Still not getting cardinal points

I have asked something like this before and have been given some great info… But every time I want to use it I still can’t make it work.

I am talking “cardinal points” on cylinders to change the size.

I just created this


and want to make the inside a bit bigger whilst maintaining the wall thickness…

If I move the mouse around the ouside I find the cardinal point


And now I can easily make it bigger/smaller by moving this line

But I can’t for the life of me find the same point on the INSIDE… I run my Move tool around the inside and I just never see the Cardinal line appear…

I struggle with this all the time and just wonder if I should learn another way to achieve the same.

How would I take this object and move the outwall 5mm and the inner wall 5mm, so that the openeing increased from 40 to 50mm and the wall stayed teh same (2mm)

I could us scale… but that would alter the wall thickness and for a model this simple I could just draw it again quicker than I could write this… But I need to learn how to handle this as I run in to this all the time.

I am greatful for any help you can offer.

I have attached the file should anyone want to take a look.

Untitled.skp (1.2 MB)

How was the inside made? Was it drawn as a separate circle before the shape was push pulled or was it created by Push/Pulling the outside circle?

As @TheOnlyAaron asked, how did you draw that? The inner edge at the top is not a circle, it is just a bunch of separate edges and that’s why the Cardinal edges thing doesn’t work. Here I’ve remodeled it so that edge is a circle and the Cardinal Edges thing works fine.

Odd… This is another part of SU that I never get… How circles become a bunch of edges

I made this by

  1. Draw 22.5mm circle (48 segments)
  2. Pull up 2mm
  3. Draw 20mm circle
  4. Pull up the 2.5mm outer ring to 40mm

And this got me to this, where the inner circle is a circle

But then I used Fredos Round Corner to create the bevel… And now as you say its no longer a circle

So “round corner” breaks the circle… And thats why I see this a lot as I use RoundCorner for this kind of thing…

I could have just moved the inner ring down to create the same…

I get it now… So Roundcorner make not be helping me here… Is there a way to “fix” this once its happened? (i.e make a collection of edges back to a circle so the cardinal move/resize works again)?

Round Corner is not helping in this case because it creates exploded curves. And yes, for something as simple as this, using the Move tool makes more sense and it’s actually faster.

Cheers… Clealy the reason I see this often is that I am too dependant on RoundCorner and us it too often.

I will bear that in mind… Cheers.

I just tried a little experment and hoped it would work, but it didn’t…

I started with this

I then used roundcorner to make this:

Then I selected the edges of the circle and used TigWeld to make them circles again:


But now there is no Cardinal Line again, even though the top and bottom of the cylinder is a circle.

I even deleted the bevel at the top to make this a cylinder again, but no cardinal line

Is this just something unavoidable and a side effect of a circle getting exploded? Does it mean that even if you rejoin it, you can’t get Cardinal functionality back?

Yes. Cardinal Points and Cardinal Edges only work with intact circles and polygons.

So last question… is there any way to convert edges back to a circle if they get exploded.

I thought that using TigWed I was able to do it… Like this


But I guess this is still not a circle as it doesn’t act the same way as a true circle does (where as it shows you the radius and centre point)


So by TigWelding the circle back, all I have is a connected ring of edges rather than a circle… Is there a way to get the ‘circle’ back?

Weld, TIG-Weld, etc. won’t convert a bunch of edge segments back to a circle. They will only weld them together. There’s a plugin from “Nobnob” in the Sketchucation Plugin Store called Lines to Arc that will do it, though. Once it is installed you’ll find it in Extensions>Ni>.

You should be paying attention to Entity Info as you are selecting entities in your model. It’ll tell you what you are selecting. If you aren’t already doing so, I would suggest keeping Entity Info active at all time.

By the way, are you using Sketchup 2018 or SketchUp 2017 Make? There is no 2018 Make.

Doh… I had that already…

Just used it and its now a circle again


But interestingly I now have a cylinder with 2 “circles” top and bottom but no cardinal lines… So I still havn’t fully understood a way to get this back to normal after breaking it.

As for my version I will correct that now…

Edit: Ignore that… The cardinal line has just appeared… Sure why it didn’t a minute ago, but its there now


So after exploding the circle (using Roundcorner) and then remaking it again with Line to Arc, its all back to normal.

All understood now… Cheers

In your first screen shot the cursor was on the edge of the circle and specifically on the Cardinal POINT, not on the side of the cylinder where the Cadrinal EDGE is located.

That was just a bad choose of screen grab… I was moving the mouse all over the side and couldn’t get the Cardinal Edge to appear…But after switching back to my browser and then back to SU, it started working.

So I guess I was just doing something wrong.

Edit: Just went back a few steps are recreated what I did and it worked fine… I must have had something selected when I tried to find the Cardinal Edge… So ignore all this.

By way of belated background, the fact that a bunch of edges constitute a circle is held in metadata attached to them. The metadata includes the center, normal vector, plane, radius, x axis, y axis, start angle, end angle. It is this info that lets SketchUp do circle-specific things such as the cardinal points and edges.

Unfortunately, some kinds of editing make it impossible (or at least unsafe) for SketchUp to continue to treat the edges as a circle, so SketchUp discards the metadata. Further, neither the GUI nor the Ruby API provide any direct way to restore it. Welding the edges back into a curve does not regenerate the metadata. Extensions such as you found actually work by creating a new circle that overlays where the old one was. They perform geometric analysis to recover the original circle parameters.

With SketchUp 2018, a “damaged” circle can usually be re-constituted to full health by drawing an identical circle on top of the existing edges. I have used that feature many times, for which I thank the SketchUp team.

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The Extension Lines to Arc from SketchUcation, that DaveR mentioned above, or redrawing the circle, as TDahl indicates, are the only ways I know to convert either loose or welded edges back into a circle or arc. And Lines to Arc won’t work unless the edges all remain of identical length.

That’s what comes to mind…(not closely related to the topic)
Just for fun, you can create a circle with unequal segment length:

But it is a good question… does it make sense? :blush:


I’ve been using and recommending nobnob’s plugin for a long time but at some stage in the recent past Fredo quietly added repair of arcs and circles to his Curvizard. It will fix multiple edges in one hit. Same rule applies, it can’t fix something with different segments.

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What was most helpful about your post is the fact that you show when you know you are selecting a cardinal point

When you were resizing the top inner circle, you spent time trying to hit the exact point, and panned/zoomed until you got it… I couldn’t work out how you knew you had the Cardinal point…

So then i went to SU and had a look and realised that when you are are NOT selecting the Cardinal point, the entire circle goes blue… But when you are over the cardinal point, it doesn’t highlight and stays black.

I assume thats what you were looking for in your video? Or are there any other tells?

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The cardinals are found at the four points of the compass, hence the name. So if you always create your circles on axis, in other words pull the circle out along one of the axes rather than just randomly, you will find then at those four points or other appropriate divisions. And yes, the selection disappears when you hit the point.