quickest way to align a guitar shape

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acp693
Posts: 127
Joined: Wed Dec 15, 2021 7:41 pm

quickest way to align a guitar shape

Post by acp693 »

I have a spline in the shape of a guitar body that I need to align exactly to the x axis in freecad. What I've been doing is to estimate the widest points of the guitar and draw construction lines at those places, then using the centre of those lines to draw another line which should be the centre line of the shape, Using trimex to extend that line and then selecting everything and use the move and rotate controls in Draft Workbench to align.

What I've found though is that isn't exact. Probably because the initial lines at the widest points of the guitar are a guess. Sometimes I go through two or three iterations of this process until I'm happy that it's pretty precisely aligned.

Does anyone have a better, quicker, more precise method for aligning shapes like these? Many thanks!

Code: Select all

OS: Windows 10 Version 2009
Word size of FreeCAD: 64-bit
Version: 0.21.0.32532 (Git)
Build type: Release
Branch: master
Hash: 20e44eba50e1365b9e7bb9c5c244afe96a627a28
Python 3.10.10, Qt 5.15.8, Coin 4.0.0, Vtk 9.1.0, OCC 7.6.3
Locale: German/Germany (de_DE)
Installed mods: 
  * CurvedShapes 1.0.4
  * Curves 0.5.3
  * ExtremeProLight 1.4.3
  * FeedsAndSpeeds 0.5.0
  * Marz 0.0.26-alpha
  * Silk 1.0.0
Attachments
GuitarForm.FCStd
(13.6 KiB) Downloaded 8 times
chrisb
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Re: quickest way to align a guitar shape

Post by chrisb »

I would go for a B-spline in Sketcher. In 0.21 you have improved possibilities to use constraints on the B-spline.
You should also consider to model only half of the guitar and mirror the other half.
A Sketcher Lecture with in-depth information is available in English, auf Deutsch, en français, en español.
acp693
Posts: 127
Joined: Wed Dec 15, 2021 7:41 pm

Re: quickest way to align a guitar shape

Post by acp693 »

Thanks @chrisb. It's not possible to model only half as the B-spline as it is generated from an imported drawing. The drawing are scans and are never aligned perfectly.

Could you elaborate about the B-Spline constraints and how I would use them to align the guitar shape?

Just trying B-Spline in Sketcher and it doesn't seem possible to trace a drawing very easily. In B-Spline in Draft, the b-spline goes exactly through the points placed, making it easy to trace a drawing.
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hammax
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Location: Ammersee DE

Re: quickest way to align a guitar shape

Post by hammax »

... please have a look at the difference in the Curvature_Combs.
BSpline is not Bspline in any case:

GuitarForm_2.PNG
GuitarForm_2.PNG (17.81 KiB) Viewed 356 times
Attachments
GuitarForm_2.FCStd
FC.20.1
(23.18 KiB) Downloaded 4 times
chrisb
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Re: quickest way to align a guitar shape

Post by chrisb »

acp693 wrote: Sun Apr 02, 2023 9:52 am Just trying B-Spline in Sketcher and it doesn't seem possible to trace a drawing very easily. In B-Spline in Draft, the b-spline goes exactly through the points placed, making it easy to trace a drawing.
Tracing is easier in Draft. Then convert it in Draft to a sketch, because editing is easier there.
acp693 wrote: Sun Apr 02, 2023 9:52 am It's not possible to model only half as the B-spline as it is generated from an imported drawing
The fact that you get more data doesn't mean that you have to use it.
A Sketcher Lecture with in-depth information is available in English, auf Deutsch, en français, en español.
acp693
Posts: 127
Joined: Wed Dec 15, 2021 7:41 pm

Re: quickest way to align a guitar shape

Post by acp693 »

@hammax Thanks for looking at it. I'm not sure what you mean with Bspline is not Bspline? And what do the Curvature Combs tell me?

I would just like to align my Bspline so that the X axis runs precisely through the middle of the widest points of the guitar. I don't need to redraw it, simply align the existing drawing.

Thanks for your contribution
acp693
Posts: 127
Joined: Wed Dec 15, 2021 7:41 pm

Re: quickest way to align a guitar shape

Post by acp693 »

chrisb wrote: Sun Apr 02, 2023 10:17 am
acp693 wrote: Sun Apr 02, 2023 9:52 am Just trying B-Spline in Sketcher and it doesn't seem possible to trace a drawing very easily. In B-Spline in Draft, the b-spline goes exactly through the points placed, making it easy to trace a drawing.
Tracing is easier in Draft. Then convert it in Draft to a sketch, because editing is easier there.
acp693 wrote: Sun Apr 02, 2023 9:52 am It's not possible to model only half as the B-spline as it is generated from an imported drawing
The fact that you get more data doesn't mean that you have to use it.
Hi Chris, thank you for your help. I don't want to edit the bspline, simply move it until the middle of the widest points of the guitar are aligned with the x axis. The drawing is slightly asymmetrical - the two halfs aren't entirely identical. I want to retain that asymmetry.
chrisb
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Re: quickest way to align a guitar shape

Post by chrisb »

acp693 wrote: Sun Apr 02, 2023 10:23 am I would just like to align my Bspline so that the X axis runs precisely through the middle of the widest points
In Sketcher you can now constrain a vertical line to a B-spline, which gives you the rightmost point.
A Sketcher Lecture with in-depth information is available in English, auf Deutsch, en français, en español.
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