Circle around gadget?

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Onetrack
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Circle around gadget?

Post by Onetrack »

How can I create a circle around a vector, or group of vectors, that works in a similar way to the square around gadget?

The vector in question for me is a 3 sided polygon, but it would be useful for any vector, or group of vectors.

thank you.
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4DThinker
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Re: Circle around gadget?

Post by 4DThinker »

Do want a circle that passes through all the corners, or just minimally encircles the polygon? The former is possible with a simple drafting trick on 3 any sided polygons only as far as I can tell.

4D

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adze_cnc
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Re: Circle around gadget?

Post by adze_cnc »

If anyone's willing to write a "circle around gadget" this would be a good starting point: https://en.wikipedia.org/wiki/Smallest-circle_problem

4D's first example could be found here: https://www.wikihow.com/Draw-a-Circle-G ... ree-Points

Onetrack
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Re: Circle around gadget?

Post by Onetrack »

Thanks both. A gadget to do this is what I'm after if possible!

https://www.wikihow.com/Draw-a-Circle-G ... ree-Points
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Adrian
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Re: Circle around gadget?

Post by Adrian »

Sounds like a project for Jim to me. :)

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Re: Circle around gadget?

Post by adze_cnc »

It looks as though that rather than "Circle Around" the gadget would be, specifically, "Circle Through 3 Points".

It could, though, be made generally as a "Circle Through n Points" gadget where n is greater than or equal to 2. Two points is a special case in that the diameter is the length of the line between the points and the circle centre is the mid-point of the line.

This potential gadget could work either of two ways:
  1. select existing vector (open or closed) then make a circle through the nodes keeping the original shape
  2. draw a shape within the gadget that is then converted into a circle through the nodes so that the circle is the only shape left

Onetrack
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Re: Circle around gadget?

Post by Onetrack »

Circle through 'n' nodes is certainly an interesting idea.

If you draw a triangle and the press R, the center point is not necessarily the same as the centre point for a circle that touches each of the triangle corners. This is what I am seeking. If a circle through 'n' nodes could fulfill that too that would be really great.
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Re: Circle around gadget?

Post by 4DThinker »

As far as I know there is no way to calculate/draft/draw a circle through 4 or more random nodes. When I played around in Aspire with the 3-point geometry I tried finding a way with 4 points. Although you can place 4 nodes on a circle, bump one off that circle and you won't be able to redraw a circle that includes them all again. Imagine 3 perimeter nodes with the 4th inside the area they define.
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Re: Circle around gadget?

Post by mtylerfl »

Onetrack wrote:
Sat Oct 16, 2021 5:30 pm
Circle through 'n' nodes is certainly an interesting idea.

If you draw a triangle and the press R, the center point is not necessarily the same as the centre point for a circle that touches each of the triangle corners. This is what I am seeking. If a circle through 'n' nodes could fulfill that too that would be really great.
Hi,

You can relocate/snap the triangle center point (or a star, or whatever shape) so that the new center point is suitable to center the item with a circle’s center point. I don’t know the correct terminology for the new center point location for triangles, stars, pentagrams…maybe it’s called the centroid???
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Onetrack
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Re: Circle around gadget?

Post by Onetrack »

But how do you easily find the centre of the circle? A gadget would do the heavy lifting.
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Re: Circle around gadget?

Post by mtylerfl »

Onetrack wrote:
Sat Oct 16, 2021 7:02 pm
But how do you easily find the centre of the circle? A gadget would do the heavy lifting.
Turn on Smart and Geometry Snapping.

Click twice on your triangle closed shape. You will see a “bullseye” where the current center point is located.

Click and drag the “bullseye” near where you think the “centroid” should be. The cursor will change to indicate when you are at that point. Let go of the mouse button and it snaps into place.

Now you can use the centering tools or manually drag either the circle or the triangle to snap/center to each other.

A video would be better, but my brief procedure description might suffice (I hope)
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adze_cnc
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Re: Circle around gadget?

Post by adze_cnc »

For n point greater than three they’d have to satisfy certain criteria:
  • all equidistant from a common point
  • be able to form a fully convex shape
Perhaps drawing any arbitrary points out. That’s the trouble with trying to visualize this sort of thing mentally you’re drawn to simple things such as regular polygons as part of solution.

Onetrack
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Re: Circle around gadget?

Post by Onetrack »

Michael, yes your technique helps find the centre. However how do you snap to the corner of the triangle? Seems the circle resize does not allow snap to work in this way. The square around gadget snaps perfectly and automatically around a triangle.
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Re: Circle around gadget?

Post by Adrian »

It's trivial to program a square around a triangle. A circle not so much.

By the way there was a feature added to VCarve a while ago that makes the Square Around gadget redundant for a lot of uses.

If you select the triangle and then hold down Shift while clicking the Rectangle tool you will get a rectangle drawn around the triangle. That also works with multiple shapes selected as well.

Onetrack
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Re: Circle around gadget?

Post by Onetrack »

Actually I think Michael's method works well. Snapping a circle from the new centre to the triangle points works! Thanks all for your input.
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