Arch

The basic arch shape is a curved symmetrical shape (see A in the image below). You can customize the basic arch shape to create tunnels, pipes, roofs, and many other objects.

Basic arch shape (default values)

Tunnel: Arch with increased depth and thickness

Wheel: Arch with increased number of sides, thickness and degrees (and no end cap)

Roof: Arch with 2 sides and increased depth

When you customize an arch shape, keep in mind that when you change the thickness and number of sides, it is relative to the Radius and Arch Degrees values. For example, two arches with the same thickness (15) but where one arch has twice the radius as the other (3 vs. 6), look very different. The one with the smaller radius appears much smoother than the other.

You can customize the shape of an arch with these shape properties:

Property:	Description:
Radius	Set the radius (size) of the arch in meters. A change in radius affects the overall height. The default value is 3.
Thickness	Set the thickness of the arch in meters. As this value approaches the Radius value, the smaller the doorway becomes. The default value is 0.5.
Depth	Set the depth for the arch in meters. The higher the value, the longer the tunnel effect. The default value is 1.
Number of Sides	Set the number of sides for the arch. The more sides you use (relative to the size of the Radius), the smoother the arch becomes, so the closer you get to a semi-circle. Conversely, if you this value to 2, the arch turns into a peaked roof, regardless of the radius. The efault value is 6.
Arch Degrees	Set the circumference of the arch in degrees. For example, an arch of 360 degrees is circular. The default value is 180.
End Caps	Enable this option to create faces for the ends of the arch (default). Disable this option if you know the ends are not visible to the camera (this is an optimization strategy that reduces the number of polygons that Unity has to render).