[Solved] Draw Bezier curve with several segments

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David.P
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[Solved] Draw Bezier curve with several segments

Post by David.P »

Hi Forum,

I am trying to draw a smooth Bezier curve with several segments. Unfortunately I only succeed in drawing one smooth segment at a time. A second segment and all other segments do not follow the previous segment smoothly, but each form an acute angle with the previous segment.

Thanks for a tip or a tutorial on how to do this!
Last edited by MrProgrammer on Thu Aug 13, 2020 4:24 pm, edited 1 time in total.
Reason: Tagged ✓ [Solved]
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John_Ha
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Re: How to draw a Bezier curve with several segments?

Post by John_Ha »

See page 196 and following in the Draw Guide.
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David.P
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Re: How to draw a Bezier curve with several segments?

Post by David.P »

Sorry, the Draw Guide I found only has 115 pages:

https://www.openoffice.org/documentatio ... wGuide.pdf

Can you point me to a link?
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Lupp
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Re: How to draw a Bezier curve with several segments?

Post by Lupp »

Using a LibreOffice you should also refer to LibO guides. The most recent LibO Draw guide I can point to is based on LibO V 4.3. but there shouldn't be many changes since: https://documentation.libreoffice.org/a ... wGuide.pdf You find something about Bézier curves there starting on page 227.

The overview concerning LibO guides you find here: https://documentation.libreoffice.org/e ... mentation/.
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David.P
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Re: How to draw a Bezier curve with several segments?

Post by David.P »

Thanks Lupp,
Lupp wrote:You find something about Bézier curves there starting on page 227
However, that's basically the knowledge where I came from originally, since also that LO PDF guide doesn't seem to add much to the online help regarding Bezier curves -- at least not with more than 2 points.

Thanks heaps for any way how to draw smooth Bezier curves with multiple (i.e. many) points :o
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Lupp
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Re: How to draw a Bezier curve with several segments?

Post by Lupp »

Just a question in return: Did you use the toolbar "Edit Points"?

I am not an experienced user of Bézier curves, and there is a lot (in fact most of all) I don't know about them. In specific I cannot create a Bézier curve without starting with two points and a basic curvature and then adding additional points one by one and using the tools "Smooth Transition" and "Symmetric Transition. To explain the working of these tools we surely would need to understand the respective algorithms in detail. For me it's handiwork and eye-judgment only what I can use to get what I want. Sorry.
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David.P
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Re: How to draw a Bezier curve with several segments?

Post by David.P »

Yes I tried and used that toolbar the way that you describe it.

Honestly, if this should be the only way to draw smooth Bezier curves with multiple points in OO/LO, this would be terribly bad in comparison to basically every decent, contemporary drawing software.

Sorry, I sincerely hope that I'm wrong and that there is another, straightforward way.

Edit: Phew, there IS a way, and this guy has totally figured it out:
https://youtu.be/g1orlVkgGRU?t=163
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David.P
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Re: How to draw a Bezier curve with several segments?

Post by David.P »

For completeness, and as a friendly suggestion to the developers, if applicable, I'd like to mention that creating, editing and refining perfectly smooth Bézier curves in P*werP*int is about ten times easier than in OO/LO -- even for me, who has been working with vector graphics programs for decades :o
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Re: How to draw a Bezier curve with several segments?

Post by John_Ha »

Do a google search for bezier curves - there are many tutorials on how to work with them.

Many CAD packages have Bezier curve generators.

Why use a Bezier curve? Splines are very easy to control - see (the free) LibreCAD Spline tutorial 1 for how to create smooth curves from control points. The dolphin starts as the straight lines on the left (Degree 1) and Degree 2 and Degree 3 smooth it as shown.
spline.gif
Dassault Systemes (they write CATIA which is used worldwide for car design) DraftSight has very easy to use splines.
Last edited by John_Ha on Mon Feb 10, 2020 4:54 pm, edited 1 time in total.
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David.P
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Re: How to draw a Bezier curve with several segments?

Post by David.P »

Thanks.

I know how to work with them -- and have done so, occasionally, for 30 years.

Only was going to politely mention that, of all things, MS P*werP*int (same with MS W*rd) is the benchmark to beat here regarding ease and intuitiveness of use
Last edited by David.P on Mon Feb 10, 2020 5:09 pm, edited 1 time in total.
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Re: How to draw a Bezier curve with several segments?

Post by John_Ha »

David.P wrote:MS P*werP*int (same with MS W*rd) is the benchmark to beat here regarding ease and intuitiveness of use
It depends on what you are trying to achieve.

Word and PowerPoint are aimed at producing something page or poster size which looks pleasing to the eye. This is is pretty trivial.

Car bodywork is infinitely more demanding as you have very long surfaces where you have to work to tight manufacturing tolerances and where a deviation not detectable to the human eye throws up awful ripples and lines when illuminated. Just look at the reflections in a skyscraper's supposedly flat - it's all float glass - windows and you see ripples and distortions everywhere. You need very powerful control methods to specify both location of points and slopes of curves in three dimensions and to blend the curves seamlessly.
Last edited by John_Ha on Mon Feb 10, 2020 5:03 pm, edited 1 time in total.
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Remember: Always save your Writer files as .odt files. - see here for the many reasons why.
David.P
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Re: How to draw a Bezier curve with several segments?

Post by David.P »

Car bodywork in three dimensions is definitely NOT the target use of OO/LO draw
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Re: How to draw a Bezier curve with several segments?

Post by RoryOF »

But, John's third dolphin looks very like the AirBus Beluga XL.

https://i2-prod.bristolpost.co.uk/incom ... uga-xl.jpg

Thank God someone in the Airbus paint department has a sense of humour!
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Re: How to draw a Bezier curve with several segments?

Post by John_Ha »

It's predecessor was the Guppy and Super Guppy, both as improbable as Beluga. One wonders how they fly and I am sure Wilbur and Orville Wright would be astonished.

I frequently saw them at BAe Filton where the Airbus wings are made.
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guppy.jpg
LO 6.4.4.2, Windows 10 Home 64 bit

See the Writer Guide, the Writer FAQ, the Writer Tutorials and Writer for students.

Remember: Always save your Writer files as .odt files. - see here for the many reasons why.
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