Spiral Stair
A spiral staircase defined by a center radius and a total sweep angle.
Spiral Stair is a helical staircase shaped by a center radius, a tread width and a total sweep angle.
Geometry
Outer radius = Radius + Step Width. Radius is the inner (center) radius and Step Width is how far each tread extends outward.
Sweep Angle is the total rotation of the staircase (1 – 360°) and Start Angle is where the first step begins. Direction comes from the Counter Clockwise checkbox, not the sign of Sweep Angle — a negative angle would flip the faces.
As with Stair, the step count is Height ÷ Step Height, capped at 256. The pivot sits at the bottom of the spiral axis.
Parameters
| Label | Script key | Default | Range | Description |
|---|---|---|---|---|
| Radius | r | 1 | 0.01 ~ 1000 | Inner (center) radius, in meters |
| Step Width | sw | 1 | 0.01 ~ 1000 | Radial width of each tread, in meters |
| Height | h | 2 | -1000 ~ 1000 | Total height in meters |
| Start Angle | ang | 0 | -360 ~ 360 | Angle where the first step begins, in degrees |
| Sweep Angle | sweep | 360 | 1 ~ 360 | Total rotation of the staircase, in degrees |
| Step Height | sh | 0.2 | 0.01 ~ 1000 | Height of one step, in meters — determines the step count |
| Counter Clockwise | ccw | off | on / off | When on, the stair climbs counter-clockwise |
sw (Step Width) and w (Width) are different parameters. Spiral Stair uses the dedicated sw rather than the shared w, to keep the tread width distinct from an overall object width.
How to create
-
Drag in empty space to set the center Radius.
-
Click to confirm, then move the mouse up to set the Height.
-
Click again to finish, then set Step Width, Sweep Angle and direction in the Inspector.
Scene view editing
The ±X and ±Z handles drive Radius and the ±Y handles drive Height. Step Width and the two angles are adjusted with the Inspector sliders and gauges.
Tips
For a stair between floors, set Height to the floor-to-floor distance, lock Step Height, then tune the path with Sweep Angle.
A half turn is Sweep Angle 180; for two full turns stack two 360° stairs — 360 is the maximum sweep.
If you need a central post, nest a Cylinder of the same Radius.
Script
In a script this shape is written as spiralstair.
spiralstair "Helix" r=0.4 sw=1 h=3 sweep=270 sh=0.18 @0,0,0
spiralstair "HelixCCW" r=0.4 sw=1 h=3 sweep=360 ccw=1 @4,0,0
See also — Shape Type List · Creating Shapes and Modes · Scene Script Syntax