cutting/segmenting a spiral?

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paulbeard
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Joined: Thu Jul 11, 2019 2:57 am

cutting/segmenting a spiral?

Postby paulbeard » Thu Jul 11, 2019 3:02 am

Is a way to cut up a spiral into defined segments, besides duplicating it and measuring each iteration? If I have a 24 inch spiral I want cut at 4 inch intervals, is there a way to do that?

tylerdurden
Posts: 2292
Joined: Sun Apr 14, 2013 12:04 pm
Location: Michigan, USA

Re: cutting/segmenting a spiral?

Postby tylerdurden » Thu Jul 11, 2019 5:50 am

I'd try using the LPE (Menu: Path>Path Effects), Pattern along Path.
    Make a segment 4" long, and copy it.
    Apply the LPE to the spiral.
    Select repeated, not stretched.
    Click the paste button in the LPE dialog.
Have a nice day.

I'm using Inkscape 0.92.2 (5c3e80d, 2017-08-06), 64 bit win8.1

The Inkscape manual has lots of helpful info! http://tavmjong.free.fr/INKSCAPE/MANUAL/html/

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ragstian
Posts: 1181
Joined: Thu Oct 11, 2012 2:44 am
Location: Stavanger-Norway

Re: cutting/segmenting a spiral?

Postby ragstian » Thu Jul 11, 2019 5:09 pm

Hi.

Great tip!

It would be nice if the abbreviations is spelled out completely first time used.
For a beginner the letters LPE is just a group of “random” characters that don’t make any sense.
If we spell out completely like this: LPE (Live Path Effects) the letters make more sense.

The “improper” use of abbreviations is very common,
if we reflect about our audience we will most likely get
to the conclusion that they span from absolute beginners to advanced users.

Let’s make it easy for the beginners.
Good Luck!
( ͡° ͜ʖ ͡°)
RGDS
Ragnar

tylerdurden
Posts: 2292
Joined: Sun Apr 14, 2013 12:04 pm
Location: Michigan, USA

Re: cutting/segmenting a spiral?

Postby tylerdurden » Sat Jul 13, 2019 4:04 am

The interpretation of the abbreviation was left as an exercise for the reader. Particularly since the directions explicitly indicated where in the menus the operation was to be found.

If we prefer to nitpick, we might observe that the term "Live" is likely deprecated, since it does not appear in the UI (and is mostly used by crusty veterans).
Have a nice day.

I'm using Inkscape 0.92.2 (5c3e80d, 2017-08-06), 64 bit win8.1

The Inkscape manual has lots of helpful info! http://tavmjong.free.fr/INKSCAPE/MANUAL/html/

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druban
Posts: 1818
Joined: Fri Nov 20, 2009 10:48 pm

Re: cutting/segmenting a spiral?

Postby druban » Sat Jul 13, 2019 5:45 am

I was tinkering to see if there was a stroke method to do this and came up with these little lovelies. Lazur, you probably know what they are called mathematically etc. It seems like the kind of thing you are an expert on! But I just like to stare at them at length very likely as a result of ingesting many things I was warned not to. :twisted:

spirals.png
spirals.png (115.41 KiB) Viewed 100 times
Attachments
spirals.svg
(109.39 KiB) Downloaded 5 times
Your mind is what you think it is.

Moini
Posts: 3244
Joined: Mon Oct 05, 2015 10:44 am

Re: cutting/segmenting a spiral?

Postby Moini » Sat Jul 13, 2019 7:49 am

It's more the term 'Path' in LPE that Jabier wants to deprecate, because it's no longer limited to paths. However, Inkscape has registered a trademark for it, so it's going to stay for a while.
Something doesn't work? - Keeping an eye on the status bar can save you a lot of time!

Inkscape FAQ - Learning Resources - Website with tutorials (German and English)

Lazur
Posts: 4694
Joined: Tue Jun 14, 2016 10:38 am

Re: cutting/segmenting a spiral?

Postby Lazur » Sun Jul 14, 2019 7:41 am

druban wrote:Lazur, you probably know what they are called mathematically etc.

spirals.png


Tricky question.

With the divergence of 1 those spirals are Archimedean spirals.

If the divergence was higher, they would be logarithmic spirals.
The overlayed dash pattern along the path describe perpendicular line segments, which could resemble curves that are perpendicular to the spirals. On logarithmic spirals they are also logarithmic spirals.

In this case with Archimedean spirals, the tangent curve may also be somekind of Archimedean spiral, although my guess that's harder to prove.
But what we see in that image is more of an interference pattern.
With each turn on that spiral, the length grows in a linear manner. In a non-polar coordinate array a very similar effect could be experienced if there were parallel lines above eachother with the same dasharray, but with each row the offset of the pattern would increase linearry.
From that point of model you can see if the dasharay is adjusted you can end up with a pattern that hardly resemble any "offset" between the spiral's turns and showing a radial pattern. Or end up with a pattern that seem to "rotate" backwards.

Oh well this could be a trippy experiment with animating dasharrays to see how the stroke dash/gap sizes affect the output.

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druban
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Joined: Fri Nov 20, 2009 10:48 pm

Re: cutting/segmenting a spiral?

Postby druban » Sun Jul 14, 2019 7:44 am

Simply animating stroke width changes the pattern. Don't get sucked in!
Your mind is what you think it is.

Lazur
Posts: 4694
Joined: Tue Jun 14, 2016 10:38 am

Re: cutting/segmenting a spiral?

Postby Lazur » Sun Jul 14, 2019 8:47 am

Not the width (and not the bees for that matter) but the stroke-dasharray, like in Moini's extension.
Keeping the same stroke-dash ratio while altering their sum manually until they reach an amount (like twice as the starting value preferably) and back.


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