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Answered

Polygon points not exact/not on circle

Forum|Forum|7 years ago
April 4, 2018
2 replies
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Illustrator 22.1 64-Bit, Windows 7

When drawing with the polygon tool inside a circle with the same radius, only one anchor point is exactly on the circle. The others are slightly off inside the circle. The gap is only visible at a zoom of 10000%+.

This occurs both when drawing manually from the center of the circle to any of its anchor points or when entering the radius numerically through the one-click-context- menu. The dimensions of the circle were checked multiple times.

This causes problems when using Pathfinder or geometrically constructing shapes.

This topic has been closed for replies.

Correct answer Jacob Bugge

Adrian,

I am afraid this is owing to the inherent bulging of Bezier circles made with four Anchor Points, which (only) have a true/accurate radius at 45 degrees intervals, at and midway between Anchor Points. The bulging is highest at +/- 22.5 degrees from each Anchor Point.

I believe the fitting polygon Anchor Point is coinciding with a circle Anchor Point.

You may try an adaptation with a tiny increase in the polygon radius which no one will notice without selecting paths at high zoom levels.

Jacob Bugge

Correct answer

Community Expert

Adrian,

I am afraid this is owing to the inherent bulging of Bezier circles made with four Anchor Points, which (only) have a true/accurate radius at 45 degrees intervals, at and midway between Anchor Points. The bulging is highest at +/- 22.5 degrees from each Anchor Point.

I believe the fitting polygon Anchor Point is coinciding with a circle Anchor Point.

You may try an adaptation with a tiny increase in the polygon radius which no one will notice without selecting paths at high zoom levels.

A

adriand89618423Author

Participant

Is there a way to get a true circle in Illustrator?
Increasing the polygon radius does not really help because I need to construct geometrically...

Doug A Roberts

Community Expert

not a true circle, no. you can reduce the inaccuracy to the point where it vanishes in Illustrator's rounding by creating circles out of more than four anchor points.

this is possible by creating a many-sided polygon and rounding every corner point.

or by using the circle script here:

Adobe Illustrator Scripts by Hiroyuki Sato

Doug A Roberts

Community Expert

the massive zoom makes me think that this is due to the (tiny) inherent inaccuracy of bezier-constructed circles.

show the exact nature of the shapes and i'll try and verify.

Jacob Bugge

Community Expert

Hi Doug.

The very last full snow here was early on the first of April, just for a few hours. How there?

Doug A Roberts

Community Expert

https://forums.adobe.com/people/Jacob+Bugge wrote
Hi Doug.
The very last full snow here was early on the first of April, just for a few hours. How there?

nothing locally in April here. A short dusting at the end of march made everything very pretty for a day though.

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