Drawing with bezier curves

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octosup
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Joined: Sun Jan 01, 2012 12:04 am

Drawing with bezier curves

Postby octosup » Sat Jan 07, 2012 7:50 am

How do you draw with the pen tool? Do you know a good method?
For the sake of simplicity, let's say that you are not drawing from fantasy, but already know exactly what kind of lines you want to create (for example, you are manually tracing a bitmap image). I would like to know if there is a way to obtain exactly those lines only with the pen tool, without having to switch to the node tool. How do you decide where to put placement points and control points?

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brynn
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Re: Drawing with bezier curves

Postby brynn » Sat Jan 07, 2012 4:34 pm

Hi octosup,
If you click + drag when placing a node, it will automatically place a smooth node. And if you keep dragging, you can shape the curve. However, I've personally never found a way to control it. I think some people, who must have incredible hand-eye coordination, are able to control it. But I think most Inkscape users cannot. I suspect that graphic tablet users are able to achieve better control over this.

You might be able to use the Pencil tool, and just draw like a regular pen or pencil. Personally I haven't found a good combination of settings with the Pencil, to do this successfully either.

I actually use the Pen tool in straight line mode, then I can place the nodes precisely and quickly, and not worry about accidentally dragging and creating a smooth node where I might not want one. And then I switch to the Node tool and convert the appropriate nodes to smooth and shape the curves with the node handles. I usually try to place nodes at the apex of curves. I have no idea if that is proper or improper, but it's what works for me. Also, I've found that zooming in quite a lot can help me shape the curves more precisely.

Another trick I've found that works pretty darn well in some situations, is to zoom in quite a lot, until I see the pixel squares. Then I place nodes, again, in straight line mode, at the apex of curves, and over the pixel whose color is half between the darkest and lightest of the line I'm following (or over the darkest pixel, if it's like a black line on a white background). Then when I zoom back out, even though I used straight line mode, I've placed so many nodes, at what appears to be only the slightest suggestion of a curve, it actually looks like a line that follows the curves absolutely precisely, at 100% zoom. If it ends up to be obvious that they are straight line segments, I use Ctrl + A to select all the nodes, then change all to smooth. Then the line is just about 99% perfect! With this technique, the more nodes I place, the better the line fits the curves. Of course if you're working on a large project, the additional nodes contribute to performance issues.

I could make you a screenshot to illustrate, if my description isn't quite clear enough. And I guess others might have some different tricks too?

octosup
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Joined: Sun Jan 01, 2012 12:04 am

Re: Drawing with bezier curves

Postby octosup » Sat Jan 07, 2012 7:52 pm

Thank you very much Brynn! Your description of the technique is very clear, in fact I'm going to have fun with it asap.

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brynn
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Re: Drawing with bezier curves

Postby brynn » Sun Jan 08, 2012 12:59 am

You're welcome!
Lol, yeah it seems that many people avoid node editing, but I quite enjoy it :D

octosup
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Joined: Sun Jan 01, 2012 12:04 am

Re: Drawing with bezier curves

Postby octosup » Sun Jan 08, 2012 2:13 am

brynn wrote:Lol, yeah it seems that many people avoid node editing, but I quite enjoy it :D


Oh I'm sure I will enjoy node editing too :)
At the moment there is so much new stuff to discover that what I end up using or avoiding is often a matter of chance.

The fact is, I've always been unable to draw with pencil and paper, so when I discovered bezier curves I started to flirt with the weird dream that I could learn to draw directly with it... but switching to a more practical mindset, I realize that skill in drawing is not about being able to hold a pencil with great skill, and skill in drawing with the pen tool will probably mean learning to draw first anyway, and then acquiring an eye for bezier curves on top of this.


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