# Catenary

Curve

Catenary >

<Options>

The Catenary command draws a curve that a hanging chain or cable assumes under its own weight when supported only at its ends.

#### Note

• Catenary curves cannot be exactly represented using NURBS, so the output is always approximate.
• The created curve endpoints are exactly at the picked points, and the curve end tangents are evaluated from the actual catenary.

#### Steps

1. Pick a location for the start of catenary
2. Pick a location for the end of catenary.
3. Pick a location to show the catenary axis direction.
An arrow points toward the default direction.
Press Enter to accept the default.
Or select a point depending on the options.
4. Pick a point on the catenary.
Command-line options

Mode

Specifies the drawing mode for the catenary.

##### ThroughPoint

The next pick specifies a point for the catenary to go through.

#### Note

• If the two end points are on the same line perpendicular to catenary axis, the catenary apex cannot be at either end point, it must be between them.
• If the axis is not perpendicular to the line between the two end points, a catenary with an apex at the end point does exist. Press Enter or snap to the second end point to make the apex at the second point.

Curve endpoint (1) and catenary apex (2) are at the same location.

##### Point on catenary

Pick a location that will be on the curve.

##### Length

Type or pick the catenary length.

The length needs to be longer than the distance from catenary start to end.

##### Parameter

Type or pick the catenary parameter.

#### Note

• The basic catenary equation is y=a*cosh(x/a).
• The catenary parameter is "a" in the equation. Smaller numbers make longer, saggier curve, larger numbers make shorter, tighter curve.
• The command remembers the length and parameter in all four modes.
##### Apex

The last pick defines the catenary apex height.

Output

Specifies the output type.

##### Smooth

Creates a smooth curve

##### Polyline

Creates a polyline.

PointCount

Specifies the number of control points in the output curve. The more points, the more accurate the catenary approximation.

MarkApex

Places a point object at the catenary apex.

The point is evaluated at the actual catenary apex, so it may be slightly off the output curve, especially if the output is a polyline.