Minecraft wiki entry for Curved_roofs, associated text: A segmented dome can be created by taking just the top rows of a larger-than needed dome. The effect is to produce a dome that joins the building walls at a shallower angle, whereas a hemispherical dome would be fully vertical at the point it joins the walls. In this image, the top three layers (diameters 14, 12 and 6) of a diameter-22 dome were chosen.