[Netgen] System error during meshing

October 11, 2006, 05:48

I got a very complicated geometry (no warning or error when imported by netgen), which is being meshed by netgen now. The meshing takes at least 2 hours, but still around 99.8%. It shows in the command window that:
"System error: hash table si not fitting for segment: ..."
Does anyone know what's the problem?
Thanks in advance.

hjasak · October 11, 2006, 05:51

sounds like you ran out of memory: this must be a pretty big mesh!

Hrv

October 11, 2006, 06:03

This is the model.

October 11, 2006, 06:06

Here is the model, could anyone try to mesh it?
Thanks

stl.zip

October 11, 2006, 07:53

There are a lot of intersecting elements in your model.

Can you change the settings of you CAD program to get a better stl-file?

Netgen needs a almost perfect geometry to finish meshing.

October 11, 2006, 08:10

Thanks for your answer,Christian.
The original model is downloaded from internet. I just cut one part out, and added a top onto it.
Could you please tell me where do the intersecting elements locate? On the top, bottom,or lateral surface? How to solve it?cad?
Thanks

October 11, 2006, 08:48

They are spread over the hole surface. Use a CAD program. Try to vary the features of the stl-export-function. (more accuracy) What's you CAD program?

October 11, 2006, 09:25

I think i can see them now in netgen. Really a lot. I am not familiar with cad and don't have any cad program in my computer. Are there any other possibilities? Or i have to modify them by hand

Thanks a lot.

October 12, 2006, 04:18

You can try to use the stl-doctor.

Change "Double Click selects:" to "triangle" and select one blue-edged triangle, or Deselect "select with mouse", Insert the number of an intersecting triangle below.

After selecting an intersecting triangle use "move point to middle of trianglepoints". Maybe 0-volume-triangles were generated, delete them. Save the geometry.

Be sure that you exclusively insert the number of an intersecting element. Select an triangle with mouse is not always as easy as it seems.

October 12, 2006, 05:14

Great thanks, Christian. I'll try it.

philippose · October 30, 2006, 14:37

Hi Zhengxiong,
I had a look at your STL file in Netgen, and tried a moderate mesh generation... Here is a screen-shot of the result I got... I have marked in red the areas (there are more on the rear side), where Netgen is having trouble closing the mesh due to inconsistent and intersecting triangles....

As Christian Hausmann suggested, I think you need an STL export with finer triangles defining the surface....

Philippose

philippose · October 30, 2006, 14:40

Oops.... Looks like the file didnt get uploaded... second try :-)

Philippose

philippose · October 30, 2006, 14:45

Looks like Firefox in Linux for some reason doesnt support this possibility of uploading files.... any suggestions from anyone ??

Sorry for flooding the message board :-)!

Philippose

mattijs · October 31, 2006, 13:56

Hi Philippose,

Just a test to see if the uploading works from konqueror. You are aware of the 50k limit?

unitCube.stl

philippose · October 31, 2006, 14:55

Hi,
50k limit :-)!! Oh my... no wonder... its all clear now :-)! The image was 450Kb... but well, with some Gimping and rescaling, I have it down to 12.5Kb... lets see if it works now :-)!

Thanks for pointing out the limit Mattijs :-)!

Philippose

October 11, 2006, 05:48	System error during meshing	#1
ares_tum Guest Posts: n/a	I got a very complicated geometry (no warning or error when imported by netgen), which is being meshed by netgen now. The meshing takes at least 2 hours, but still around 99.8%. It shows in the command window that: "System error: hash table si not fitting for segment: ..." Does anyone know what's the problem? Thanks in advance.

October 11, 2006, 05:51	sounds like you ran out of mem	#2
hjasak Senior Member Hrvoje Jasak Join Date: Mar 2009 Location: London, England Posts: 1,907 Rep Power: 33	sounds like you ran out of memory: this must be a pretty big mesh! Hrv __________________ Hrvoje Jasak Providing commercial FOAM/OpenFOAM and CFD Consulting: http://wikki.co.uk

October 11, 2006, 06:03	This is the model.	#3
ares_tum Guest Posts: n/a	This is the model.

