in the folder, which will help you understand the workflow and parameters of Im2mesh. A detailed tutorial is provided in Im2mesh_GUI Tutorial.pdf.

Then, you can learn to use Im2mesh package in the folder "Im2mesh_Matlab" or "Im2mesh_Octave". 16 examples are provided.

• If you're using MATLAB, examples are live script mlx files (demo01.mlx ~ demo18.mlx). If you find some text in the mlx file is missing, please read the html file instead. Note that demo02.mlx requires MATLAB Partial Differential Equation (PDE) Toolbox. If you don't have PDE Toolbox, you can skip demo02.mlx.
• If you're using Octave, examples are m files (demo01.m ~ demo10.m).
• Examples are also available as html files in the folder "demo_html".

Examples:

• demo01 - Demonstrate function im2mesh, which use MESH2D as mesh generator.
• demo02 - Demonstrate function im2meshBuiltIn, which use MATLAB built-in function generateMesh as mesh generator.
• demo03 - Export: save mesh as inp, bdf, and msh file; save geometry as geo file or PSLG data.
• demo04 - What is inside im2mesh
• demo05 - Avoid sharp corner
• demo06 - Thresholds in polyline smoothing
• demo07 - Parameter grad_limit in mesh generation
• demo08 - Parameter hmax in mesh generation
• demo09 - How to select phases for meshing
• demo10 - Different polyline smoothing techniques
• demo11 - Find node sets at the interface and boundary
• demo12 - Demonstrate function pixelMesh (pixel-based quadrilateral mesh)
• demo13 - How to use Gmsh as mesh generator
• demo14 - Use polyshape to define geometry for mesh generation
• demo15 - Edit polygonal boundaries before meshing
• demo16 - Add mesh seeds/nodes
• demo17 - Refine mesh
• demo18 - Create tetrahedral mesh based on 2d image

Cite as

If you use Im2mesh, please cite it as follows.

Ma, Jiexian, & Li, Yuanyuan (2025). Im2mesh: A MATLAB/Octave package for generating finite element mesh based on 2D multi-phase image (2.1.5). Zenodo. https://doi.org/10.5281/zenodo.14847059

Once my paper is published, I will update a new DOI here.

Acknowledgments

Many thanks to Dr. Yang Lu for providing valuable suggestions and testing of export formats.

This project incorporates code from the following open-source projects. I appreciate the contributions of the original authors. Each incorporated code retains its original copyright.

• MESH2D by Darren Engwirda
• dpsimplify by Wolfgang Schwanghart
• p_poly_dist by Michael Yoshpe
• MeshQualityQuads by Allan Peter Engsig-Karup
• ccma by UniBwTAS

Other related projects

• voxelMesh (voxel-based finite element mesh)
• writeMesh (write mesh to inp, bdf, and msh files)