[Gmsh] Binary image meshing

Sathyanarayan Rao sathyanarayan.rao at uclouvain.be
Mon Feb 26 16:58:20 CET 2018

Hello gmsh team,

I was thinking of elegant way to mesh an binary image ( black and white). Is there simple way to define black and white regions as separate physical surfaces

in gmsh and automatically assign mesh size field ( finer for white , coarser for black ) ?  I saw one example where one of the author of gmsh meshes his own

image and it is very interesting to see this but in his code, is there a way to mark different regions of color with physical marker, for example all dark regions

where finer mesh occurs as one physical marker based on pixel value of image ?


// Merge the image (this will create a new post-processing view,
// View[0])
Merge "cg.jpg";

// Modify the normalized pixel values to make them reasonnable
// characteristic lengths for the mesh
Plugin(ModifyComponents).Expression0 = "v0 * 10";

// Apply the view as the current background mesh
Background Mesh View[0];

// Build a simple geometry on top of the background mesh
w = View[0].MaxX;
h = View[0].MaxY;
Line(1) = {1,2};
Line(2) = {2,3};
Line(3) = {3,4};
Line(4) = {4,1};
Line Loop(5) = {3,4,1,2};
Plane Surface(6) = {5};

Best Regards,

Sathyanarayan Rao, PhD student
Earth and Life Institute/Environmental Sciences (ELI-e)
Université catholique de Louvain
c.037, Croix du Sud 2, Louvain-la-Neuve, Belgium
Phone: 010473827 ( intercom 73827)

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