Arc From Element

Used to construct an arc based on a selected base element that controls tangency at one end.

You can access this tool from the following:

Ribbon: Geometry > Horizontal > Arcs split button

Arc From Element constructs an arc based on a selected base element that controls tangency at one end. The construct may also include an optional spiral transition or arc transition (2 center curve).

Select a base element to determine tangency, and define arc parameters to define the arc in a variety of methods.

Workflow

Any of the inputs can be locked in the dialog at any time. Locking some values may limit or otherwise affect the other values.

Select the base element.
Use one of the following methods to Enter Offset:
- As you move the cursor, a value is displayed on the prompt. Data point at the desired value.
- Enter a value for Arc Length and strike the Enter key then data point.
Select start point. This is the point of tangency from the base element or its offset.
Use one of the following methods to set the Through Point or Radius (navigate the options by striking the left or right arrow keys):
- As you move the cursor, a value is displayed on the prompt. Data point at the desired value.
- Enter a value for Radius and strike the Enter key then data point.
- Enter a value for Through Point and strike the Enter key then data point.
Use one of the following methods to Define Arc Length:
- As you move the cursor, a value is displayed on the prompt. Data point at the desired value.
- Enter a value for Arc Length and strike the Enter key then data point.
To trim the base element at the intersection with the arc or to extend the element to intersect with the arc, strike the up or down arrow keys to choose a Trim/Extend option.

Dialog Customization

Right-click on the dialog to customize it for specific tasks or user preferences.

Curve Transitions

The curve construction made from this tool can include a transition between the selected reference element and the curve. The transition options available are:

None No transition (only the central simple curve is constructed)
Spiral A Spiral (curve construction is created)

Values that can be used to create the spiral are listed here.

Double Spiral Use this tool to create two spirals; the first of which transitions in same hand as a reference element starting at the reference element radius and transitioning to infinity. The second spiral transition from infinity to the radius of the new curve and is opposite hand. Although this curved reference element is the most common use case, a double spiral can be used anywhere that is needed.

Note: This is most often used when the reference element is itself a curve and of opposite hand.

Curve Constructs a 2 center curve (the transition curve is defined by radius and length)
Arc Ratio Constructs a 2 center curve (the transition length is defined by a ratio of the central curve)

Manipulators

Use Power Selector to select the line created to see edit manipulators.

When the line is placed without snaps and without Civil Accudraw constraints, you will see the onscreen manipulators as shown above. The manipulators can be used to edit the line as follows:

Transition parameters Text manipulators
Offset Text manipulator and drag handle
Radius Text manipulator
End direction text manipulator and drag handle
Arc length drag handle

Properties

Rule data is also accessible in the properties of the arc. Select the arc and click Element > Information, or open the Items browser. Most data in the property pane can be edited to change the arc definition.

Custom Tools

These pre-customized versions provide a simplified prompt sequence for many common construction tools. Right-click on the Arc from Element icon then choose Show/Hide Arc from Element Tools to access the following options:

Simple Arc from Element Creates a simple radius arc without any transition to another element, Offset locked at zero
2Center Arc from Element Creates an arc with an arc transition from another element, Offset locked at zero
Spiral Arc from Element Creates an arc with a spiral transition from another element, Offset locked at zero
Reverse Spiral Arc from Element Creates an arc with a reverse spiral transition to another element, applicable only when the From element is a curve of opposite hand, Offset locked at zero