A sphere costs far more blocks than it looks
A diameter-eleven sphere is a hollow shell of a few hundred blocks but a solid one of several hundred more, and the gap only widens.
Most players estimate a sphere by its silhouette, then run out of material halfway through the second layer. The count is not the outline. It is every block whose centre falls inside the radius, and that volume grows with the cube of the diameter while the shell grows with the square.
Hollow versus solid
The generator's own counts for a sphere, shell against solid:
| Diameter | Shell | Solid |
|---|---|---|
| 11 | 314 | 739 |
| 15 | 582 | 1791 |
| 21 | 1166 | 4945 |
| 31 | 2522 | 15515 |
| 51 | 6810 | 69599 |
Double the diameter from 11 to 21 and the shell roughly quadruples while the solid goes up by a factor of about seven. If you are building a dome over a town square, you want the shell column. If you are filling a floating orb, you want the solid one, and you need a shulker box of shulkers, not a stack.
Layer blueprints beat guessing
A sphere is a stack of circles. The generator prints each layer as a width, so you place a row of that width, step inward, and repeat. Build bottom-up and the widest layer sits in the middle, not at the base — the classic mistake is starting at full diameter and discovering the equator is wider than your foundation.
For a roof, the same logic runs on a triangle rather than a circle. A gable roof is two staircases meeting at a ridge; the generator gives you the run and rise so the pitch stays constant instead of sagging near the eaves. A cone is a circle shrinking by one block per layer, which is why conical towers look wrong when the taper is uneven.
Arches, stairs and portals
An arch is a half-circle with the bottom row removed, so its block count is roughly half the matching sphere shell. Staircases are a straight run with a one-block rise per step, and the generator exports them as a diagonal you can paste rather than placing by eye.
Nether portal frames are the one shape here with a hard constraint: obsidian frame, interior at least two blocks wide and three tall, corners optional. A shape generator will not build the frame for you, but it will size the surrounding room so the portal is not jammed against a wall.
Java and Bedrock
WorldEdit's .schem format is a Java-edition schematic. Bedrock has no native WorldEdit, so Bedrock builders should use the layer blueprints and block counts by hand, or convert the schematic with a third-party tool. The generator's numbers are edition-independent — a block is a block.
Export and paste
The .schem export drops straight into your WorldEdit schematics folder. Load it with //schem load <name> and paste with //paste. Rotate before pasting, not after, or you will re-place every layer.
Plan the sphere, cone, arch or roof layer by layer and export it at the Build Shape Generators.