Im2mesh (2D image to triangular meshes)

Convert 2d multi-phase image to finite element meshes, with poly-line simplification feature.

This tool consists of a few functions, e.g., im2mesh, im2Bounds (image to polygonal boundaries), getCtrlPnts (mark intersecting vertex between polygons), simplifyBounds (simplify polygon), poly2mesh (polygon to triangular meshes), printInp (export as Inp file), and printBdf (export as Bdf file).

Features

• Exactly reserve the contact detail between different phases.
• Able to avoid sharp corners when simplifying polyline.
• Support phase selection before meshing (see demo10.m)
• Generated mesh can be exported as inp file (Abaqus), bdf file (Nastran bulk data, compatible with COMSOL), and .node/.ele file.
• 10 examples are presented in demo1.m ~ demo10.m.

Examples

• demo1.m - Demonstrate function im2meshBuiltIn, which use matlab built-in function generateMesh() to generate mesh from geometry.
• demo2.m - Demonstrate function im2mesh, which use MESH2D to generate mesh from geometry.
• demo3.m - Demonstrate how to export mesh as inp, bdf, and .node/.ele file.
• demo4.m - Demonstrate what is inside function im2mesh.
• demo5.m - Demonstrate the case of 'tolerance = eps'.
• demo6.m and demo7.m - Demonstrate parameter 'tolerance'.
• demo8.m - Demonstrate parameter 'tf_avoid_sharp_corner'.
• demo9.m - Demonstrate parameter 'grad_limit'.
• demo10.m - Demonstrate parameter 'select_phase'.

Notes

• Im2mesh program 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.
• You need to do pre-processing to your image before you put the image into Im2mesh program. For example, convert to 8-bit grayscale image, noise removal, and image segmentation (e.g., Otsu's method). What Im2mesh needs is a segmented grayscale image. For those fellows who don't have any experience in digital image processing, please refer to the following information: https://www.mathworks.com/matlabcentral/fileexchange/71772-im2mesh-2d-image-to-triangular-meshes?tab=discussions#discussions_1692673
• To make demo2.m~demo10.m run, you need to download MESH2D from https://www.mathworks.com/matlabcentral/fileexchange/25555-mesh2d-delaunay-based-unstructured-mesh-generation, and add the folder (mesh2d-master) to your path. After that, you can start with demo2.m~demo10.m in im2mesh. Check images in the folder (im2mesh\images\...).

If you have any questions or suggestions, feel free to send me an email.

[e-mail], Jan 2023.

Acknowledgments

Great thanks Dr. Yang Lu providing valuable advice on this tool.