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Where is documentation for STL export?
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* April 18, 2016, 09:19:25 PM
I'm having difficulty figuring out the Mesh Parameters settings and there is no Help button for documentation. Default values do not create a smooth enough STL mesh for me. A forum search didn't pull up any relevant results. Where can I find documentation for these settings?

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* April 19, 2016, 01:08:02 AM
#1
Have you tried page 76 of the User Guide? The Mixed/Fringe dropdown isn't talked about there but what it's referring to is a mixture of quads and triangles, the quads are used in flat areas and as the flats approach a curve (fringe area) the facets are changed to triangles. This helps to reduce the number of facets. A proper stl file is all triangles so if you are going to export it for use in another program be careful, it may not like quads. 

Tim Olson has written a Tips and Tricks book that has more info on stl file format. It can be downloaded in pdf format here:

http://www.masterviacad.com/viacadtips/viacadtips.html

Enjoy
Mitch

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* April 19, 2016, 05:14:57 AM
#2
I haven't located a User Guide yet. One didn't unpack with the application download and I've been unable to locate one at turbocad.com - only LTE version (I have PRO version). There is no Mixed/Fringe option in my dialog but I intended to do all triangles anyway. Just having troubles getting sharp edges to not derp-out when the facets count is increased for smoother surfaces.

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* April 19, 2016, 09:23:48 AM
#3
The User Guide is found under the Help menu and the Mixed/Fringe is in the mesh parameters box, uncheck the STL facets box.

Enjoy
Mitch

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* April 19, 2016, 06:47:57 PM
#4
Thanks, the documentation helps (a little) but doesn't answer everything. The one-sentence description for "Aspect Ratio" doesn't give any more explanation than the prompt itself. What is the "maximum allowed aspect ratio"? A ratio is typically two numbers, say, 1:2 - so I'm not seeing how a single value gets applied as an aspect ratio. "Normal Deviation" could be explained a little clearer too, and illustrations showing the effect of each setting, as is provided for "Surface Deviation", would be helpful. No documentation is included in the User Guide for "Adjust Nodes" or "Adaptive Facets" - so what do they do? I intend to leave "STL Facets" enabled since my export is intended for 3D printing so I only want triangles for maximum compatibility.

I would also like to make a recommendation for the Mesh Parameters dialog. Each time it comes up it's reverted back to the default values. It would be more practical having it preserve the last used settings just as nearly all the other forms and tools do. Also, often the dialog's values get corrupted to ridiculous values when moving the form to a different location. It would also be handy having an "Overwrite Exiting Files" added to the Export dialog for bypassing the extra click-through when exporting over an existing file.

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* April 20, 2016, 12:16:58 AM
#5
The User Guide is terse on a lot of subjects and information on how this program works is difficult to find. I do recommend Tim's book, there is a lot of info you can't find anywhere else.

All the questions you have here are addressed in his book. I would rather not quote anything in his book as it has a copyright.

Sorry

Enjoy
Mitch



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* April 20, 2016, 05:01:34 PM
#6
information on how this program works is difficult to find

That is sad and the $400 I spent on this glitchy application should have been used on a different product. Time to go shopping...

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* May 04, 2016, 01:49:14 PM
#7
I will try to get you an answer about on the STL topics mentioned below.

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* May 04, 2016, 09:15:52 PM
#8
I've become very frustrated with TurboCAD's STL export. Here is an example. The model is a closed solid and all the surfaces are smooth (ScreenShot1). After much experimentation (due to lack of documentation) I've come up with settings which yield what appears to be a very smooth mesh (ScreenShot2). However, viewing the exported STL in another application such as Meshmixer, you can see many distortions along the edges (ScreenShot3). The STL file displays the same in all the applications I view it in, so it's obvious to me the fault isn't with the other applications. I have yet to concoct a combination of settings which yields a smooth mesh for 3D printing and no derps along the edges or surfaces. (Hopefully the screen shots upload because they're not displaying when I preview my post.)
« Last Edit: May 05, 2016, 07:48:28 PM by chappa-ai »

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* May 06, 2016, 05:13:17 AM
#9
Also, I don't understand why the primary edges for the facets do not run perpendicular to their associated surface edges. Their orientation is all over the place which I believe to be contributing to the corrupt STL export. I've marked in blue how the facet direction should be oriented for best results, but the faceting algorithm instead butchers up the perimeter of several surfaces on the model making them all garbled. I know the underlying base model to be correct because if I lower the mesh density then STL edges are properly straight. But a lower density is no good for printing.
« Last Edit: May 06, 2016, 05:18:25 AM by chappa-ai »

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* May 06, 2016, 09:34:41 AM
#10
Here is some additional information about STL. We'll investigate your newly reported items, thanks for the details.

