Curves workbench

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Vincent B
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Re: Curves workbench

Post by Vincent B »

A smooth surface with continuity could be like this. But you should avoid sharpened corners, the loft doesn't like too much.
Attachments
Capture2.JPG
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sweep2rail.FCStd
(892.69 KiB) Downloaded 29 times
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hammax
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Re: Curves workbench

Post by hammax »

... why doesn't work Blend_Surface between those shells?
A Gordon surface with additional frame-lines is possible.

BlendSurface.PNG
BlendSurface.PNG (54.35 KiB) Viewed 2112 times
Attachments
Blend_Surface.FCStd
FC.19.3 a working example
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RG65_NACA16012_8.FCStd
FC.19.3
(210.71 KiB) Downloaded 30 times
Last edited by hammax on Mon Jan 24, 2022 5:38 pm, edited 1 time in total.
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Sabm01
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Re: Curves workbench

Post by Sabm01 »

Vincent B wrote: Thu Jan 20, 2022 8:00 pm A smooth surface with continuity could be like this. But you should avoid sharpened corners, the loft doesn't like too much.
Thanks Vincent for the advise.
As you see the sweep surface joint only 2 curves. So I have 3 surfaces. It would be desirable to obtain one single surface pour the total conduit to have a better continuity of tangences. I tried but it does not work properly. The points generated overshout the limits of the curves at ends of the conduit.
Is it because it is not yet implemented or a misuse from me?

Michel
Michel Sabourin (Sabm01)
www.simturb.com
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onekk
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Re: Curves workbench

Post by onekk »

Vincent B wrote: Thu Jan 20, 2022 8:00 pm A smooth surface with continuity could be like this. But you should avoid sharpened corners, the loft doesn't like too much.
Usually matching number of segments of the two edges will help to loft digest things, for stright segments, it would be trivial to "discretize" the edge with sharp corners, with the same number of segments of the other edge, or maybe discretize both and recreate a wire and a curve (B_spline, Bezier, or some other curves) with same "segment counts".

It is not possible in every case, but in some case it has helped.

Regards

Carlo D.
GitHub page: https://github.com/onekk/freecad-doc.
- In deep articles on FreeCAD.
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Chris_G
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Re: Curves workbench

Post by Chris_G »

hammax wrote: Mon Jan 24, 2022 12:16 pm ... why doesn't work Blend_Surface between those shells?
A Gordon surface with additional frame-lines is possible.
Because the current blend_surface algorithm uses an offset function that doesn't work on C0 geometry, and the top surface is C0.
I don't like that part of the algorithm (that is not clean and robust IMO).
Good news is that the code refactor I am working on doesn't use this method anymore, and is able to extract the surface data correctly :
Surface_data.png
Surface_data.png (26.59 KiB) Viewed 2041 times
pafurijaz
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Re: Curves workbench

Post by pafurijaz »

Hi @hammax You will probably have your solution for this but nevertheless I wanted to give a try, because I'm studying Curve-workbench and FreeCAD, and it is possible to work around the problem with the blend between curves, here I have created various sections on the two surfaces and I have made the blend between the curves with G3 continuity, and I created a Gordon surface.

Image

Greetings
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RG65_NACA16012_8.FCStd
(880.12 KiB) Downloaded 33 times
m1cha1
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Re: Curves workbench

Post by m1cha1 »

Is it possible to rotate control points of freehand bspline to change the shape? BTW list of the control keys in the Report view it's very helpful
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Chris_G
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Re: Curves workbench

Post by Chris_G »

No, you can't rotate control points.
balrobs
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Re: Curves workbench

Post by balrobs »

Hello,
recently I discovered this amazing workbench while doing some stair design work.
Thanks and kudos to the developers!
My intention was it to map a stair-profile sketch on a curved surface and then to "extrude" it to get a stair model.
I thought that starting from a sketch-frame which has the same dimensions as the surface unwinding lengths would produce equal step lengths. Unfortunately this is not the case.
Is this the way the SketchOnSurface-tool is ment to work? ... and if so is there another way I can acieve my goal.
Hope my description make sense. This is a pic and a file to better explain my issue
Map_Sketch_On_Surface.jpg
Map_Sketch_On_Surface.jpg (71.25 KiB) Viewed 1775 times
Kind regards and thanks in advance for the help :)
balrobs
Attachments
Map_Sketch_On_Surface.FCStd
(43.01 KiB) Downloaded 34 times
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Chris_G
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Re: Curves workbench

Post by Chris_G »

Hello,
Sketch_On_Surface depends on how the target surface is parametrized.
An ellipse is not parametrized by arc-length, so the mapped object is deformed / stretched.
A possible solution is to discretize the ellipse, and approximate it with a uniform parametrization.
This may not be totally accurate, but much better anyway.
Attachments
Map_Sketch_On_Surface_fixed.FCStd
(93.79 KiB) Downloaded 29 times
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