Tetwild terminating abnormally when background mesh is specified

[dan-lior]

I have a model (model.stl) to mesh and a background mesh (bg.msh) to guide the meshing. I can supply the actual model and mesh, but for now I'll just describe the behaviour.

The background mesh is basically a box that properly contains the model. So far, during the debugging phase, I've been using constant values for the nodal values of the background mesh. I understand that these values specify (or at least suggest) a maximum edge length of the tets). I invoke Tetwild as follows:

./TetWild --input model.stl --bg-mesh bg --output mesh.msh

When I use constant values >= 0.8 for the background mesh, the mesh generated by TetWild seems to work fine.

In particular, for constant values >2.0, the result resembles the mesh generated by Tetwild using default parameters:

./TetWild --input model.stl

This is expected and acceptable , since the model does have some small features.

However, using constant values of 0.6, TetWild crashes after a minute or two with the following message:

"Abnormal program termination: function terminate() was called"

Moreover, meshing with the following command:

./TetWild --input model.stl -a 0.6

succeeds!

Can you explain:
the discrepancy (using a background mesh with constant nodal values of 0.6 and using a prescribed edge length of 0.6 with no background mesh)
How can I get more information on the cause of the abnormal termination? Perhaps the .csv file that TetWild generates with the .msh file?

Thanks,

Dan