Constrain a point in a b-spline.

[codeborg00]

Hello forum members,

OS: Ubuntu 21.04 (ubuntu:GNOME/ubuntu)
Word size of OS: 64-bit
Word size of FreeCAD: 64-bit
Version: 0.19.
Build type: Release
Python version: 3.9.2
Qt version: 5.15.2
Coin version: 4.0.0
OCC version: 7.5.1
Locale: English/United States (en_US)


I am a relatively new FreeCAD user and have been trying to follow a tutorial which details how to model an a380 airliner.
Link to tutorial: https://www.youtube.com/watch?v=dRCKmc0ZxBk

This tutorial is for solidworks, however I figured it should all be possible to do in FreeCAD. Unfortunately, I have come across an issue at 23:14(tutorial timestamp). I am unable to constrain the B-spline as shown in the tutorial. I have attached the file which I am working on. I was wondering if anybody has a solution to my problem.

Thank you in advance

[chrisb]

Sketcher B-splines cannot (yet) be defined to go through certain points. You, however, try doing it with Draft splines. You may first have to create DatumPoints lying on the curves and the planes.

[mrdic]

I find that drawing D-wires/polylines and converting them to splines makes interpolated splines efficiently.

[codeborg00]

Thank you for your replies.

I used the draft workbench after having calculated the necessary datum points. It all seemed to work fine, however, for some reason, I have come across the issue that my b-splines are not symmetrical along the z-axis (I have attached a screenshot). I was wondering if there is any easy fix for this.

Screenshot from 2022-01-27 20-20-13.png (18.8 KiB) Viewed 1849 times

Thank you in advance

[TheMarkster]

I think this would move the object so it's center of mass is on the origin.

Select the object, press Ctrl+Shift+P. In the python console enter:

Code: Select all

obj.Placement.translate(obj.Shape.CenterOfMass *-1)

If CenterOfMass doesn't work try CenterOfGravity.

[codeborg00]

Unfortunately,

Code: Select all

obj.Placement.translate(obj.Shape.CenterOfMass *-1)

doesn't seem to be doing anything for me. Neither does

Code: Select all

obj.Placement.translate(obj.Shape.CenterOfGravity *-1)

.

[TheMarkster]

Install MeshRemodel workbench. There is a tool there that can be used to make a bspline though selected points. It actually creates a Draft bspline.

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Snip macro screenshot-72c074.png (56.59 KiB) Viewed 1713 times

[thomas-neemann]

...I was wondering if anybody has a solution to my problem.

...

I don't know if it's a solution for you, it's not a b-spline either, but it's in the sketcher.


https://www.youtube.com/watch?v=M7JkL6sAuA0

phpBB [video]

OS: Ubuntu 20.04.1 LTS (XFCE/xubuntu)
Word size of FreeCAD: 64-bit
Version: 0.20.27078 (Git) AppImage
Build type: Release
Branch: (HEAD detached at bcdd926)
Hash: bcdd926686f2245fe60baface1cce1ab3dff7a5b
Python version: 3.9.9
Qt version: 5.12.9
Coin version: 4.0.0
OCC version: 7.5.3
Locale: German/Germany (de_DE)

[thomas-neemann]

... I was wondering if anybody has a solution to my problem.

...

here is another suggestion, with symmetrical, closed bsplines

https://forum.freecadweb.org/viewtopic. ... 49#p566949

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