Element of very distorted form is found.

[abidshahriar]

I am getting this following error while try to run the simulation:

“3D Analysis Element of very distorted form is found! External elemen number = 294 Internal element number = 294 “

[germknoedlspeck]

Hi @abidshahriar,

this is likely due to your object geometry containing a triangular element whose edges have largely varying length. You can check (and thus, correct) which element this is by using

grep 294 ../ObjectMeshes/Reference/Elements.txt

in the cmd line. If you are not on a Linux machine, you may scroll manually to element #294 in the text file or apply the equivalent command in a Windows console. With this, you have the information of which nodes the element 294 consists, you can look them up in the Nodes.txt file (same folder).

With this information, you can go into your .blend file and move the cursor to the corresponding position, such that you can see which element is affected. You may manually correct this, or use the MeshGrading tool from https://sourceforge.net/projects/mesh2hrtf-tools/

Hope that helps!

[abidshahriar]

Hi, thanks for the feedback, I really appreciate it because at this moment I am totally feeling lost. So , i have scrolled manually to element #294 in the node.txt file. Its showing (co-ordinates maybe) 0.000098 0.000017 -0.000026. How can i get this point tracked in blender? This question might sound very basic but i am really new to it. And then after tracking the element shoudl i use the grab tool to reduce the triangle size in x,y,z direction where it is most affected? Thank you in advance. @germknoedlspeck

(sorry i closed the issue unfortunately, now its open)

[germknoedlspeck]

No worries, we all started at zero :)

Caution, you scrolled to node 294, but you are looking for 3 nodes that make up the element 294. In Elements.txt, check which 3 nodes (should be integers) make up element 294 and then look up each node in the Nodes.txt file. For each node, move the cursor as you can read here: https://blender.stackexchange.com/questions/13828/precisely-move-the-3d-cursor

Be sure to select the vertex after changing the cursor position so you know the three vertices that make up the element. Keep me posted on your progress!

[abidshahriar]

@germknoedlspeck hi,

i have been trying to fix the errors. I was able to fix the 294 element. Now getting the same error with 123 element. However i am facing trouble to move the 3D cursor to the specific location. I have followed the link you have given. Something very weird that i am finding that is the cursor moves to different location for the given coordinates. And when i move the 3D space it also. I am not sure if it moves to correct location of the nodes. Am I missing something? By the way , i was able to get the nodes value (3 integers the. I located 3integers corresponding coordinates values also). Please let me know if i can contact you outside github.TIA

[abidshahriar]

Hi , @germknoedlspeck

this is a followup if you had any suggestions for me. Thanks

[germknoedlspeck]

I have followed the link you have given. Something very weird that i am finding that is the cursor moves to different location for the given coordinates. And when i move the 3D space it also.

I'm not sure I understand. What exactly is the problem here?

Did you try using the MeshGrading tool from sourceforge?

What I find peculiar is that once you fixed element #294 is that now something is wrong with #123. Can you maybe attach your .blend file so I can have a look at it?

[abidshahriar]

Hi , @germknoedlspeck

Sure. Here is the link of the required file.

https://aiubedu60714-my.sharepoint.com/:f:/g/personal/18-38051-2_student_aiub_edu/EiEk2ch5fQFArVZGegk4QuIBPihHE-LWMy7RLiK5D2pV3Q?e=m1P8yz

(Inside the “Head 3D model Blender file.blend” is the requested file)

I actually went to that file in blender find those 3nodes and identified the element #294 then grab it in blender and maybe i reduce the vertex to negative z direction.

However, appreciate your help to take a look on it.

[germknoedlspeck]

May I ask, which version of Mesh2HRTF and Blender are you using?

[germknoedlspeck]

One problem is that your geometry is not a mesh that is empty inside. When I look at the right ear of 3Dmesh_graded_right from inside the head, there is additional geometry, most probably from the ear canal.

A slightly closer look:

Also be cautious about the units of m or mm when exporting the Mesh2HRTF project. It seems that your mesh is in m, but you exported the Mesh2HRTF projects in mm (so now the information stored in "Nodes.txt" is off by a factor of 1000).

For geometry preprocessing, please have a look at our tutorial: https://github.com/Any2HRTF/Mesh2HRTF/wiki/Basic_3D_Mesh_cleanup_and_merging

[abidshahriar]

Hi, @germknoedlspeck

Good Debug. Ahh, I see! This could probably happened when blocking the ear canal (for Microphone purpose as guided in mesh2hrtf). And yeah about the unit , i was actually missing this and for this reason probably i was getting wrong XYZ position.

One question though, do you suggest me to fix this mesh? Or should i just start from the beginning again. I mean from the merging then blocking ear canal to mesh grading and then finally to the mesh2hrtf? I am bit skeptic if i can fix the current mesh.

Btw , thanks a lot. I will keep posting my updates and get back here.

[germknoedlspeck]

Actually, whatever works for you best. Maybe - since you said you were new at Mesh2HRTF - start all over, just to practice the workflow. At least that is what I would do when I started working with Mesh2HRTF.

❗ ❗ Just an FYI, because I asked for the software versions you are using: If you use the latest Mesh2HRTF release (v0.5.0) or the master branch, you have to work with Blender v2.79 or below (the user interface looks quite different to my screenshots). This is due to a change of the Python version within Blender that started from v2.8 on. ❗ ❗

If you want to keep using a newer Blender version, please clone the repository and switch to the develop branch. This is where we keep v1.0 for the moment.

However, Mesh2HRTF v1.0 will be released soon - also with an accompanying publication, stay tuned! 🎉

Please keep us posted on your progress.

[abidshahriar]

@germknoedlspeck

Thanks and Noted.

I think i used the blender latest version. (Blender 3.5). I will switch to version 2.79 and use the Mesh2HRTF release v0.5.0 (maybe i used that one ). Gonna try again this weekend and will keep it posted here.Thanks for such a supportive community.

[f-brinkmann]

Did not follow the entire thread - but we usually recommend using the latest Mesh2HRTF and Blender version unless there is something specific speaking against that. The new version has more features, is still maintained, and should have a better documentation