How can I increase the accuracy of my torus's geometry?


Once I have built a torus / doughnut shape, is there an easy way to increase the accuracy of the underlying geometry?

i.e. When I go: View ==> Hidden geometry, I want to increase the number of segments in the circle. The reason why I want to do this is because I am going to want to use the shape for 3D printing and I am going to need things to be pretty accurate when I add/remove stuff.

Or should I build the torus from scratch but using a circle that has a greater number of steps (or whatever the word is - “segments” ?)

Many thanks

You will need to redraw using a circle with more sides. After activating the circle command, just type the number of sides you want.

OK I feared as much. Thanks :smile:

Notice that the shape is the product of two circles: the profile and the path. Each contributes to the granularity of the final shape; to ensure a mesh that is uniform in both directions, change the number of segments for both circles.


Too true! Both “circles” should be redrawn to make the smoothest possible geometry.

Also, @ship69, you may want to try Artisan to smooth out the existing geometry, before startign from scratch.

Wait - except that I can’t make it work.
Here’s what I did:

  1. click on the circle tool
  2. type in a number (e.g. “100” using the keyboard)
  3. click where I want the circle to start, and start dragging
  4. type in the number I want (e.e.g “25.5”)
    ==> but it drew in 24 sides

Hang on, it worked for 48 sides. What are the constraints/best practice for this?

hit the Enter key after typing 100

stick to multiples of 4 drawn on axis, is best practice…

1 Like

Step 2 sets number of sides–hit Enterto execute, then set your center.


Why didn’t I think of that [sigh!]
Yes, enter works.

Would 2 to the power of something be even better? e.g. 128.
Either way would 128 be a reasonable number for a smallish slightly complex 3D shape that will have lots of curves?

PS What is the convention here - does it matter who’s answer I tick? Does it matter if I ask more than one question in a thread or would it be better to ask them in separate threads?

You want to have a point on axis at each cardinal point. Hence 4 on axis.


So would 124 be just as good as 128 - as both are multiples of 4.

there are a couple of plugins that calculate the max number of side that a 3d printer will see, any more are just slowing things down…

also, draw at scale then scale back down to avoid the tiny edges that can happen when maxing out the geometry…

what is the finished radius for each circle?


You may wish to peruse this previous discussion:


I have a number of radiuses (‘radii’) that are 4.5mm

I dont know if it helps but I opened the “3D Printing - Millimeters” template.

Are you saying I should draw at 10x larger scale and then shrink everything to one tenth when finished. (Please tell me x8 is better because that would be a serious pain converting all my dimensions)

From Gully’s link it looks like 32 sides would be a reasonable place to start.

You can try any factor you like. The need is to get the geometry larger than SketchUp’s built-in tolerance of about 0.001 inch. In metric, powers of 10 tend to be easy to work with. In Imperial units, almost any scale factor is a pain! Quick, what is 5 3/16 inches when scaled up by 20?

Aside: I have no idea how the Americans managed to build the Space shuttle in yards, feet and inches. :wink:
Metric is much simpler.

to be be honest, don’t use the 3d printing template…

it’s a massive file with little of any use in it…

I use a metre template and hide the dims, then you type 25.5 etc… and imagine it’s mm…

when finished use the tape tool on any edge and add mm to the measurement box and it scales the lot…


In all likelihood, they worked in metric! It is largely the American public that stubbornly clings to Imperial units.