Circle, Arc and Curve in SketchUp

SketchUp models geometry based on an edge. Edges make up any shape or surface. The next position on the basic SketchUp entities list is a circle. In this text, you can learn all the details that have something to do with arcs and circles.

In this article you can learn:

1. Circle sides in Sketchup
2. How to make a circle in Sketchup?
3. How to check the diameter and segment amount?
4. How to check circle circumference?
5. How to change circle segments in SketchUp?
6. Difference between circle and arc
7. What is curve geometry?
8. Create an arc between two edges
9. Round many edges corners at once

Why does SketchUp draw circles using a bunch of edges?

SketchUp uses Polygonal Modeling to approximate their surfaces. This means a set of edges describes every surface. The same situation is with circles, so each of them consists bunch of edges. The most practical information is that you need to decide.

Do you need smooth shapes with a big number of circle segments?
or
Do you prefer to set small circle sides to make the model easier to work with?

In other words, you can use a small circle sides parameter and get not natural curved shapes.

In that case, your model will be "light" and it will optimize performance. You can also set big values of segments to make the model realistic but work slower. It's your choice and you need to know about that decision to make at the beginning of the design process.

How to make a circle in Sketchup?

To create a circle in SketchUp:

1. Use proper tool from Drawing toolbar or press the "c" button (it is default circle shortcut key).
   
   
   
   
2. Check circle sides (segments). To change it use numeric keys.
   
   
   
   
3. Click the mouse button to choose circle middle point.
   
   
   
   
4. Set the circle radius with the mouse cursor or use numeric keys to set exact value.
   
   
   
   
5. Done!
   
   
   
   

How to check the diameter and segment amount?

Select the circle and open the context menu. With the right mouse button, you can open the Entity Info tray window.

You will find there the most important info about the circle. Radius and segments.

How to check the circle circumference?

If you need to find in the SketchUp circle circumference read this paragraph. This is possible only in newer SketchUp versions. If you work in SketchUp 2017 Make, you will not find this information. To get the circle circumference, open the Entity Info tray window. Next, select a circle that you would like to check.

For unexploded circles, the circumference remains constant, regardless of the segment settings.

But BE AWARE that if you explode a circle and select all those edges you will see a summary of edges length. Depending on the circle segments amount the length of all those edges will be different!

However BE AWARE that if you explode a circle and select all those edges you will see summary of edges length. It means that depending on the circle segments amount the length of all those edges will be different!

How to change circle segments in SketchUp?

There is an easy way to change the circle diameter and its sides (segments). Need to open the Entity Info window, as described above, and you can change the radius or segments as you need. When you change the numeric value in the window and press enter, the circle is redrawn with a new radius:

You can also set new segments for the circle eg. 6 sides:

Or change it to 360 with no time:

Difference between circle and arc

When there is a need to draw not full circle you can use Arc tool.

Basic functionalities work the same as circle drawing. But there is an extra parameter which is an arc angle and a start point. After you set the arc center point and its start point you need to show an arc angle as well. Same as before you can use also numeric keys to set precise values.

The difference between those two geometric entities is that a Circle is a full Arc with a 360° angle. When you open the Entity Info tray window you can see the proper entity type. The same as with the circle you can check and change basic parameters like radius and segment amount.

What is curve geometry?

Any circle or arc can be transformed into a group of edges. For example, if you select circle edge and open the context menu you find there Explode function. When you explode a circle shape every segment of the circle is a separate edge.

If you select a few edges that are connected to each other you can use the context menu: Weld function. As a result, you get a Curve. In other words, the curve geometry is a group of connected edges that are not a full circle or an arc.

Create an arc between two edges

If you need to create an arc between two edges you can use SketchUp native tools for that. Because you read this article you know all the needed information to draw a smooth arc on the corner of edges. But, there is a simple plugin that will help you a lot with that. Check this SketchUp round edges extension and read more about how to round edges in SketchUp.

To draw an arc between edges do a few simple steps:

1. select two edges
2. run plugin (launch setting window)
3. set radius and circle segmentation
4. done!

Round many edges corners at once

But what can we do if we have many corners to round?
There is a solution for that!

Use SketchUp round edges plugin.

It has a few advantages against the previous one:

1. you can set arc radius with slider or use precise value
2. there is an live view of the arcs - moving slider changes arcs online
3. you can select many corners to round at once