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Old   April 1, 2010, 07:35
Default Prism meshing
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Ayyappan.T
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Hi,,
While creating prism mesh from tetra, i got this error

"null dir in move_v_to_levelse, terror in compute_grad, zero lnorm!"

can any one tell what is the issue? and how it can be rectified.

thanks,
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Old   May 26, 2010, 15:23
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We are working to improve these error messages with simple English, problem subsets, etc. If you can supply me this model, I can have development work on a more helpful message. (contact me privately about the file transfer)

In the mean time, I can help a bit...

the "lnorms" of a prism vertex gives the average normal of the attached base
triangles. It also considers the underlying surfaces. This is needed
for computing the marching directions, especially the initial direction. If this is zero, Prism can't determine which direction to march in and therefore must fail.

This failure may be due to projection issues to the geometry. Or lnorm evaluation may fail because no underlying surface is found when a prism node is extruded along a symmetry family. You could check to make sure all shells are in the correct families (those of the underlying surfaces)... There is an option under "Edit Mesh tab => Repair Mesh " to associate mesh with its underlying geometry.

Another option may be that there are conflicting normals. I have seen this happen when two square bars cross within a fluid region. At the 4 corners of the contact patch, there are multiple valid normals. I usually fix this by either modifying the geometry locally or moving the verts slightly off that corner (simply not including those corner points may be enough).

Even if this helps, providing the same case will help improve the software for future users.
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Old   May 28, 2010, 04:52
Default prism meshing
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Thanks for the reply...

I have removed some complexities from the prism meshing and remeshed it and could able to resolve it.

Thanks for the information PSYMN

However sorry to say that the file can not be transfered to you.

reg,
Ayapan.T
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