Arch

An arch extruded from a rectangular-section arc.

Arch extrudes a rectangular-section arc through a depth — doorways, bridge spans, window frames.

Geometry

An arc of outer radius Radius 1 and inner radius Radius 2 is drawn on an upright plane and extruded by Depth. The arc opens symmetrically about vertical by Angle, and at the default 180° its feet reach the ground (y=0). Both ends are closed with flat caps.

Opening width = Radius 2 × 2
Overall width = Radius 1 × 2
Arch thickness = Radius 1 − Radius 2

Rotation turns the shape itself around Y to change which way the arch faces.

Parameters

Label	Script key	Default	Range	Description
Radius 1	`r1`	1	0.01 ~ 1000	Outer radius in meters
Radius 2	`r2`	0.75	0.01 ~ 1000	Inner radius in meters — must stay below the outer radius
Depth	`d`	1	0.01 ~ 1000	Extrusion depth in meters
Angle	`ang`	180	1 ~ 360	Arc opening angle in degrees
Rotation	`rotation`	0	0 ~ 360	Y-axis rotation of the shape itself, in degrees
Sides	`sides`	12	2 ~ 128	Divisions along the arc

Angle at 360 closes the ring. Below 90 it becomes a partial arc, useful as a corner bracket.

How to create

Drag in empty space to set the base rectangle. The long side becomes the arch span and the short side the Depth, and the transform auto-rotates to follow the long side.
Click to confirm, then move the mouse up to set the arch height (= outer radius).
Click again, then move the mouse to set the inner radius (the arch thickness).
Click once more to finish.

Scene view editing

The ±X and ±Z handles drive Radius 1 and Depth, and the ±Y handles drive the arch height. Inner radius and angle are Inspector-only.

Tips

Arch has the longest draw sequence of any shape — four stages. It is usually faster to rough it out and finish in the Inspector.

To cut an arched doorway, use the Arch as the cutting solid for a Boolean, or place it in front of a Room wall as a frame.

Script

In a script this shape is written as arch.

arch "Doorway" r1=1.2 r2=1 d=0.4 ang=180 sides=24 @0,0,0