"Closing" 3 connected arcs

I’m a SketchUp Make newbie, so please forgive me if the answer to my query is obvious! Just having a play around and I have created 3 arcs on 3 different planes, connected as per the attached image. I want to “close” the model by creating a face formed of the 3 curved lines (forming what it looks like would be 1/8 of a sphere), but I can’t see how to do this. Can someone help?



You could try making a sphere and then remove 7/8. Just a hint.


Thanks, Shep.

You know, I thought this might be a solution, but isn’t that a bit long-winded? Isn’t there a way of just adding a 3-sided face to the open side of the model, using the curved lines as edges?

It ought to be as simple as using the FollowMe tool. Select the edge in the X-Y (red-green) plane, then choose the FollowMe tool and pick one of the vertical faces.

However, because end of the arc isn’t at right angles to the axis, the shape goes beyond the axis.

So, instead, first draw a full circle on the X-Y plane, then rotate it half a segment to get the middle of a segment on the axes. Then draw lines from the origin to where the axes cross the circle, and delete the three-quarter circle you don’t want. Rotate/copy the pie to the X-Z (red blue) plane. Delete the X-Y face and origin to Y line from the first quarter circle, then use FollowMe on the arc, by first selecting the arc, then choosing FollowMe tool, then click on upright face. Reverse faces at the end, to get the front faces outside.

Like this:

Thanks, John.

I tried a version of what you said… firstly by selecting and deleting one of the faces and its horizontal edge. Then selecting the bottom curved edge, choosing Follow Me and clicking on the upright face, which seemed fine at first… until I rotated it round a bit:

And realised the angles weren’t right!

(I’ve combined 3 images, as being a new user, I can only insert 1 image per post, so hope the above makes sense)

Then I remembered what you said about the arcs not being at right angles to the axes… which I don’t understand! I mean, why wouldn’t they be, if I have followed the coloured axes? Are these not at right angles? If not, why not? Anyway, I think I’ll now have a got at doing it how you said…

Well I don’t exactly know why it worked, but it did…

Thanks again, John, for your help! :+1:


The situation John referred to results from two aspects of how SketchUp draws circles and arcs: 1) it actually represents them as polygons, that is a sequence of straight edges with vertices on the actual circle, and 2) SketchUp places the first vertex wherever you click the first point (after selecting the center). Since the second vertex is also on the mathematical circle, it isn’t on a line perpendicular to the axis.

My geometry’s feeling rusty… trying to understand this…


See the sequence of operations in this example:
Eighth Sphere.skp (138.2 KB)