Circle and arc tool

[Michael Brown12]

I'd like to see a true circle and arc tool. As it is now, AI only draws polylines that look like circles or arcs.

Before anyone gets upset, let me say I KNOW that AI draws circle-shaped and arc-shaped polylines. That is not what I'm talking about. A circle is defined as a set of points the same distance from a center point, its radius. It is manipulated by changing the radius, diameter, circumference, or a combination. It is not defined by its x,y dimension.

It is worse for arcs, however. it would be nice to be able to define a center point, start point, end point and/or the included angle. It is much easier to draw an arc if you can start at the center, drag out to the radius and drag the arc as you want. It would also be nice to construct arcs using three points or a chord. Again, arcs are never defined nor drawn using the x,y space they cover.

The ability to alter shapes by their true definitions, rather than crude x,y dimensions, would be really helpful. What is good for a squares and lines is not always good for circles and arcs. Thanks.

MGuilfoile

[JETalmage]

M,

I agree with the request for a better ellipse tool, and for a proper arc tool instead of the practically useless one AI presently has. (They should both be combined in a single tool, as in FH and Draw.) However:

> Before anyone gets upset, let me say I KNOW that AI draws circle-shaped and arc-shaped polylines.

Describe exactly what your definition of a "polyline" is.

AI, (like FH) neither draws "polylines" nor "circles." It draws Bezier paths. Circular paths are approximated by four Bezier paths.
It does not necessarily follow, just because the interface prompts the user for height and width (which I agree is lame) for an ellipse, that the program is using whatever you mean by "polyline" as its drawing method.

For example: I have an AI Javascript which lets me call for an ellipse the way a drafter would: in terms of major diameter and "angle". (Ex: a 1" 35 degree ellipse.) That doesn't mean the actual way AI draws the resulting path is any different. (It isn't; it's still just drawing four Beziers.) My Javascript just effectively provides a different interface.

Another example is a Javascript that lets one define an equilateral polygon by its side length, instead of its "diameter". Again, there is nothing different about the actual math AI uses to draw the resulting path. Illustrator is still just drawing Bezier curves; I've just injected a multiplication factor.

Similarly, AI's ellipse dialog could (and should) also provide different sets of user inputs for specifying the desired ellipse or arc. (Ex: Radius, Arc, start angle, end angle.) Adobe owns FreeHand's better treatment and could similarly replicated it in AI; were it not for AI's still not providing live geometric shape primitives.

> A circle is defined as a set of points the same distance from a center point, its radius.

Yes, that's the definition of a circle. By that definition, Illustrator couldn't draw one if it wanted to. Your monitor displays a rectangular array of pixles. A printing device renders a set of fixed printer spots. Neither of those conform to the definitive requirements of "a circle."

So even programs that do provide the dimensional inputs you desire (ex: Draw, Canvas, FreeHand, CAD programs) effectively draw what I think you are calling a "polyline"--the curve is aproximated by a set of straight line facets which are, in turn, approximated by lighting up the nearest monitor pixels or printer spots or plotter stepper motor increments. (Anyone who has ever imported a DXF into Illustrator has seen this.)

> It is manipulated by changing the radius, diameter, circumference, or a combination.

Now you're talking about manipulation, not definition. Manipulation is interface. It has nothing to do with whether AI constructs the ellipse and arc with Beziers or with other curve definition math. It's just a matter of what inputs you want to provide the user.

> It is not defined by its x,y dimension.

Now you're talking about definition again. No, a height value and a width value do not define a circle. But those values can be employed as the user inputs for scaling the results of a math algorithm that generates curves--whether that math is Bezier, or whether it's something else you call "polyline."

This is just one example of what I'm taking about when I charge that these so-called "illustration" programs are really mere page design programs. They don't allow the illustrator to think like an illustrator; they tyrannically force the illustrator to reference everything to the vertical and horizontal edges of the page, rather than the construction axes of his actual drawing.

But it doesn't have to be that way, just because AI constructs curves by Beziers.

JET

[Michael Brown12]

A polyline is a bunch of lines stuck together end to end. I assumed that AI was creating curves by calculating the individual slopes of a curve cut into sections (taking the derivative of each tiny curve, although my calculus is a little rusty). More resolution was gained by dividing the curve into more pieces. As the length limit went to zero, a better approximation of a curve would result. I don't think it is possible to create a perfect ellipse (of which a circle is a special case) this way, but you can get close. I understand from you that they are not done this way in AI, but use Bezier curves instead. Obviously you are right; all you have to do is look at the AI curve and see the handles and end points. My mistake.

Who said that definitions and manipulations were mutually exclusive topics in a conversation? That is kooky talk. They are tightly tied together.

Mostly, I don't really know what you are talking about here, although I think we agree that AI's arc/ellipse tool is unusable. All I'm asking is that I be able to control circles and arcs via their salient features. I couldn't care less what happens "under the hood" as long as my output data are accurate within a given error range. Thanks, for putting me straight about the polylines, though!