October 11, 2006, 06:06	Here is the model, could anyon	#4
ares_tum Guest Posts: n/a	Here is the model, could anyone try to mesh it? Thanks stl.zip

October 11, 2006, 07:53	There are a lot of intersectin	#5
christian_hausmann Guest Posts: n/a	There are a lot of intersecting elements in your model. Can you change the settings of you CAD program to get a better stl-file? Netgen needs a almost perfect geometry to finish meshing.

October 11, 2006, 08:10	Thanks for your answer,Christi	#6
ares_tum Guest Posts: n/a	Thanks for your answer,Christian. The original model is downloaded from internet. I just cut one part out, and added a top onto it. Could you please tell me where do the intersecting elements locate? On the top, bottom,or lateral surface? How to solve it?cad? Thanks

October 11, 2006, 08:48	They are spread over the hole	#7
christian_hausmann Guest Posts: n/a	They are spread over the hole surface. Use a CAD program. Try to vary the features of the stl-export-function. (more accuracy) What's you CAD program?

October 11, 2006, 09:25	I think i can see them now in	#8
ares_tum Guest Posts: n/a	I think i can see them now in netgen. Really a lot. I am not familiar with cad and don't have any cad program in my computer. Are there any other possibilities? Or i have to modify them by hand Thanks a lot.

October 12, 2006, 04:18	You can try to use the stl-doc	#9
christian_hausmann Guest Posts: n/a	You can try to use the stl-doctor. Change "Double Click selects:" to "triangle" and select one blue-edged triangle, or Deselect "select with mouse", Insert the number of an intersecting triangle below. After selecting an intersecting triangle use "move point to middle of trianglepoints". Maybe 0-volume-triangles were generated, delete them. Save the geometry. Be sure that you exclusively insert the number of an intersecting element. Select an triangle with mouse is not always as easy as it seems.

October 12, 2006, 05:14	Great thanks, Christian. I'll	#10
ares_tum Guest Posts: n/a	Great thanks, Christian. I'll try it.

October 30, 2006, 14:37	Hi Zhengxiong, I had a look	#11
philippose Senior Member Philippose Rajan Join Date: Mar 2009 Location: Germany Posts: 552 Rep Power: 25	Hi Zhengxiong, I had a look at your STL file in Netgen, and tried a moderate mesh generation... Here is a screen-shot of the result I got... I have marked in red the areas (there are more on the rear side), where Netgen is having trouble closing the mesh due to inconsistent and intersecting triangles.... As Christian Hausmann suggested, I think you need an STL export with finer triangles defining the surface.... Philippose

October 30, 2006, 14:40	Oops.... Looks like the file d	#12
philippose Senior Member Philippose Rajan Join Date: Mar 2009 Location: Germany Posts: 552 Rep Power: 25	Oops.... Looks like the file didnt get uploaded... second try :-) Philippose

October 30, 2006, 14:45	Looks like Firefox in Linux fo	#13
philippose Senior Member Philippose Rajan Join Date: Mar 2009 Location: Germany Posts: 552 Rep Power: 25	Looks like Firefox in Linux for some reason doesnt support this possibility of uploading files.... any suggestions from anyone ?? Sorry for flooding the message board :-)! Philippose

October 31, 2006, 13:56	Hi Philippose, Just a test	#14
mattijs Senior Member Mattijs Janssens Join Date: Mar 2009 Posts: 1,419 Rep Power: 26	Hi Philippose, Just a test to see if the uploading works from konqueror. You are aware of the 50k limit? unitCube.stl

October 31, 2006, 14:55	Hi, 50k limit :-)!! Oh my...	#15
philippose Senior Member Philippose Rajan Join Date: Mar 2009 Location: Germany Posts: 552 Rep Power: 25	Hi, 50k limit :-)!! Oh my... no wonder... its all clear now :-)! The image was 450Kb... but well, with some Gimping and rescaling, I have it down to 12.5Kb... lets see if it works now :-)! Thanks for pointing out the limit Mattijs :-)! Philippose

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