Meshing an irregular closed surface

Discussion about meshing issues.

Meshing an irregular closed surface

Postby kevin_moerman » Thu Aug 29, 2013 1:38 am

How do I go about meshing a single closed and irregular surface? I am currently trying to mesh the lower part of a femur. So its roughly like a small part of a cylinder morphing into a sphere with a big dent in the middle.

I would upload an STL file to show you an example but uploading STL's is not allowed... after ZIPPING its allowed in principle but the attachments seem limited to 256 KiB which is rather odd given that any model will easily exceed that. You might as well not have an upload attachment feature on this forum...

Thanks,


Kevin
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Re: Meshing an irregular closed surface

Postby csimsoft Moderator » Wed Sep 04, 2013 10:40 am

We have an example of how to mesh a femur head. See attached zip file for model.

#Start Journal File
reset
set node constraint on
#import acis "femoral_head_hex.sat" attributes_on separate_bodies

volume all scale 100
volume all scheme tetmesh
mesh surface all

#tip: export/import file to create a single surface
block 1 surface all
export mesh "junk.g" overwrite
reset
import mesh geometry "junk.g" feature_angle "angle" 0

create brick bounding box volume 1 extended percent 25

volume 2 size 0.2
mesh volume 2

set developer on
hexset hex all separate tri all
create mesh geometry hex in group 4 feature_angle 0

delete volume 2
draw hex all
pillow hex in volume 3 no_smooth
list surface
smooth face in surface 8 scheme laplacian target surface 1

smooth volume all
#volume 3 smooth scheme laplacian
#smooth volume 3
#volume 3 smooth scheme untangle
#smooth volume 3
#volume 3 smooth scheme mean ratio
#smooth volume 3
delete Body 1
draw hex all
#End Journal File

If you have any questions, let us know.

Sorry for the file size limit. We've adjusted it to 25MB per file. Please try uploading your model again.
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Re: Meshing an irregular closed surface

Postby kevin_moerman » Tue Sep 17, 2013 5:34 am

Excellent thanks for your reply and thanks for increasing the upload limit. I got that journal file to work and am also impressed with the hex mesh in principle.

Do you have another example whereby this bone is say surrounded by soft tissue? I would like the surfaces to be smooth and the tissue mesh to share nodes with the bone mesh.

I've uploaded an STL file. Here I want the bones to be voids and am interested in meshing two regions 1) a fat tissue region and 2) a muscle tissue region with shared nodes. Not sure if the single STL as I created here is useful for that but let me know what you think. Any tips on how to approach the above?

Thanks,


Kevin
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Re: Meshing an irregular closed surface

Postby kevin_moerman » Tue Sep 17, 2013 5:53 am

I've been playing with STL files and journal file based meshing. In same cases the solids defined by STL's do not have "bounding curves". This leads to the error:
ERROR: Surface must have bounding curves in order to mesh surface.

Is there a smart and automatic way to add curves or avoid this? I find that say adding curves by cutting and merging the STL surfaces geometry (e.g. using some central planes) sometimes leads to geometric errors or inaccuracies. Any suggestions on this?

Thanks,

Kevin
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Re: Meshing an irregular closed surface

Postby kevin_moerman » Wed Sep 18, 2013 2:21 am

Attached are the split STL files for the skin, muscle-fat and bone boundaries.

Let me know if you require anything else.


Kevin
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