MGuilfoile

[JETalmage]

> Mostly, I don't really know what you are talking about here

M,
Your post seemed to suggest that you thought AI would have to use different curve math from what it uses today, in order to give you the ability to call for a circle in terms of radius, diameter, or circumference. In fact, you stated that with emphasis:

> Before anyone gets upset, let me say I KNOW that AI draws circle-shaped and arc-shaped polylines.

I was just pointing out that such an improvement would not require anything so ambitious as another curve math. It's jsut an interface thing. (And that's why I pointed out the distinction between definition of a curve and the mere interface for calling it.)

As I said, I agree with the request.

JET

[Guest]

I'm currently evaluating AiCS4 and the possibility of migrating from FreeHand MX.

It appears in Ai, it is not possible to adjust an arc or ellipse to an arc angle other than 90 degrees. Is that correct?

Every other vector graphics package I've ever used allowed me to do this. For example, in FH, it's done with an ellipse either by dragging the circle's start or end point or by specifying the start and end angles in the properties dialog. I can even do it in FrameMaker, with its limited native graphics package.

If I can't adjust an arc or ellipse, it's pretty much a deal breaker. I'm not an illustrator by training, I'm a tech writer but I do a lot of exploded views, isometics and such.

Can I erase a portion of an arc or circle with the erasor tool? I've tried that but I can't get it to work.

[Wade_Zimmerman1]

I am certain that Illustrator is the right tool for you though I agree with the OPs request 150%.

http://mysite.verizon.net/wzphoto/Arc.mov

Also

[Guest]

Erasor tool it is. Thanks for the tip, Wade.

I almost don't have a choice with respect to migration. With several thousand FH files, AI is our only practical option. At least CS4 natively opens all FH files. If we had done the migration when FH was officially dead-ended 2-3 years ago, we'd have had to resave most files back to previous versions. I don't see any reason to do the migration until we have to. Maybe future versions of AI will be even more compatible.

[JETalmage]

krygny,

If you need anything even approaching accuracy, I would not recommend using the eraser tool to achieve a circular arc of a given degree. Nor would I recommend using the hideous Arc Tool.

If you need a circular arc, and insist on using the Arc Tool, be sure to doubleClick it and set its Slope setting to 50 or -50. Then, when dragging the arch, press and hold Shift to constrain it to circular.

Illustrator does not have any straightforward arc capability like that of FreeHand's Ellipse tool. So for accurate portions of a circluar arc, you will need to perform manual construction. For one example method:

1. Draw the circle to the required diameter.

2. Locate its center (ex: turn on the Show Center button in the Attributes Palette).

3. Use radii or diameters to locate the desired start/end angle. (Ex: use the Line Tool to draw the radii or diameters, align them to the center of the circle, rotate them numerically as needed.)

4. Cut the circle at the intersections.

There are various other methods, but the point is: Because Illustrator has no proper arc tool (or corresponding intelligence in its Ellipse Tool), you have to construct a numerically-accurate arc by some workaround method. You can't just enter start and end angle values like you can in FreeHand.

There are several workarounds you can devise to facilitate drawing in isometric. One example is to construct an "isometric protractor" and store it as a Symbol. Alternatively convert it to a set of PathGuides and lock/unlock Guides to move it around as needed.

For example, you can build an isometric protractor with ticks at 10° increments by:

1. Radial Grid Tool: Click. In the resulting dialog, make height and width equal. Set Concentric Dividers to 0. Set Radial Dividers to 36. Click OK.

2. DoubleClick the Scale Tool. In the resulting dialog, set vertical scale to 57.7%; horizontal scale to 100%.

3. Rotate 2 copies of the figure 120° to have a protractor for each of the 3 iso axes.

JET

[ReactionAtWork]

This is truly horrifying. Am I to understand that it is not possible to set a start angle and end angle when drawing a circular arc in Illustrator?  If so, then my company has just wasted $x000 on CS4, because I use arcs like this on a daily basis. I assumed that something so utterly, stupidly, primitively simple as this would be guaranteed to be in Illustrator!  We thought we were upgrading from CorelDraw Suite12, ensuring our future by going with the "industry standard" Illustrator. But if it is not possible to draw a precise circular arc numerically, then I'm utterly stuffed.  Awkward Bezier curves are of little use to me, but it seems that under the skin, Illustrator is entirely Bezier-based when it comes to drawing arcs, curves, straight lines or anything else!

I wish we'd bought the latest Corel Draw suite now, since it costs a small fraction of the price and has all it's drawing tools properly worked out - including a combined Ellipse / Arc tool that's incredibly simple to use....  I'm going to go and lie down and quietly tear my hair out!

