I am new and recently started to play with OpenMesh. I would like to subdivide a triangle mesh based on midpoint criteria. It is required that the subdivided mesh has the same geometry as the original one. No geometry loss!

I read a STL mesh and tried to use the uniform subdivider:

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struct CustomTraits : public OpenMesh::DefaultTraitsDouble { };
typedef OpenMesh::TriMesh_ArrayKernelT<CustomTraits> OM_TriMesh;

OM_TriMesh om_mesh;

OpenMesh::IO::read_mesh( om_mesh, fname_in);

int n_refine = 1;

OpenMesh::Subdivider::Uniform::MidpointT<OM_TriMesh> divider;
divider.attach(om_mesh);
divider(n_refine);

divider.detach();

OpenMesh::IO::write_mesh( om_mesh  , fname_out);

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Conceptually, I supposed it would uniformly divide one triangle into four triangles after connecting its edge midpoints. However, I found it was not true and the subdivided mesh is geometrically not exactly the same as the original one.

In addition, for a simple mesh with only 1 triangle(stl format), I found that only the central triangle connected with midpoints is generated and triangles associated with the original vertices are lost. I looked at the source code, and found that it was caused by the "if (!_m.is_boundary(vh))" check. So it seems the boundary vertices are ignored. Then the geometry after subdivision became different from the original mesh. Is it true? Can anyone help and tell me how to do that? Thank you very much.

Best,

Xujun