Curves workbench

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hammax
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Re: Curves workbench

Postby hammax » Mon Dec 16, 2019 11:06 am

… if I design an airfoil in sketcher with 2 BSplines,
and add an IsoCurve via Ruled_Surface, I am getting a collection of profile points.
What is the definition of those Isoline-Points and can they be read out to a database?
Is it something like DiscretizedEdge - I could not find a similar parameter/result there by experimenting?
Maybe this could be used for homemade airfoil data.

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Kunda1
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Re: Curves workbench

Postby Kunda1 » Thu Dec 19, 2019 3:55 pm

Are there official Curves WB tutorials?
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hammax
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Re: Curves workbench

Postby hammax » Thu Jan 09, 2020 6:36 am

… a contribution to the Mixed_curve tool in CurvesWB.
Trying to produce a 3D-"wire" without knot points, Mixed-curve is able to deliver a usable sweep path.
But it only seems to work with Sketcher BSpline. Using a Polyline instead fails - selecting segments is the showstopper.
https://forum.freecadweb.org/viewtopic. ... 97#p358897

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freecad-heini-1
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Re: Curves workbench

Postby freecad-heini-1 » Thu Jan 09, 2020 9:08 am

Chris_G wrote: Ping
Hi Chris,
please watch my video:
https://peertube.mastodon.host/videos/w ... 9f8a5510d0
My wish is to improve the blend curve tool, that it could reference / connect to choosen vertex points.
Or the interpolate curve tool to choose tangent start and end curve, maybe this could be the better choise, because this tool has some nice options in data tab. But it's a lot of work for you, so I'm sorry to bother you.
Best regards
Wilfried
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Chris_G
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Re: Curves workbench

Postby Chris_G » Thu Jan 09, 2020 1:48 pm

Hi Wilfried,
I looked at the video.
I see what you ask for.
This should be possible pretty easily.
I lack free time, but I'll give a try when possible.
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Re: Curves workbench

Postby freecad-heini-1 » Thu Jan 09, 2020 2:29 pm

Chris_G wrote:
Thu Jan 09, 2020 1:48 pm
Hi Wilfried,
I looked at the video.
I see what you ask for.
This should be possible pretty easily.
I lack free time, but I'll give a try when possible.
Hi Chris,
thank you for your fast feedback. Which tool do you mean?
Blend curve or interpolate curve?
Best regards
Wilfried
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Chris_G
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Re: Curves workbench

Postby Chris_G » Thu Jan 09, 2020 2:51 pm

Probably blend curve.
Will_C
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Re: Curves workbench

Postby Will_C » Thu Jan 09, 2020 4:25 pm

Hi guys,

I would have a question regarding a proper workflow for using the Gordon Surface.

I want to create the fuselage of a model plane and used the following Approach:

1) I created a Network of edges with the sketcherWB. The Vertices at the intersections (blue below) are referred to each other via external geometry refernces inside the sketches.
Gordon1.JPG
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2) Using the vetices at the intersections I wanted to create parametrized hulls for the ribs using arches from the sketcher. These ribs shall serve as profiles for Gordon.
Unfortunately even if the segments of these arches are tangential Gordon won't accept them.
So I used bSplines from the sketcher (green below) and aligned the visually to the intersections at the Vertices (blue below).
Gordon2.JPG
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3) Then I created the guide lines for Gordon. Again since segmented edges are not accepted I used a Sketcher BSpline (green below). I distrectized the spline with curvesWB and created a curvesWB Bspline (black below) which I then could snap to the geometriy of my ribs from Step2.
Gordon8.JPG
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This is the only workflow I could manage wich lead to a valid mesh for the Gordon tool. Unfortunately the resulting surface is uneven due to bend interpolated guide lines:
Gordon0.JPG
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Gordon5.JPG
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I assume this is the result from my rib Bsplines from step 2, since the Delta from one rib to the next one is irregular as I drew them manually.
Do any of you have an idea how to solve this issue? I actually am already way above my skills with this one :(

BR,
Will
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microelly2
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Re: Curves workbench

Postby microelly2 » Fri Jan 10, 2020 9:56 am

To avoid these waves the ribs should be perspective equivalent,
there shoud be a perspective transformation from one rib to the other.
what is the inner geometry of the ribs? how many poles you use.
If you have only 4 poles than this should be possible,
otherwise ...
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Re: Curves workbench

Postby Will_C » Fri Jan 10, 2020 12:21 pm

microelly2 wrote:
Fri Jan 10, 2020 9:56 am
To avoid these waves the ribs should be perspective equivalent,
there shoud be a perspective transformation from one rib to the other.
what is the inner geometry of the ribs? how many poles you use.
If you have only 4 poles than this should be possible,
otherwise ...
I reduced the number of poles and it got better. Thank you for the tip.

I'm now using 6 to 7 poles for the geometry of the ribs:
2 for the endpoints.
2 more near the endpoints wit a horizontal constraint to get tangential.
2 to 3 to get the shape of the ribs, which is taken from a plan. If I use less for the shape I won't get the desired curvature.
Gordon9.JPG
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I still have a dent at the ribs because of the guide rails.
Gordon10.JPG
Gordon10.JPG (25.65 KiB) Viewed 221 times
I assume this is due to another issue I also encountered: If I try to use Sketcher arches for the ribs which I discretized with curvesWB and redrew with curves BSpline then I lost the tangential slope when drawing the curvesWB spline.
2nd Picture below Shows sketcher splines with geometry as shown in the first Picture.
1st shows the same sketcher spline but discretized and redrawn with curvesWB
Gordon11.JPG
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So if theres a way to avoid losing the tangential properties of the ribs due to discretizing my Problem would be solved. At the Moment I either have to discretize the guide rails or the ribs in order to snap the intersections for the Gordon mesh.

Might there be a way to set the continuoty during discretization? I saw this menu in the thread but I don't have it in my GUI:
hammax wrote:
Thu Dec 14, 2017 2:14 pm
@Chris_G: some more questions about (sweep_2_rail) <=> Edit: Approximate Points to NURBS.
Working with that tool, one can find some parametrization-options.
- Continuity is almost selfexplaining - are there any recommendations?
- Parametrization grants 4 items - not so clear - a trial and error thing: Any recommendations?
- Smoothing Algorithm - 3 possible Parameters - maybe also a testing and experience thing: Any recommendations?


CWB_Parametr_7.png
And one last question @microelly regarding the transormation tool tutorial https://www.youtube.com/watch?v=UQZCsEjYSTM
At the end of your perspective Transformation tool you showed that if you move your Center poin out of the Frame it will cut your spline.
Does this mean that the parts of the spline touching your target Frame is gone? Or will the spline be aligned to the target frame?

If the later were true that would mean that I can draw a parametric target frame with the desired shape (e.g. an arc made from several segments) and force the bspline to the Frames shape? That would be an amazing Feature.