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* May 06, 2016, 08:00:47 PM
#11
Thank you. That information belongs in the user manual. I still get deformed edges in the mesh when using an edge length less than 5. It would be so much more user-friendly if the Mesh Parameters (or Mash Parameters, as I've coined it) retained its previous values instead of reverting back to default each time. Most of the other tools retain their settings when reselecting them. If I get a clean enough mesh generated from this glitchy application then I can clean it up in a different application that handles mesh's better.

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* May 10, 2016, 12:51:38 PM
#12
>>I don't understand why the primary edges for the facets do not run perpendicular to their associated surface edges.

Facet vertices are created along the underlying 2D parameter space grid for a face.   From the image you attached, it looks like the face being faceted is an analytic face. An analytic planar face is defined by a point and normal plus boundary curves. Boundary curves have no effect on the parameterization and hence faceting.  For some NURB faces such as a skin surface, the original edges do influence parameterization. Trim curves (cut outs,holes,etc) never influence parameterization and are typically defined by parameterization. 

This is correct behavior for all ACIS based apps. I also believe true for ParaSolids and any kernel supporting analytic surfaces.   

>>Their orientation is all over the place which I believe to be contributing to the corrupt STL export.

Can you provide and example of a corrupt TurboCAD STL file? 

>>retained its previous values instead of reverting back to default each time

The Mesh Dialog shows you the settings of the selected object which is consistent with most dialogs.  I believe you want to see the settings for the object you are seeing on the screen.  If you select a solid, the dialog will show you the mesh settings related to the display list (SuperFine, Fine, Medium, etc) which is what you see on the screen.  The display list only uses Normal Deviation where SuperFine = 5 degrees, and Fine = 12 degrees.

>>But a lower density is no good for printing.

My understanding is that you want a mesh model that represents the analytic/NURB model to a given tolerance.  Normal Deviation and Surface Deviation are two excellent parameters.  Normal Deviation is model size independent and will capture shape based on curvature.  Surface Deviation will get those other instances where small changes over long spans that normal deviation might miss.

From the image you posted it looks like you have turned off Normal & Surface deviation in preference to only Edge Length. With this setting you might miss detail below the Edge Length plus add many facets to places not needed.  For example, your planar faces may have more facets than needed to define the shape.

One other thing to note is that the 3D printer does not drive the print head from facets. It generates a 2D slice through the facets.  So the only thing the facets are used for are creating a closed 2D region.

If you have a corrupt STL file I'd really like to see that and send off the to guys at Dassault.   If you can send to IMSI tech support that would most appreciative!  An easy check is to read the STL file back into TurboCAD. If the issue is not present, then it may be an issue with the other app reading the STL.

Hopes this helps clarify some of the meshing better!

Tim Olson
TurboCAD Mac Development









« Last Edit: May 10, 2016, 04:21:28 PM by Tim Olson »

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* May 10, 2016, 06:33:50 PM
#13
Thanks much for the reply! Yes, indeed it does seem like I made a boo-boo in the mesh settings by setting the deviation values to zero rather than using a very small value (0.01?). I will try again. I've been experimenting through trial and error (mostly error) at trying to determine the right combination of these settings to generate a high-quality mesh for printing.

What I mean by the dialog not retaining previous values is, my project contains only one closed solid (at least on the layer being exported). So when I initially export to STL I do expect the dialog to start out with the default values. But, after exporting, if I go and export the same object again then the dialog opens up with default values instead of the last used settings. If I rotate an object 18 degrees, the next time I select the rotate tool it will still show 18 degrees until I change the angle. But when I export to STL the Mesh Parameters dialog does not show the last values used - it always shows the default values. This means I need to write them down in order to remember the settings for tuning subsequent exports. Even worse, moving the dialog to a different location causes garbage values to appear in the entry fields.

When I say the STL file is corrupt, I mean that edges which are flat on the model are garbled in the STL file and surfaces which are smooth on the model are distorted in the STL file (see ScreenShot3 from my previous post). I would be happy to send example TCP and STL files to somebody to look at (and maybe even provide me with proper settings for a decent STL file!) but I'd need to know where to send it to (and know that they're expecting the files). I've learned in the past that such files cannot be uploaded here on the forum.
« Last Edit: May 10, 2016, 07:35:27 PM by chappa-ai »

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* May 10, 2016, 07:28:44 PM
#14
Nope. I tried a value of 1 for all the settings, and although I got what looks to be a smooth mesh (ScreenShot4), the STL file still has garbled edges when viewed in MeshMixer (ScreenShot5), won't open at all in Netfabb (invalid STL error), and also fails to open in Dremel 3D. So, despite MeshMixer being able to open the file, it would seem the generated STL is junk and it should not be this difficult just to export a dang 3D printer file from TurboCAD!

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