3

I want to do this

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But when I zoomed in I got this

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This is problematic because I need to cutout some of intersecting are using shape builder tool. Some intersection is not cut while other leaks.

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I am going to intersect tons of circles because I am making a golden ration(ed) logo, instead of tracing it down. If I don't fix this kinds of thing ASAP I get this

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Now I had to redo everything after I am waiting for answer.


BTW I KNOW THIS

Disable Allign to Pixel Grid from Transform Menu

And CTRL + DRAG TO ALLIGN THE CIRCLE

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Apparently, this do not work too. If I zoom in deeper it is still misaligned.

enter image description hereenter image description here

WHAT I WANT IS MAKING A CIRCLE WITH THE CENTER (A) and INTERSECT POINT (B) [CTRL+CLICK at A DRAG to B and have it intersect B automatically] without adjusting it afterwards because I will then have to move the center (A) slightly to the left which I something I do not want.

enter image description here

  • Would you consider using another tool that can export to Illustrator for finishing up? Interactive geometry tools like GeoGebra are designed for doing this sort of thing easily. – smithkm May 26 '17 at 0:22
  • I have thought about that, but really what I wanted to do is using proper semantics when designing a logo inside Illustrator ex: basic shapes intersection instead of manually tracing it, but it didn't work so smoothly. It is an option yes. – LordSacha May 26 '17 at 10:44
5

There is a trick to accurate circles

If you want accurate circles, then do not draw them with by dragging the ellipse tool. It is not a circle tool (you can get one here). Using ellipse tool like this would be way too inaccurate. Instead what you do is you draw a line that represents your radius. Then measure your line and alt click on the point you want the center to be at and TYPE in the radius.

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Image 1: When you alt click you get a dialog to type the accurate radius you measured with the line tool

This is way more accurate, and it is even more accurate in illustrator CC (since you can get more digits on the line)

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Image 2: If you want accurate circle intersections TYPE the radius from meaurement

If you want to find intersections between other things, same thing applies except that you need to use smart guides on your circle.

Since this can get boring to do over time Ive written a script that will draw a circle if you draw the radius line (since i can not always install subscribe):

var sel = app.activeDocument.selection;
for(i=0; i<sel.length;i++){
   var pts = sel[i].pathPoints;
   var radius = Math.sqrt(
          Math.pow(pts[1].anchor[0]-pts[0].anchor[0], 2)+
          Math.pow(pts[1].anchor[1]-pts[0].anchor[1], 2)
          );

    app.activeDocument.layers[0].pathItems.ellipse( 
        pts[0].anchor[1]+radius, 
        pts[0].anchor[0]-radius, 
        radius*2, radius*2);
}
  • Whoa. Never thought about resorting to script. This is so far easiest trick without resorting to manually lining up the the arc. Thanks! – LordSacha May 25 '17 at 17:57
  • 1
    @LordSacha yes, that's because you are trapped in the GUI land. Pretty normal. – joojaa May 25 '17 at 18:07
  • I know the logic behind this, but I tried to make a line. Use that as radius. Checked the length, duplicate it to be diameter just in case. Made a circle with radius*2 = diameter. Placed center of circle in intersection of the two radius line I drew. For some reason, the circle is slightly too big when zoomed max. Very confused – LordSacha May 25 '17 at 18:54
  • Nevermind it suddenly fits perfectly.. o.O – LordSacha May 25 '17 at 18:56
  • @LordSacha Well, a rational Bézier curve, as used by illustrator, can NOT make a perfect circle. You can only get so close. So if you really want even remotely mathematically accurate circles you would need to use some other application. Although i could rotate the circle or make a 8 paoit circle instead for more accuracy. – joojaa May 25 '17 at 19:01
3

I do not blame you for wanting this to be better. Lord knows there are times I wish Illustrator was better at this. My answer is not meant to convey a sentiment that you are incorrect in your workflow or methods in any way, but merely explain why things aren't as you want them to be in terms of snapping.


Unfortunately paths of circles won't align to anything automatically themselves. Arcs are a difficult thing for Illustrator to align mid-path. Only the anchors along the circle's path offer any sort of real snapping. In other words, you won't get "a circle to intersect with other paths automatically". You can only get the anchors along a circle to snap or other paths to snap to the circle.

You can turn on Smart Guides (View > SmartGuides) and that will offer some snapping to the circle paths when drawing other paths. So, drawing a path you want as an intersect with the arc of a circle will snap the arc with Smart Guides enabled.

In addition to disabling Align to Pixel Grid, you may or may not want to enable/disable Snap to Point (View > Snap to Point) as well. If your circle arc happens to not be crossing an exact point, and Snap to Point in enabled, then your end anchor may not rest along the circle precisely. With Snap to Point disabled and Smart Guides on, you should be able to draw a path and have it snap to the arc of the circle.

The issue here...

enter image description here

.. is you are expecting Illustrator to align an anchor on the intersection of two arcs. Illustrator doesn't calculate that intersection. It calculates the arcs individually from their anchors, so it can snap to each arc, but illustrator doesn't see that intersection as a snap point. You have to manually ensure things align in such instances.

In short....

  • Snap Paths to circle arc = yes
  • Snap circle arcs to paths = no
  • Snap path to multiple circle arcs = no

On the whole, Illustrator isn't always a precision tool like a CAD application would be. It's a drawing tool first, precision if kind of an afterthought in many areas. While it attempts to be precise, there are times when you need to use other features such as View > Outline or Object > Path > Average to get anchors to precisely line up. Depending on your goal, it is often necessary to take that extra step to align things. I don't fully understand the apparent issue with that. Precision takes a bit of extra work, as it does in any application.

If the goals is absolute precision, I'd suggest you work in Outline mode entirely for the set up. The strokes on paths can easily cause you the think something is aligned when it isn't whereas in Outline mode, you just see the actual paths.

  • Yep I understand. No need to be afraid of hurting my feelings. With that prologue, I think you over calculated my age a lot LOL. You won't believe how -old- young I am. I don't what magic designers in Youtube use, but I seems they can snap stuff so easily and use shape building tool like nothing. Anyway, thanks for pointing out the outline mode. Never thought about that before. Thank you very much! – LordSacha May 25 '17 at 17:52
  • @LordSacha it's been stated that I can come across, unintentionally, rather "blunt" in my answers. Just trying to circumvent that a little :) – Scott May 25 '17 at 18:01

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