What causes circles in solids to (sometimes) change to connected line segments?

Many times, circles that are part of a hole through a solid become “unselectable”. When you click on the circle, only one segment highlights.

So, you can’t use “entity info” to change their radius. You also can’t use the “Guide Tools” plug-in to find the center of the circle. I find the center by drawing perpendicular lines to a couple of the circles straight line segments, but sometimes getting the purple perpendicular inference is a hassle.

The circles always seem to “stay circles”, until I combine solids using Union under Solid Tools. But, sometimes they stay selectable, even after the solid with the hole is “unioned” with another solid.

I though maybe if had something to do with the number of line segments in the circle, but I have experimented with that and have not seen a consistent correlation.

My work-around is to simply leave the solids separate, or at least don’t combine them until I think I’m sure I won’t have to mess with the hole sizes or reference the hole centers (but I’m often wrong and DO have to mess with them again).

I’m wondering what causes the circles to be no longer selectable as a circle, and is there an easy way to prevent this from happening?

I don’t know of a comprehensive list, but some edit operations cause SketchUp to lose the metadata that identifies a sequence of edges as a circle or circular arc. The only way to restore the info is to redraw the circle. There are extensions that facilitate this. I don’t think there is any way to prevent it in the first place.

1 Like

Can you name one of the extensions that will facilitate redrawing the circle?

Curvizard by Fredo from sketchucation.


I’ll check it out tomorrow morning.


There’s also nobob’s Exploded Lines to Arc from the SketchUcation Plug-in Store.

1 Like


This one.
I previously always recommended it, until fredo’s Curvizard had the option and much more besides

1 Like

Thanks for the correction, Box. I use one by ni called Lines to Arc but can’t find any more in EW or the Plug-in Store.

I should give Curvizard a go myself.

1 Like

Actually called Exploded Arc lines to Arcs by Nobnob, ni is the tool itself in the menu.
That is the one I posted the link to, I don’t believe it was ever in the E Warehouse.

1 Like

I’ll try them all, once I get my next 18 hour 3d print started. But, I tried nobob Lines to Arc from the SketchuCation Plug in store, and it worked great!

I used it to convert two adjacent segments to an arc, then the Guide Tools extension to put a guide point at the center of the arc. With the center accurately located, I draw the circle I want, then delete the segments that comprised the original circle.

This will be a time saver since many times I don’t need to change the circle radius, but just need the guide in the center of it. Maybe one of the other extensions suggested automate more of the task, like not only creating an arc from the selected segments, but also deleting any other segments on the circle defined by that arc, and finally actually drawing the new circle?

But, I will try them out myself later today


For what it’s worth, SketchUp has a native feature to place a guide point at the center of an arc or circle. Right-click on the arc or circle and choose Find Center from the pop-up context menu.

1 Like

If you select all the segments of the circle and use either tool it will become a full circle again with center inference available. (assuming all segments are originally from a circle, therefore all are the same length.)

And if all you want is the centre or implied centre from two or more line segments that lie on an arc, there’s a tool by @ChrisFullmer in the EW called Arc Centerpoint Finder (Search | SketchUp Extension Warehouse). Select any two lines from the exploded arc, then run the extension from the Extensions/Chris Fullmer Tools submenu to place a guide point at the centre.

Thanks for that!

Yes, but it’s often difficult to select all the segments without selecting more than I want. For example, the solids with the holes typically have geometry directly on the other side of a solid surface–typically a different size hole(s).

I’ll have to use the extension for a while to see what happens when unwanted segments are included in the selection.

Still, it’s going to be a big help

If that happens, the Lines to Arc extension usually won’t do anything, and tell you why.

Haven’t yet tried the Curvizard equivalent.

Curvizard seems better to me. You can click on a surface bounded by arc segments, then another click (on the green check mark) to get the circle. So, you don’t have to futz around to get all the segments or delete segments if you create a circle from a subset of the arc segments

Then, as TDahl said, you can right click to get a context menu at the center of the circle.

jon_mccelnahan, haven’t tried “Arc Centerpoint finder” yet but it sounds like an extra step or two compared to curvizard.

So much help here–wish I could award “Solution” to all of you! Not really an answer to the question (how to prevent loss of the circle metadata in the first place), but nice extensions to recover it.

I think Box was the first to mention Curvizard, so I’ll call that the “Solution”.


Useful to know. I must try Curvizard.

That’s too bad.