Volume of a cylinder

cylinder.skp (125.3 KB) I made a simple cylinder. Entity info confirms it is a solid, but fails to show its volume. What’s up?

It shows a volume for me. Maybe you could share a screen shot of what you are seeing? Are you expecting to see the volume when the group is open for editing?

It is a group within a component, double click the component and you will see the volume.

Good point. When opened as it was uploaded, it’s just a group. No component.

You mean it is not the same as π x radius² x height?

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I don’t follow how you did that.
I had not made it a component, only a group.
What did you do to get the volume to display?

Ah, no, because this is not a true cylinder.


Thou might know, and I, but not all of us!

Please explain why it is not a true cylinder, and how I can make it so.

For practical purposes it is a cylinder but in reality it’s not because the circle isn’t really a circle in SketchUp.

So how did Solo get SU to display its volume?
How can I get it to?

I don’t see that he shows a volume in his post.

DaveR, sorry, it was in your post that I saw the volume displayed.
BTW, I’m using SU 2017. Is that the problem?

It shouldn’t be. If you select the group, it should show you volume. You do need to expand the Entity Info window by clicking on the little button below the X in the top right corner, though.

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DaveR, thank you! At last I got the answer!

To reiterate, show us so we might be able to see what the problem may be on your end.

It is not a true cylinder because everything in SketchUp is represented using straight edge segments and planar faces. SketchUp fakes curved surfaces by making them from a collection of flat faces, hiding the edges between the faces (softening) and doing a blended shading across the edge so that the two faces seem to form a smooth curve (smoothing). If you make something such as a cylinder 1 unit radius and 1 unit tall and show its volume (now that you’ve seen how), you will find that the volume is less than the true geometric calculation. It is missing all the little arced parts between the flat faces and the ideal curve. If you increase the number of sides in the circle (actually a polygon) before you create the cylinder, you can come closer to the theoretical value. At 96 sides it is close enough for most purposes (about 0.06% error).

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That would suffice… Even Pi is an approximate number, is it not? (in computers)

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