Personal tools
You are here: Home Use Wrong mesh made by Body Fitting Algo

Wrong mesh made by Body Fitting Algo

Up to Use

Wrong mesh made by Body Fitting Algo

Posted by Hao BAI at July 20. 2012

Hi,

I try to mesh a hexahedral solid by using the method Body Fitting. So that I can obtain a mesh of Cartesien (la Boite a Sucre). Everything is OK and the mesh computation is succeeded. But the result is so strange (shown in the attachment). I don't know why the edges are like sawtooth but not just a line!

I attach the geometrical view of my solid in the second reply, and here's the link to download all my shapes for someone who may want to do some experiments:

The objets that should be meshed are named "Solid_1, _3, _4" and "Solid_5". You can mesh anyone as you like. The result is the same for all of them. There's always a sawtooth in all the edges.

Any help will be appreciated!

Attachments

Re: Wrong mesh made by Body Fitting Algo

Posted by Hao BAI at July 20. 2012

Here's the view of the solid in GEOM module. (a hexahedral solid)

Regards

Attachments

Re: Wrong mesh made by Body Fitting Algo

Posted by DAVID Gilles at July 20. 2012

Hello,

You have to increase the threshold value. Any element size (area, edge length ? I don't know) below this value will be removed.

Regards,

Gilles

Re: Wrong mesh made by Body Fitting Algo

Posted by Hao BAI at July 20. 2012

Previously DAVID Gilles wrote:

Hello,

You have to increase the threshold value. Any element size (area, edge length ? I don't know) below this value will be removed.

Regards,

Gilles

Hello,

This mesh is made by using the maximum of the threshold (=1e10) as in the attachment. I also tried to reduce the size of the element to 25*25*50. But the problem is always be there.

Regards

Hao
Attachments

Re: Wrong mesh made by Body Fitting Algo

Posted by Saint Michael at July 20. 2012

Hi Hao,
try to decrease Z spacing.

St.Michael

Re: Wrong mesh made by Body Fitting Algo

Posted by Hao BAI at July 23. 2012

Previously Saint Michael wrote:

Hi Hao,
try to decrease Z spacing.

St.Michael

Hi Michael,

I've tried that way, and like in the attachment, there's always some so strange "holes". But the calcul is succeeded !

Hao
Attachments

Re: Wrong mesh made by Body Fitting Algo

Posted by Hao BAI at July 23. 2012

P.S. Something more about that picture attached, it was made by a size of 200*200*1.

Re: Wrong mesh made by Body Fitting Algo

Posted by Saint Michael at July 23. 2012

Hi Hao

Apparently your shapes are not suitable for Body Fitting algo. I think it's possible to make a hexahedral mesh using quadrangles already present in your shape. I can create a script doing this if it's OK for you.

St.Michael

Re: Wrong mesh made by Body Fitting Algo

Posted by Hao BAI at July 23. 2012

Hi,

I've already tried to mesh my solid by Hexahedralization algorithm:

3D : Hexahedron (i,j,k)

1D: Wire discretisation

Hypothese for 1D: Nb. Segments = 2 OR Max Size = 78 OR Local Length = 200

All of this lead me to an error during the calculation as in this picture :

(â†‘sorry, I can't attach a file more than 100k in this forum.)

I don't know if this is the method that you want to try ? If so, well, at least the calculating is failed in my computer. If not, please show me your idea.

Hao

Re: Wrong mesh made by Body Fitting Algo

Posted by Saint Michael at July 23. 2012

Your shape is neither suitable for Hexahedron(i,j,k), which requires that a shape to be a 6-sided solid (box). Hexa(i,j,k) would work if you created boxes of your quadrangles when constructing your shape.

My idea is make a 2D mesh on your shape and then to find corresponding top and bottom quadrangles to make hexahedrons on them in a script.

St.Michael

Re: Wrong mesh made by Body Fitting Algo

Posted by Hao BAI at July 23. 2012

Previously Saint Michael wrote:

Your shape is neither suitable for Hexahedron(i,j,k), which requires that a shape to be a 6-sided solid (box). Hexa(i,j,k) would work if you created boxes of your quadrangles when constructing your shape.

My idea is make a 2D mesh on your shape and then to find corresponding top and bottom quadrangles to make hexahedrons on them in a script.

St.Michael

I tried my best to do as you say, but I didn't succeed... Could you please write a script for me to mesh it as you said ? -- If this does not disturb you too much -- You can choose just 1 solid to mesh as you wish (e.g. Solid_4). I can learn your script and try to apply it to all the other solids by myself.

Thanks Michael !

Re: Wrong mesh made by Body Fitting Algo

Posted by Saint Michael at July 23. 2012

Here is the script. On Solid_1.brep it create all but 2 prisms.

St. Michael

Attachments