Importing Splines

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Jam35
Junior Member
Posts: 12
Joined: Thu Jul 05, 2018 11:49 am

Importing Splines

Post by Jam35 » Wed Sep 15, 2021 12:30 pm

I have a customer that sends me DXFs to produce shapes on flat glass CNC.
Sometimes they will send a curved shape e.g. in this case, an oval / ellipse.
The shape will import as a spline but what I see in QCAD is not the expected result.
At least, and I'm not sure if it is a QCAD problem at all, what I am seeing is not what the customer thinks he has sent...

In the attached file, the shape is not a true ellipse but what looks like a bloated version of one.

Can anybody explain what is happening here?

I believe they are using Rhino CAD to produce the file.


Thanks.

Win 10 Pro
QCAD V3.26.4
Attachments
tapel top Curve - not the square n.dxf
(160.03 KiB) Downloaded 292 times

CVH
Premier Member
Posts: 3416
Joined: Wed Sep 27, 2017 4:17 pm

Re: Importing Splines

Post by CVH » Wed Sep 15, 2021 2:02 pm

Hi,

Should this be an ellipse of 805 by 560?
The representation by a second order spline is odd.

It could be that this is a spline type that is not supported ...
e.g. I can't reproduce the shape by the 9 control points whatever I use as spline degree.

Regards,
CVH

Jam35
Junior Member
Posts: 12
Joined: Thu Jul 05, 2018 11:49 am

Re: Importing Splines

Post by Jam35 » Wed Sep 15, 2021 2:40 pm

Yes, they tell me it is supposed to be an ellipse.

No, I played with those settings also to no avail.

No worries, I will just be more careful to check when they send this type of drawing.
Unfortunately a few times we have produced incorrect glass because of this.
Maybe they can explode the splines before sending. :roll:

Many thanks.

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andrew
Site Admin
Posts: 9037
Joined: Fri Mar 30, 2007 6:07 am

Re: Importing Splines

Post by andrew » Wed Sep 15, 2021 2:45 pm

The spline uses control points with different weights. I can confirm that this is not currently supported by QCAD.

Jam35
Junior Member
Posts: 12
Joined: Thu Jul 05, 2018 11:49 am

Re: Importing Splines

Post by Jam35 » Wed Sep 15, 2021 2:54 pm

Thanks.

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