Minecraft Circle Generator

Building a circle that reads as round

A grid can be mathematically correct and still look wrong once it is 30 blocks tall. These are the things that decide which.

1. 1

   Odd diameters have a centre block, even ones do not

   An odd circle has a single block at the middle, so it is the one to pick when something has to sit dead centre — a beacon, a pillar, a nether portal. Even diameters put the centre on the corner between four blocks, which is fine for a wall and awkward for anything you want to align to.

2. 2

   Build the outline first, then fill

   Lay the ring one row at a time using the per-row counts, and only fill it in once the whole boundary closes. Filling as you go means a miscount two rows back becomes a bulge you have to tear out.

3. 3

   Quarter it and mirror

   A circle is symmetrical on both axes, so you only have to count one quarter. Place the four axis blocks first, build one quadrant, then mirror it three times — four times less counting and the errors cannot drift.

4. 4

   Small circles always look blocky

   Under about nine blocks there are not enough blocks for a curve to exist, so a 5 or 7 reads as an octagon no matter how it is generated. If a tower needs to look round, go wider rather than fighting the grid.

5. 5

   Stack it for domes and spheres

   A dome is a stack of circles whose diameters shrink toward the top. Generate each layer separately and note the diameter for each height rather than eyeballing the taper — the shape is only as good as the widest wrong layer.