Building segmental arches in Minecraft

A segmental arch is a slice of a large circle: shallower than a semicircle, and it meets the piers at an angle instead of vertically. That is how stone bridges cross a river and gates span a wide passage without growing tall. VoxShaper works out the circle from span and rise and shows you every block.

Setting the shape

Radius Z sets half the clear width, the rise sets how far the crown sits above the springing line. The smaller the rise, the shallower the arch. Once it reaches half the span it is a round arch, and above that it turns into a horseshoe arch. The pier height sets the vertical part below the springing line, the arch thickness how thick the arch is.

With the bridge fill the space above the arch is filled up to the crown, which gives a bridge with a level deck. A larger radius X turns the arch into a shallow vault.

The arch types

Round/pointed is a semicircle squashed or stretched to the rise. It always leaves the piers vertically, and the pointed arch slider gives it a point at the top.

Segmental and horseshoe are the same arch: a true circle through both springing points and the crown. The rise moves the crown, and the circle follows. If it is smaller than radius Z, the centre of the circle lies below the springing line and you only see a shallow cap. That is the segmental arch. If it is larger, the centre lies above the springing line: the arch grows wider than the opening and narrows again towards the bottom. That is the horseshoe arch.

The transition is seamless. With the rise equal to radius Z it is exactly a semicircle. Drag the rise across that limit and the selection therefore switches between segmental and horseshoe by itself.

Build or export

Rebuild the arch layer by layer or download it as a schematic for Litematica, WorldEdit or the Structure Block.