How to add circles inside another circle

Question

I want to create an object which is similar to but is not a rainbow ie ever reducing circles inside the main circle (or vice versus starting with a small circle or cylinder.) See image below of the object I want to create.

I tried using a circle and also a cylinder which when complete I would 'cut' in half using boolean.

I tried selecting all the edges (Alt + click on an edge) and then use extrude and also scale which I could not get to work the way I wanted.

What is the method please.

Image of my building with the half circle now included.

Answer 1

1. Add a mesh circle with Shift+A > Add > Mesh > Circle, open the tool options in the bottom left of the viewport and set Fill Type to N-Gon. Select the number of vertices according to what you need or how smooth you want the circle to be and the radius to the desired size.

   

2. Press Tab to go into Edit Mode, A to select all if it's not already selected, then I to inset the circle face. Drag the mouse until the inner circle has the size of the smallest circle you want to have. You can also do this with measurements. Let's say the outer circle has a radius of 1 m, the inner should be 0.2 m, then enter (1 - 0.2) = 0.8 while insetting.

   

3. After insetting, press Ctrl+R for the Loop Cut tool. Move your mouse over one of the "spokes" until a yellow circle appears. Scroll the mouse wheel up/down to change the number of cuts according to how many circles you want. Left-click to confirm the number, then right-click to let them stay in place and have even spacing between them (unless you want them to move inwards or outwards).

   

4. Press Numpad 7 to go into top view. Select the two inmost opposite vertices at the horizontal center and press J to split the center face.

   

5. Now select all vertices below the central line. Hit X > Delete > Vertices to remove the bottom half of the circles.

   

6. Select all with A, then press E to extrude the faces upwards.

   

If you now want to get rid of the "spoke" edges to have the (half) rings as single n-gons, you can do the following:

1. In Face Select mode hold Alt + left-click on the edge between two faces of a ring to select the complete loop.

   

2. If you hold Shift+Alt while clicking you can even select more rings. Just keep a space between them to ensure you don't get just one big face instead of rings.

   

3. Now hold Shift to not lose the current selection and left-click on the selected faces on the front to deselect them. You could also use Shift+Alt and left-clicking twice on a vertical front edge to select and deselect the loop around the shape. You now have (half) rings on the top and bottom of the mesh selected.

   

4. Press F to make each separate selection a single face.

   

   You can now repeat this process with the rings that are still multiple faces. End result:

   

Answer 2

A variation on Gordon's method.

1. ShiftA add a circle
2. X delete lower faces
3. CtrlShiftB bevel center vertex with 1 segment
4. CtrlR cut edge loops into radial quads.

Answer 3

Another way of creating a circle subdivided this way is geonodes:

It's a 0 height cone, so in order to not have overlapping geometry, remember to set the Fill to None. Once you're happy with the settings you can apply the geonodes modifier.

Beginner guide

Using Geonodes is hard, but entry point is very easy, just open the 2nd last workspace:

And in the center of the screen click the "New" button:

It will automatically add the Geometry Nodes modifier to the active object, as well as create a new geonodes tree with two nodes:

In order to apply the changes as seen on the first image, just delete the "Group Input" node, then either ⬆ ShiftA, S or drag a link from "Group Output" and search for "Cone":