# How to create this pattern?

How can this pattern be recreated? Pay attention that it has round lines in the bottom and straight line at the top.

I tried to use blend tool (in Illustrator) on two arcs and one dot with dotted stroke, but result is far away from original picture.

Trick is to calculate size of arcs, distances, dots frequency, but guys.. there should be another way to to it.

The curve that have stroke = the small circles is an obvious idea. But the whole series of those curves is not Illustrator's blend. It's a series of cutting circles that cut grill's perimetr with evenly spacing (=as the minutes on a clock-face) The angle between the cutters and the perimeter is sharper than 90 degrees to allow cutters to exist above the diameter of the perimeter. A few topmost cutters altough are straight lines to be able to reach high enough.

ADDENDUM: In the following example we construct one curve of holes geometrically. The cutter meets the grill's perimeter circle with 60 degrees angle.

In practice a programmed script should be used. It's straightforward job to calculate the cutters (=centerpoints, radiuses, sectors that remains in the grill area) into an Excel worksheet.

• sounds like it's a spirograph-type of thing where a person can duplicate-rotate circles which are stroked with a dotted kind of dash. – Silly-V Mar 17 '17 at 21:53
• @Pablo the construction of the hole curves is added. – user287001 Mar 18 '17 at 0:50
• Thank you for answer! Could you please explain why do you suggest to use 9 degrees markers and 60 degrees angle for cutters? – Pablo Mar 20 '17 at 12:42
• @Pablo only to keep the image not dense. and the cutting angle well away from 90 degrees (=easy to watch in small size) . 60 degrees can be replaced by anything between plus and minus 90 degrees. The 9 degrees stepping can be replaced by another integral part of 180 degrees.. Actually even this is not a must if we start left-right symmetrically from the bottom. – user287001 Mar 20 '17 at 12:59

Be aware there is an optical illusion taking place due to the shine of the metal making it possibly appear that there are 2 center points in the pattern. There aren't.

What follows is far from perfect I realize. I did not spend a great deal of time in order to precisely figure out blend steps and spacing. But this would achieve the pattern with relative ease. You just have to factor in distance and blend steps more than I took the time to do. In addition, working on much larger shapes helps the transitions a great deal. This answer is to show the overall technique not get you directly to a perfect solution. The end result will take refinement for each use case.

This is merely a blend using a dotted path (with 3 anchor points) and a semi circle with the same dotted path. For the center of the pattern you need a separate blend in order to control spacing.

(Note the straight path has 3 anchors. Just select the path and choose `Object > Path > Add Anchors` to add a center anchor. It needs 3 anchors because the semi-circle has 3 anchors.)

To be honest, the longer the straight path is, the smoother the transition is going to be. For the sake of these screenshots I didn't extend the path as long as I actually would have. The path works better at about twice the length shown here.

Then you create a second blend for the center.

With this in place, you merely add a clipping mask to hide portions resulting in a final "circle: shape. If you need that actual center dot, add that manually.

Because of the transitions you can't really pull this off with a single blend. You get too many steps between the center and not enough on the outside. Not to mention the fact that blending a full circle to a straight path really makes one part of the blend "wonky" because it's got to move from the bottom anchor of the circle to be parallel with the other anchors.

• Some care to explain teh down vote? Is there something incorrect about this? -- And Glad to help @Pablo – Scott Mar 17 '17 at 20:37
• First of all, I'd like to thank you for such detailed answer, I didn't even expect someone can spend so much time on it. Thank you. I did the same way as you in your example, but I don't think it is possible to make it this way. Look at this accurate round edge, even on big sizes masking doesn't show such result - some dots are always sliced. Maybe I'm wrong, will keep testing. – Pablo Mar 17 '17 at 20:39
• Well you may need to expand everything than delete the dots you don't want. And/or the mask may need to be adjusted to move in and out of the dots correctly, a straight-edges circle shape may not work. I posted that I realize my answer isn't perfect because I didn't spend a great deal of time perfecting everything. It was to show the technique, not necessarily provide a 3 click solution. It will need refinement to fit any given situation. – Scott Mar 17 '17 at 21:31
• Can you edit this to show a possible clipping mask? – curiousdannii Mar 18 '17 at 3:00