Full Version: exporting 2d

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Hi adx, circles and ellipses will end up as what is known as a "rational" spline in the DXF file, where it has an additional weight value assigned for each control point. It sounds like your target application may not fully support this type of spline curve.

But I'd like to check to see if there is any bug in writing the DXF file, could you please send me one of the files that is not working right? You can e-mail it to me at moi@moi3d.com .

For AI export - AI doesn't actually support exact arcs or ellipses, or rational splines, it only supports bezier curves. So when you do an AI export MoI has to approximate some kinds of curves by a type of refitting process. Right now this is done to a tolerance of 0.05 units, so if you have curves that are pretty small, they will get approximated rather roughly.

If you could send me a sample .3dm and .ai file for that problem as well, I could see if I can fix that up to work better.

- Michael

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Hi, excellent support there.

I found that the DXFs view correctly in the SolidWorks model viewer and Alibre, so it's Qcad that is working incorrectly, screenshot attached along with shot of the original (1600*1200 sorry). SheetCAM, most G code output, and things like my PCB design package (Protel, my day job) can only deal directly with lines and circular arcs, hence my interest in that. I had been using Qcad to import features that need to be converted to polylines (like ellipses), maybe not such a good idea.

I couldn't replicate the .ai issue clearly in Xara this time. It was just a file I drew very similar to the attachment shown, and deleted after playing. Your description of the approximation sounds rational (no pun intended), the thing I drew was very small.

If I come across any clear examples I'll send them. In the mean time my vote is for 2D export of circular arcs and straight line features if that's possible, so they can be directly imported into 2.5D CAM or non-mechancial CAD systems.

Thanks - Antony.

Attachments:
plate-test2.3dm.moi.png
plate-test2.dxf.qcad.png

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Hi Anthony, based on your screenshot, it does look like the weights are not being read in QCad.

However, looking into it there appears to be an additional flag that I can set to mark the spline as having weights. It appears that most programs will read the weights if they are present regardless of whether the flag is in place, but maybe QCad will only read them if the flag is set.

Can you please try the attached test_qcad_circle.dxf file and see if this one will read into QCad properly? This one has that flag set on it.


> the thing I drew was very small.

Yeah, it was most likely related to the small size. I'll look into tuning this up, I should be able to look at the size of the curve and if it is small I will use a tighter tolerance for the refitting process.

- Michael

Attachments:
test_qcad_circle.zip

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Hi Anthony, I also updated the converter program ( http://moi3d.com/download/3dmCurves2DXF.zip ) to write this additional flag as well, so if that circle works then grab this new version.

> In the mean time my vote is for 2D export of circular arcs and straight line
> features if that's possible, so they can be directly imported into 2.5D CAM
> or non-mechancial CAD systems.

Yes, when I get to this point for version 2 I want to have several options for DWG/DXF export, whether to export as splines, use arc and line entities, or break things into polylines.

- Michael

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Thanks again, I've been slow to check this forum, busy.

I tried the circles dxf with much the the same result as before. The circle is 'square' as seen in the 3rd attachment, also if I try to make it round you can also see there is a sharp node (maybe start and finish) in attachment 1. An import straight into SheetCam converts it to polylines, very similar to QCad, otherwise I'd say the problem is limited completely to QCad.

I wouldn't worry about it too much, if extraction of arc and line entities is on the drawing board then that's good enough for me!

BTW I did something useful in 3D lastnight and it was all done in 15 mins. Apart from a little playing on SolidWorks and over the years and more recently with Alibre, I'm no 3D designer. Very cool. I might make a gallery post.

- Antony.

Attachments:
test_qcad_circle-modified.png
test_qcad_circle-sheetcam.png
test_qcad_circle.png

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>>Hi Paul, I cooked up a converter for you, you can download it from here:
>>http://moi3d.com/download/3dmCurves2DXF.zip
>>
>>Unzip this to some folder, then run the 3dmCurves2DXF.exe program.
>>
>>It will ask you for the name of an input .3dm file, and then the name of an output .dxf file.
>>
>>It will read through the input .3dm file and convert any curve objects it finds to Spline entities in the DXF file.
>>
>>Please let me know if this works to transfer your curve data over.
>>
>>- Michael

I know this thread is almost 3 years old, but when something works you have to give credit. This works perfectly! I drew an object using simple lines in the "TOP" view, and then converted the 3DM to a DXF file. That file will now be used to laser cut gaskets in .010" copper.

Brilliant!

Thanks,

Chris

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