STL File - Mesh Surface Problems
 

Hi Everyone!

My first time here, and I like what I see! Great stuff!

I'm having major problems using Gambit. I've been trying to import an STL file into Gambit, which can read and open the file, but the faces are labelled as f_face. These are not real faces, and there are no vertices or lines. The STL file is a surface mesh file. I need to manipulate the file such that I can obtain a "real" surface or solid. Stitching the faces didn't help, 'cos the faces are not "real". I'm at a loss.

I got the STL files from CT scans. But Gambit can't seem to read them as real surfaces or as a solid. Does anyone know anything about this? Is there a converter I can use? Please help, as I'm completely stuck and have not been progressing for ages, and I'm getting a bit depressed. Thanks people!

Harmeet.

Re: STL File - Mesh Surface Problems
 

Well, should you be using ICEM or Pro*am, it would be easy to give you an answer. But geometry reconstruction using STL data in Gambit - I can't imagine how that could be done.

You see, compared to what you need, Gambit uses a completely different strategy for meshing - first you must define geometry (kind of block structure of your mesh) and you then create the mesh for the individual pieces of the geometry. I can hardly imagine how you could create some logical volumes from the almost random triangulation which is typical for STL format.

Sorry for the bad news and good luck,

George

Re: STL File - Mesh Surface Problems
 

Hi George,

Thanks for the reply. I'm considering switching to ICEM to get this done. I've never used it before. My problem involves importing an STL file. I suppose that the software will recognise the surfaces right? Basically I need to import the STL image, nd then create a geometry around it and then do the flow analysis.

I've never used ICEM before or CFX. Can you please advise as to how I should proceed? Where would be a good place to start? Any recommended sequence of what I should do? Thanks a million George!

***Would it be possible to contact you via E-mail please? My E-mail add is g0301488@nus.edu.sg .

Re: STL File - Mesh Surface Problems
 

Hi Harmeet,

I didn't say CFX, I talked just pre-processor stuff. And I'm sorry, I'm currently only Gambit user, though I know pro*am (advanced preprocessor of Star-CD) from previous experience and ICEM as well. They use a different strategy, compared to Gambit, which makes it well suited for the kind of problem you have.

I hope this helps,

George

Hi,

Obviously this is a old thread but I came across it searching for something else,
but I use gambit to mesh STL geometry and it works fine.

So for anyone else who may come across this thread with a similar problem:

I import the STL (or STLs) into gambit,
then delete the surface mesh,
I can then split these surfaces anyway I like (using split faces(virtual)),
a virtual volume can then be created from these faces using stitch faces.

This volume (or volumes) can then be meshes any way you like (well obviously it typically takes a bit of manual splitting before mapped hex is possible).

Then you can define your boundaries and export the mesh!


Any problems, just ask.


Philip


BTW: "GEOMETRY.FACE.VIRTUAL_FACE_FACE_SPLIT" in "Edit -> Defaults" should be set to "1" to perform the face/surface splitting operations.

Hi Philip
I just read your commnet about import of STL surface mesh in Gambit. I am at this moment facing similar problem. I would like to simulate flow field inside a porous 3D object. I received geometry frm nanotomography in STL format. I was succesful in importing STL surfaces and costruction of virtual volume ut of them. Now I am stack with subtraction of this virtual volume from a cube around it (to get only volume of voids). Gambit is complaining about working with non-real geometry. Do you have any idea how can I make this subtraction?

Many thanks

MiroS

Hi MiroS,

OK I think I understand your problem. I think Gambit does not like performing boolean operations with un-real geometry so you will not be able to subtract your volume from a cube volume, but I think it should be possible to create the voids volume in Gambit some other way.

Hmmnn I am not sure but if you have the the faces of the void and the faces of the surrounding cube, it should be possible to create a volume from these faces (stitching them together). Also you would probably have to split the cube faces with the STL face before stitching so as the inner STL and outer cube faces stitch together.

Let me know how you get on,
If you would like you could upload the STL here or email to me and I could have a look at it when I have some free time. My email is philipcardiff AT gmail DOT com.

Philip

Many thanks Philip
I am now trying procedure as you described. Let us see how far I can go. Unfortunately STL files are quite big.

MiroS

booleans
 

You can do a boolean with the cad package Rhinoceros ( Rhino to most ). Import the stl, convert it to a Rhino mesh ( MeshtoNurbs) , construct the outer block and presto...Save that subtracted block as a new stl.