Image:St Basils Cathedral closeup
You'll notice that the model here is based on an octagon.
Each of the "petals" in the flattened out diagram is properly called a
'dart.' It you calculate the radius of each layer where the darts touch,
you can build small arcs with that radius and attach them to the flat,
turning the octagon into a circular dome. Then cover the ribs with
flexible strips. This is in fact how the wooden onion domes are formed,
if I recall correctly.
Sometimes the domes are then covered with something like shakes, at
The steps were:
1. Draw a profile of the dome. Try to make the segments of the arcs (I used three arcs) approximately uniform in size. I turned on endpoints with a value of two to see what I was doing.
2. Create the dome itself. I made this octagonal, which is what the one in the photo appears to be. Then I unsmoothed it.
3. Lay out a series of intervals on a vertical line corresponding to the lengths of the segments on the original profile. I used Xline.rb to turn a series of lines into guides to mark the intervals. Then copy the horizontal lines on one sector of the dome over to their corresponding positions on the vertical line.
4. Scale the horizontal lines by a factor of .5 to create a true half of the dome sector. Connect the dots.
5. Mirror the half to create a whole sector.
6. Copy the dome sector to a copy of the base of the dome and copy it around seven times. That's it.