NaN normals when writing mesh object to stl file about meshmagick

[ahmedmetin]

It happens when there duplicate vertices it seems.
facet normal nan nan nan
outer loop
vertex 0.000000e+00 0.000000e+00 -2.144183e+00
vertex 0.000000e+00 0.000000e+00 -2.144183e+00
vertex -5.000000e-01 8.660254e-01 -2.144183e+00
endloop
endfacet

which cause 0 normal vector.

Then there is
n = np.cross(v1 - v0, v2 - v0)
n /= np.linalg.norm(n)

in write_STL function, which causes the problem I think.
Is there a way to eliminate the duplicate vertices in meshmagick?

[frongere]

From what I can see on your last post, the triangle you show seems to be collapsed. Two of its vertices are at the same position so the triangle does not represent a plane but a line. You get NaN for the normal as it is undefined...
Maybe you could preprocess the mesh by using the -hm option to attempt to heal the mesh.

[kmacolini]

Hi @ahmedmetin
Did you resolve this issue? I am having the same problem currently. I tried to preprocess with heal_normals(), but I did not notice any changes in the resulting .stl file. I might be doing something wrong. Thank you. @frongere