STL Triangulation

[soheyl81]

I'm trying to export a geometry (let's say a simple cylinder) created in NX into the STL format, and I want to get a fine triangulation pattern with reasonable aspect ratios, similar to what you create in a mesh for FEA for example. However, I am getting a series of triangles with really high aspect ratios. Using tighter tolerances in the export options results in more point around the circular edges, but no refinement along the cylinder axis. Please see the attached picture. Is there anyway to export STL files with a nice triangulation pattern in NX, or in any other software that you may know of?

 

[markrief]

I am not sure what your downstream requirement is, but you might try File --> Export --> Polygon File. This allows you to enter the maximum triangle edge length when you export. Perhaps you can convert this to stl. If you don's see the option, ot probably requires a special CAM license.

I am curious, is there a technical reason why you need to limit this?



Mark Rief
Product Manager
Siemens PLM

 

[JohnRBaker]

For what .stl files were designed for, that is passing a 3D model to a rapid-prototyping machine, this type of tessellated result is exactly what would be expected. After all, this is NOT an application to create a mesh for something like an FEA simulation, where aspect ratio can be an issue.

But to answer your question, NO, there's NO way to control the aspect ratio of the tessellations created by the...

NX -> File -> Export -> STL...

...function. If you need to control the aspect ratio in this way, you will need to use an actual mesh generation routine, such as found in the NX FEM modules.

John R. Baker, P.E.
Product 'Evangelist'
Product Engineering Software
Siemens PLM Software Inc.
Industry Sector
Cypress, CA
Siemens PLM:
UG/NX Museum:

To an Engineer, the glass is twice as big as it needs to be.

 

[soheyl81]

Yes, my application is not typical. I'm going to import this file into an open-source DEM code that uses this triangulation of the imported STL file in the post-processing of the results. Thus, refined better shaped triangles will create more meaningful contours.

Technically, it shouldn't be impossible, since the STL file is just a list of node coordinates grouped together for each triangle. I should be able to write a small code to convert a 2D surface mesh data (or polygon file as suggested by Mark) into this format. But before doing it, I want to make sure that there isn't an easier way, and that I'm not reinventing the wheel.

 

[JohnRBaker]

May I suggest that you're looking for something which does NOT exist.

Now I don't mean that there's no way to get a so-called finer mesh. What I mean is that it's not going to gain you any benefit.

Take for example your simple cylinder model; even if you could have gotten the model tessellated in the way you think it should be, this would in NO way have enhanced the 'quality' of the faces nor the faithfulness of the overall shape of the model. The result would only be a larger set of data. In fact, there's the potential that a model like your cylinder, if it were represented by a very fine tessellation, could actually result in a poorer quality output. More data does NOT automatically make something more precise nor assure that it will more accurately represents the original shape of the model, it just means that the final application will have more data to digest thus providing more chances for mismatches and misalignments.

John R. Baker, P.E.
Product 'Evangelist'
Product Engineering Software
Siemens PLM Software Inc.
Industry Sector
Cypress, CA
Siemens PLM:
UG/NX Museum:

To an Engineer, the glass is twice as big as it needs to be.