How to do Quad mesh?

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maxcwy2017
Posts: 21
Joined: Mon Nov 02, 2020 2:30 pm

How to do Quad mesh?

Postby maxcwy2017 » Mon Nov 02, 2020 2:32 pm

I wanted to do Quad mesh instead of Triangle mesh but it seems that I could not find the option for the feature? So is there any way to do a Quad mesh?
chrisb
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Joined: Tue Mar 17, 2015 9:14 am

Re: How to do Quad mesh?

Postby chrisb » Mon Nov 02, 2020 3:48 pm

Hi and welcome to the forum!

No, there is no such option. Triangles are rather easy to handle, while other geometries may cause less lines, but are more difficult to handle. As FreeCAD is not really a Mesher, it is not optimized for such things.
You need at least FreeCAD 0.19.23300 to edit my current sketches.
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Syres
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Joined: Thu Aug 09, 2018 11:14 am

Re: How to do Quad mesh?

Postby Syres » Mon Nov 02, 2020 9:23 pm

chrisb wrote:
Mon Nov 02, 2020 3:48 pm
No, there is no such option.
You're partly correct, there's no 3D Quad mesher available in FreeCAD by default but there is a 2D surface quad mesher:

QuadMesh.jpg
QuadMesh.jpg (163.03 KiB) Viewed 330 times

Using FEM GMSH with the setting as ellipse'd in red. This was gleaned from https://forum.freecadweb.org/viewtopic.php?t=20351

OS: Windows 7 SP 1 (6.1)
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Word size of FreeCAD: 64-bit
Version: 0.19.22882 (Git)
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Edit: Slapped wrist for not putting FC Info in post.
maxcwy2017
Posts: 21
Joined: Mon Nov 02, 2020 2:30 pm

Re: How to do Quad mesh?

Postby maxcwy2017 » Tue Nov 03, 2020 6:23 am

I see because I need to a simulation with my model. 2D meshing should not be able to get the job done right? And in the video of the instructions I was given with for AVL FIRE, the person use quad meshing instead of triangle, so I was wondering, if it will be wrong if I didn't follow what was show in the video.
mrdic
Posts: 86
Joined: Wed May 10, 2017 4:25 am

Re: How to do Quad mesh?

Postby mrdic » Tue Nov 03, 2020 6:56 am

Not FreeCAD, but there's an open source program called Instant Meshes, https://github.com/wjakob/instant-meshes. Converts tris and n-gons to quads, not a lot of documentation, lots of trial and error, but pretty good.
maxcwy2017
Posts: 21
Joined: Mon Nov 02, 2020 2:30 pm

Re: How to do Quad mesh?

Postby maxcwy2017 » Tue Nov 03, 2020 9:12 am

mrdic wrote:
Tue Nov 03, 2020 6:56 am
Not FreeCAD, but there's an open source program called Instant Meshes, https://github.com/wjakob/instant-meshes. Converts tris and n-gons to quads, not a lot of documentation, lots of trial and error, but pretty good.
It's 3D meshing right? Because I need to transfer it to AVL FIRE and making a simulation by using that model. But then the video I got for the steps to prepare the model for a simulation is completely Quadmesh without converting triangles. So it might make the steps a bit different.
mrdic
Posts: 86
Joined: Wed May 10, 2017 4:25 am

Re: How to do Quad mesh?

Postby mrdic » Tue Nov 03, 2020 11:34 am

keithsloan52
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Joined: Mon Feb 27, 2012 5:31 pm

Re: How to do Quad mesh?

Postby keithsloan52 » Tue Nov 03, 2020 12:06 pm

My GDML workbench can create Quad and Triangle GDML Tessellated meshes. (Some shapes have a problem with Quad meshes).
Trouble is if you then use the facility to convert back to a FreeCAD mesh it makes the result with only triangles.

I use the Gmsh python library which is different from the Mesh workbench ( which is written in C++ I believe) but I don't believe it would be too difficult to update the FreeCAD mesh workbench to add support for quads using the Gmsh option.
maxcwy2017
Posts: 21
Joined: Mon Nov 02, 2020 2:30 pm

Re: How to do Quad mesh?

Postby maxcwy2017 » Tue Nov 03, 2020 12:45 pm

After I completed meshing my model, I exported it into OBJ file and after that I converted it into STL file. When I opened the file with AVL FIRE, the Quad meshes are formed by 2 triangle mesh. Is my settings on instant mesh incorrect or is it the way that the quads are formed by merging 2 triangle mesh? Because I was hoping it to be only Quad mesh like the photo I attached below.
Attachments
Quadmesh4.PNG
Quadmesh4.PNG (309.73 KiB) Viewed 196 times
maxcwy2017
Posts: 21
Joined: Mon Nov 02, 2020 2:30 pm

Re: How to do Quad mesh?

Postby maxcwy2017 » Tue Nov 03, 2020 12:46 pm

keithsloan52 wrote:
Tue Nov 03, 2020 12:06 pm
My GDML workbench can create Quad and Triangle GDML Tessellated meshes. (Some shapes have a problem with Quad meshes).
Trouble is if you then use the facility to convert back to a FreeCAD mesh it makes the result with only triangles.

I use the Gmsh python library which is different from the Mesh workbench ( which is written in C++ I believe) but I don't believe it would be too difficult to update the FreeCAD mesh workbench to add support for quads using the Gmsh option.
Do you have the steps to do it? Because I am new to this so I am not quite familiar with the way it should be done.