Drawings with splines don't save and open well

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sguttag
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Joined: Sun Mar 10, 2019 8:17 pm

Drawings with splines don't save and open well

Post by sguttag » Wed Oct 21, 2020 8:55 pm

I will often get a drawing from a manufacturer of their product so I can place it into a drawing. More often than not, these drawings will consist of a lot of splines to make their shapes.

Now, when I open them, they look fine. I can copy and paste them without issue (within the same drawing or copy them into a new drawing). Everything looks great...until I open that drawing again. At that point, a large portion of the splines are gone so the image looks mostly gone too. This is platform independent (I've tried it on Mac and PC) and on the current version of QCAD too.

Now, by experimenting...if I "Explode" the splines and configure the Explode Splines to Polylines, then I get a version that can be saved. Is that normal?

This is what the control panel looks like when I open the manufacturer's file or when I copy about:
EpradControl.JPG
EpradControl.JPG (139.6 KiB) Viewed 302 times
Here is what it looks like after saving and reopening:
EpradAfterSave.JPG
EpradAfterSave.JPG (96.89 KiB) Viewed 302 times
Here is the original file:
LCS Dimmer.dwg
(502.42 KiB) Downloaded 23 times
And here is what happens to it after it is saved (dxf or dwg, it doesn't matter):
EpradControl.dxf
(1.17 MiB) Downloaded 17 times
Also, are the default settings for the spline to polyline good ones to start with? What is the best way to trim the file size without losing (too much) detail?

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Husky
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Re: Drawings with splines don't save and open well

Post by Husky » Thu Oct 22, 2020 1:56 am

@sguttag
I don't have a solution (maybe a workaround) but I can reproduce the issue.

@Andrew
The splines which are causing the issue are built with Degree 3 splines. It is difficult to select them with the mouse ...
However - if you change the degree to 2 the drawing can be properly saved and will load again without missing entities. After that you can change it back to degree 3 and it is still working ...
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CVH
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Re: Drawings with splines don't save and open well

Post by CVH » Thu Oct 22, 2020 9:30 am

QCADpro 3.25.2.1 / win7pro 32 bit

No problem selecting.
No problem saving, nor dwg, nor dxf.
Nor R27, nor R32, nor R14. (Original = dwgR14)
No problem select, copy, paste on new drawing & save dxfR27, revert.
No problem after reboot, reload.

Qubic splines are pretty common.

Regards,
CVH
QCADpro 3.25.2.1 / win7pro 32 bit / 4GB / 1e generation i7 2.6Ghz / HDD GeForce GT 520

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andrew
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Re: Drawings with splines don't save and open well

Post by andrew » Thu Oct 22, 2020 9:47 am

Unfortunately, this is an issue with the OpenDesign libraries (19.x, 20.x). I've reported the issue and hopefully they will provide a fix or a workaround.

As CVH has pointed out, the Windows 32bit package might be a workaround for you at this point as it still uses the OpenDesign libraries version 4.

Note: These are splines that cannot be produced with QCAD itself (with clamped knot values or "corners" in the middle of the spline).

CVH
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Location: Belgium; Antwerp

Re: Drawings with splines don't save and open well

Post by CVH » Thu Oct 22, 2020 10:25 am

Not to prove you wrong because it is indeed a different type of splines.

But I think I got this from the QCAD forum.
Spline from control points, qubic, closed:
- click 3 times every hard corner, start with 1 time for the first and ending with 2 times the first again.
LCS Dimmer snip.dxf
(152.3 KiB) Downloaded 15 times
Regards,
CVH
QCADpro 3.25.2.1 / win7pro 32 bit / 4GB / 1e generation i7 2.6Ghz / HDD GeForce GT 520

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andrew
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Re: Drawings with splines don't save and open well

Post by andrew » Thu Oct 22, 2020 10:58 am

You can have multiple identical control points in the middle, but you can't clamp them in QCAD (i.e. same value for the knot vector for multiple points that are not end points).

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andrew
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Re: Drawings with splines don't save and open well

Post by andrew » Fri Oct 23, 2020 1:44 pm

I've reported this to OpenDesign and they confirmed the bug. For now, we'll roll back to OpenDesign 4.x where possible.

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