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Extrude mesh with different thickness over different regions

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Message 1 of 3
yisong668
1305 Views, 2 Replies

Extrude mesh with different thickness over different regions

Hello,

I tried to use the "Extrude" function in Meshmixer to generate the vessel walls with different thickness. The purple colored region is supposed to extrude for 0.25 mm to generate the vein wall and the white region for 0.5 mm as the artery wall. However, when I use "extrude" for each individual surface, I only see the extruded offset surface and the original surface seems to be overwritten. This problem does not occur if I extrude the whole region with uniform thickness. What should I do in order to generate different wall thicknesses over different regions? The goal is to generate the stl geometry of the vessel walls and then exported to ICEM for meshing (which will be used for later simulations). Thanks in advance for the help.

MESHMIXER.PNG

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Message 2 of 3
MagWeb
in reply to: yisong668

I assume your source mesh describes the interior surface of the vessels.

Next I think your source mesh owns an open boundary on each end (as in my last image 0).

If you do an extrusion on a mesh region where one side owns a neighbour surface and the other end an open boundary MM runs in a non manifold issue at the neighbour side. If it keeps the non selected part + the selection + the extrusion result it would generate a situation where three surfaces share the same boundary. This isn't allowed in general.

Ohne Titel.jpeg

Now you could extrude the whole object at 0.25mm in a first go. Select and extrude the part you want to have thicker in a second go (0.25 +0.25 = 0.5)... 

But Extrude isn't the proper tool. Use Offset instead. This tool "extrudes" along normals by default, tries to get rid of possible self intersections and allows a smooth transition (extruded/non-extruded):

1. SelectAll and run Edit/Offset: Set the lower thickness (here 0.25) and enable Connected and PreserveGroups (just for easier selection in the next step)

2. Now there's a watertight object. Select the thicker region by double clicking the group. Important:  Use the UnwrapBrush mode. Against the default SphereBrush (selecting all inside a sphere) this mode selects the first surface only (for it is a wrapping disk ).

3. Again run Edit/Offset to add the missing thickness on that region(at Connected and maybe PreserveGroups if you're interested in keeping the group). Optional: Set some SoftTransition (the transition happens inside the selection).

 

Ohne Titel.jpeg



Gunter Weber
Triangle Artisan

Message 3 of 3
yisong668
in reply to: MagWeb

Thank you so much for the detailed help!!

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