Im2mesh (2D image to finite element mesh)

Generate finite element mesh based on 2D multi-phase image. For image-based finite element analysis.

GUI version: Im2mesh_GUI

Standalone desktop application: Installer (No need to install MATLAB)

Tutorial: Im2mesh_GUI Tutorial.pdf

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 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

• Version 2.45 can export polygonal boundaries extracted from image as dxf file (CAD).
• Function plotMeshes become more powerful, providing a few plot style settings (see demo08).
• Version 2.2.0 supports using 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 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)
• stl file
• MATLAB PDE model object
• For other formats (such as vtk), you can import the generated msh file into software Gmsh and then export.

How to start

After downloading Im2mesh package, 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 (demo1.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, msh, and stl 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 hmax and grad_limit in mesh generation
• demo08 - Function plotMeshes
• demo09 - How to select phases for meshing
• demo10 - Different polyline smoothing techniques
• demo11 - Find node sets at the interface and boundary
• demo12 - Function pixelMesh (pixel-based quadrilateral mesh)
• demo13 - 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

Notes

Im2mesh package identifies different phases in a image by their grayscales. Different grayscales correspond to different phases. If you have 4 level of grayscales in a image, the resulted meshes will contain 4 phases.

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