Games : How can I build a smooth dome?

I'd like to build a dome roof on a building. There is a trick using command blocks and blocks "riding" minecarts to create a smooth sphere:

It'd like to use something like this to create a half-sphere for my roof.

The trick via command blocks and minecarts works but takes a lot of time. Is the only option to use command blocks, or is there a mod or filter to do something like this or to automate the minecart trick?

---

To be clear, it should be like this:

It should not be like this: