Another spiral question that's been nagging me: does Illustrator provide any way to create a linear (Archimedes) spiral? I'm trying to create a spiral where the distance between the windings is constant. It looks like Illustrator only makes logarithmic spirals, where the angle of the windings is constant but the distance between grows bigger with each successive winding.
If not, are there third-party plug-ins or solutions of any kind?
I suppose I could write the curve in Postscript, but that seems like work. :)
I cracked this one for you, at least sort of :-)
With the pen tool draw a straight horizontal line. Colour the stroke only. Copy-drag it so that the left end of the copy snaps to the right end of the original line. "Un-colour" the copy.
With both lines selected go to the Distort/Twist filter and enter 360° (or 90°, or 180° - it maketh not much of a diff). Apply the filter as many times as you wish. Now select the uncoloured line and delete it.
I notice however that the line is a bit wobbly in some places (the filter doesn't work very accurately and scatters anchor points here and there along the path), so the line will need a bit of adjustment. Object - Path - Simplify will get you most of the way.
Alternatively (if you're good at drawing with the pen tool), you could make a guide of the original spiral path and use the pen tool to re-trace it smoothly. In which case it would be useful to find the centre of the spiral and snap horizontal and vertical ruler guides to it. That way all your new anchor points will be aligned properly and you can hold down Shift as you drag out the handles.
The trouble with this method is that the spiral gets increasingly inaccurate the more often you apply the filter. Not sure why, but I think it probably has something to do with the positioning of the geometrical centre, which moves slightly each time you apply the filter.
If you apply the Twist filter far too many times you will find that the path sometimes turns back on itself, forming little loops. This shouldn't happen and even Simplify doen't get rid of those loops.
Something is obviously a bit wrong with the way the filter is written.
Here's another way for what it's worth. It corresponds to the old way of drawing a "spiral" with a pair of compasses.
Draw a set of concentric circles with the same increment between sizes. For example 5, 10, 15, 20, 25, 30 units.
Cut and paste the bottom halves of the circles and snap them so that they mis-align by 5 units. Now you've got a double spiral, so you can delete the red bits, Now join up the ends (Join - Smooth) and you've got pretty much what you're looking for. Of course it's not an exact spiral but good enough to fool the eye.
I had a happy accident with Steve Fairbain's first technique. He's right that it's a bit wobbly, but if, after doing the Distort/Twist, you press Cmd-d to duplicate the transform, you get a wave-type Greek key design. Pretty cool!
The Twirl tool produces a decidedly wobbly result much like the Twist filter and very inaccurate near the centre. You can't control the number of turns properly and anchor points get produced more or less randomly it seems. I don't know why these inaccuracies creep in. Seems like accurate Archimedes spirals are a thing that the Illy people haven't addressed properly. The smoothest result so far is my second example, the old "compasses" method, even though it isn't a true spiral.
The Twirl method is indeed a bit wobbly at the center and at the points where the twirl begins on the line. The spacing of the turns seems accurate and even, though. In looking closely at the anchor points and control handles, the ones on the turns are parallel, while those at the center and the outside aren't quite parallel, which is what seems to cause the wobble.
I agree that Illustrator needs a better way to make spirals. I don't use them all that often, but it's frustrating when I do need one.
Here's a shot of another "faux-spiral" done with the "compasses" method. It's easy to construct and completely accurate (see how the stroke widths kiss exactly). Like I said, not a true spiral but good enough for most people and much smoother than anything that Twirl and Twist can do.
The Spiral tool was introduced in Illustrator 6.0, and in those days I think the tool had the capability of making Archimedes spirals.
Here's an image used in the AI 6 User Guide:
The description says "Hold down the Control key to increase or decrease the amount by which each wind of the spiral decreases relative to the previous wind."
In recent versions, that value is a percentage, and I'm thinking that in 6.0 it may have been an absolute value. And Adobe has since disallowed the Control key, so now it does nothing. You can enter the decay rate in the Spiral options dialog, but it has to have a value of 5% or greater.
This method may give a little more control. Here I started with a series of concentric circles, and created a brush which represents only one revolution, which rises the same distance that the rings increase in diameter.
When the concentric rings are stroked with the art brush they combine to create a spiraling effect.
This looks very nice. I haven't tried making a spiral like yours but what is the output like? Do you get a single stroke or is it outlined? If so, I suppose you could delete one edge of the outlined stroke, but it would be nice to know before I start experimenting.
After expanding the appearance, you get one stroke for every concentric circle you started with. You then need to join the endpoints together to get a single path. I noticed that, the farther away you get from the center, the farther apart the endpoints are spaced, but it's very slight.
as Kurt mentioned earlier, the single circle/multiple line brush version is something that has been kicked around on the Illustrator Windows forums: that's where I first saw it.
The single line brush/multiple circle version is my variation of that technique. It has some advantages, some disadvantages.
the 3D version was just a thought. It is actually the most versatile by far if you want fun variations (think spiraling confetti, etc.) and the center is more correct, but it is sloppy in the straight-on view.
All of them break at least once per revolution. The two brush methods wouldn't be too horribly difficult to join if you wanted to do that.