[Wade_Zimmerman1]

I think many people expect Illustrator to be a CAD program and a

technical illustration program etc and do not realize though

Illustrator is often used and preferred for this type of work it is

rely a creative tool

for creating creative art, design and visuals.

However if you select the arc tool, admittedly not the most advanced

tool there is, and click in the document window once the arc tool

dialog will pop up offering some settings you might find you can use

to assist you to do what you want to do. This tool is long over due

for a overhaul since so many users like yourself seem to like the idea

that Illustrator is the application they would like to use for this

purpose.

And in doing so they may add other shape creating features like

adjusting individual round corners on a shape.

A triangle tool so you can create triangles with numerical value input.

May never happen.

[ReactionAtWork]

What is more absurd is that Adobe Flash has a Start Angle and End Angle option clearly available for its Oval Primitive tool. When I saw that in Flash, I went straight back to Illustrator to look for the same tool... and I thought that all the CS4 programs were supposed to be harmonized!  The lack of a proper Arc tool is both breathtaking (since Illustrator has been around for SO long) and hugely important for my work.

Thankfully, the method described by JETalmage above provides a slow, cumbersome way of creating the required arc, so I'll have to look into the possibility of scripting the process (I've only had CS4 for a week so this is probably impossible too ) or creating a library of ready made arcs.

NB: Why shouldn't an "artist" want to include some proper circular arcs in their work?  If I'm designing company logos that consist mainly of stylized text, I'm frequently going to need accurate arcs for the outlines of my custom letter shapes. It is inexcusable that this tool isn't available, especially when Corel Draw has had it for as long as I can remember (back in the early 1990's!)

[Wade_Zimmerman1]

However many users of Flash use Illustrator since Flash is limited in

what you can do in the way of Illustration so where it has some tools

Illustrator does not have it can do so much more in other ways.

[ReactionAtWork]

I was using Flash to start with, but when found its drawing tools a bit limited I moved back to Illustrator to create my artwork (with the intention of also testing the possibilites of importing Illustrator art into Flash and then animating various objects). That's when I discovered the missing Arc functionality in Illustrator 😉

Using JETalmage's method described above, I'm now manually creating a set of ready-made arcs from 5 degrees to 355 degrees in 5 degree increments, so the issue won't slow me down in the future.

[JETalmage]

Am I to understand that it is not possible to set a start angle and end angle when drawing a circular arc in Illustrator?

Yep. Read it and weep. Or at least roll your eyes at the absurdly laughable defensiveness of devotees to this ridiculously archaic program. "Illustrator isn't supposed to be a CAD program; Illustrator is for paper doilies." (As if there's something particularly technical about drawing a circular arc.)

If so, then my company has just wasted $x000 on CS4, because I use arcs like this on a daily basis. I assumed that something so utterly, stupidly, primitively simple as this would be guaranteed to be in Illustrator! We thought we were upgrading from CorelDraw Suite12

Never assume. Try out the program before you buy it. There are alot more people riding 4 wheelers than trials bikes. That doesn't mean a 4 wheeler isn't a lumbering oaf by comparision.

ensuring our future by going with the "industry standard" Illustrator

An industry can have pretty low standards.

Awkward Bezier curves are of little use to me

Nonsense. CorelDraw creates Bezier Curves, too. Again, it's just a matter of interface. FreeHand, Corel Draw, Canvas, et al enable the user to draw a Bezier curve in the shape of a circular arc in interface terms of angles and radius. It's not Bezier curves that prevent that in Illustrator. It's just poor interface design.

Illustrator is entirely Bezier-based when it comes to drawing arcs, curves, straight lines or anything else!

Every PostScript program is, including CorelDraw. There's nothing wrong with Bezier curves. They are in fact superior in many ways to the kind of splines CAD programs usually create. (Bezier himself was a mechanical engineer.) Don't foo-foo Bezier curves on the basis of Illustrator's hideous interface and archaic feature set for drawing and manipulating them.

I'm going to go and lie down and quietly tear my hair out!

Over this? Egads, man, I hope they don't let you play with sharp instruments. You're sure to do yourself serious harm when you find out all the far more important things Illustrator is lacking.

JET

[Eddie Ostrowski]

Haven't had the heart to part with my Lietz Ellipse Templates just yet.

Eddie

[Guest]

Eddie Ostrowski wrote:

Haven't had the heart to part with my Lietz Ellipse Templates just yet.

Eddie

... and your horse-hair brush? 🙂

[ReactionAtWork]

I've posted a link to a file I created containing circular arcs from 10 degrees to 350 degrees in 10 degree increments (the link's on the online Illustrator help page for "Arc tool"). The file also shows how to create your own custom arcs (thanks to JETalmage). Hopefully other poor newbies will go to that page and immediately find the answer they need, before they waste half an afternoon (like I did) searching for that hidden Arc tool panel that doesn't exist!

[dissidently]

Guess the version a real arc tool shows up....

My money is on 2024, at this pace.