Arcs not filling

Hi all, I’m new to the SketchUp forums. I have a question about filling arcs…

When using the Arc tool to draw quarter and semi-circles on a plane, then drawing the same arc above and connecting the two ends with straight lines, the arc is not filling and I have no way of getting it to fill.

I’m using the free web version, is this some kind of Pro version feature or something?

Thanks in advance.

If your arcs are truly coplanar and all the edges are closed it should generate a face. Download your model to your desktop and upload it here on the forum by dragging the file into a reply window. If we can see the model we can likely tell you what is going wrong.

Edit: having just re red your post, it sounds a bit like you are expecting the vertical rounded faces between your above and below arc to form. This will not happen. Make a complete face of your bottom arc then push pull it upwards to form vertical faces between arcs.

Hi, thanks for your quick reply!

Yes, I think you have the idea of what I’m trying to achieve but how do I push/pull a line? I do not want the face of the arc to have thickness. I’ve downloaded models from the 3D Warehouse which have this single line thickness arcs on two and three planes. A good example is the rear wheel-arch of the Mercedes Sprinter vans in the Warehouse.

I’ll see if I can upload the model here.


You must push pull as a face. Erase the back when you’re done if you like.

You don’t. Create a face by drawing a line between the endpoints of the arc and then extrude the face. Erase the lines to leave just the curved surfaces.

So how would I create a 3D fill then?

I’d use Follow Me for that instead of Push/Pull.

You would model faces across the plane of the back side. Let’s make sure we are talking about the same thing: SketchUp is a surface modeler, there is no fill, nothing is solid. Everything is a collection of planes. An object can have outer bounds but it is still “hollow” inside.

@DaveR Can you clarify how “Follow Me” would achieve this please?

@endlessfix Can you clarify how as a “surface modeller”, SketchUp could produce a solid face fill as per the example I’ve provided?


I drew the shape shown in green in my first screen shot. I also drew a path consisting of a couple of line segments and an arc. I selected the path, then go the Follow Me tool and then clicked on the green face.

Click on the magnifying glass at the top of the toolbar on the left side and search for Follow Me to get more information about using that tool.

All geometry in SketchUp is made up of zero thickness surfaces. To “fill” something you model surfaces around the area you want to enclose.

It’s a little difficult to tell what is going on in your “example” image. It looks a bit like the shape I’ve made and closed here.

Okay. Closing that model is simple and I know how to do that. What I’m trying to achieve is the smooth curved section. If I use a series of arcs then the resulting curve is not a curve but a series of flat panels resulting in a surface which is not smooth but ends up looking like a radar dome or something similar.

SketchUp only works with flat surfaces. You can increase the number of segments that make up the curves which results in smaller faces which tends to create a smoother appearance but you’ll never eliminate the facets altogether. Keep in mind that SketchUp doesn’t like very short edges (less than about .01 in. so if your model is small you will need to do something to be able to create very tiny faces. Working at a larger scale is one way, The Dave Method is another. Box did a nice tutorial on that method which you can find in the search.

Here’s an example from a recent model I did. This is certainly overkill for most applications.

Nice apparently smooth surfaces.

Hidden geometry displayed. There’s nearly 100k edges in this model.

The collar and screw make a file that is over 11.5 Mb. Not so bad on it’s own but way too much detail to use in a larger model. FWIW, this was done because someone elsewhere made a statement SketchUp can’t be used for detailed models. This is a locking collar to go on 1/4 in. diameter Acme-threaded lead screw.

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Wow! Okay, that’s certainly food for thought, I guess I’ll just have to get edging…

Thanks for your insight, quick responses and help Dave, it’s much appreciated.

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