In most cases I have a preference for my circles to look like actual circles and not angular segments. So I may use more segments to achieve this. Is there a way to keep circles, once placed from segmenting into pieces? Is there a segment number that is ridiculous to use. I sometimes use 250, 300, 500 or 750.

It is generally regarded as good practice to use a number of segments in a full circle which is a multiple of 4, 6, 8, 12 or 16, and to draw them starting with a radius on one of the axes.

That way, all the ‘cardinal points’ are on axis too, and subdivisions which are 1/4, 1/6, 1/8 etc of a full circle all have a whole number of segments, all of the same size.

I have rarely found it necessary to use more than 96 segments in a full circle, but occasionally might go up to 360 if I want to draw a 360 degree protractor with 1 degree radial markings.

I would not use 100, 250, 300 or 500 segments, but rather 96, 240, 360 or in extreme cases 720.

Circles or arcs will remain as entities unless:

you draw an intersecting line or arc

use a circle or arc as a path for FollowMe.

And if they do get broken up into separate edges, you can at least weld them back into a curve, or recreate an arc or circle using a plug-in in desktop versions of Sketchup - for example Lines to Arc.

There isn’t a fixed number of sides for circles and it depends on how large they appear in the model. The more sides you use the more likely you are to have problems. I rarely use more than 96 sides and in most cases it seems best to use a multiple of 12. Don’t use any more than you absolutely hve to.

Along the lines of what others have said, I use 24, 36, or 72 segments so that I have vertices that I can draw to at 15deg, 10deg or 5deg, arc lengths around the circumference of the circle – which is sometimes relevant because the length of the radius of the circle is only accurate when measured to a vertex – which is sometimes relevant when you chop the circle up into pieces.

When optimizing for performance, I’ll use 12 segments when drawing circles that are going to be used to model small/thin, extruded elements (using Push-Pull or Follow Me), like pipes, wires, table legs/casters etc. especially when the lack of detail will go unnoticed.

I agree with John: 4 sides or multiples. One side for each quadrant. Most my cilindres are 4 sides mostly on rails. They don’t fail at elevations and they are as simple as you can get, when multiplied by hundreds in the same model.