Offset a Line Using the CAD Command Line
Use the Offset Line command alias on the CAD Command Line to create a new linestring offset (parallel) at a specified distance from an existing line. The line from which you are offsetting can be either 2D (such as a boundary, polyline, circle, or an alignment without a vertical alignment (VAL)) or 3D (such as a 3D linestring or an alignment with a VAL).
In addition, the offset can be horizontal, vertical, or both. Line segments offset from spirals (as well as smoothed segments) are chorded. Using this command (but not the pane-based Offset Line command), you can also offset just a segment (any portion) of a selected polyline.
Warning: If you offset a 3D linestring only vertically, any vertical curves it includes will be the same as the source, but if you offset both vertically and horizontally, the vertical curves will be different in length.
Prerequisites:
- Line from which to offset a new line/segment
- License; See the Subscription Plans page. For a license matrix by command, see the License page in the TBC Community. Also see View and manage licensed features.
To offset a line/segment from the CAD Command Line:
- Press [F3] or click the
icon on the Status Bar to open the CAD Command Line. - Type o or O at the command prompt, and press [Enter].
- If needed, set the Layer, Color, and/or Line style below the command prompt. These properties persist the next time you run the command.
- Pick either a line or a segment of a line to offset from in a supported graphic view (Plan, Sheet, or Cutting Plane).
- Based on the Entire object mode highlighted at the prompt, enter an offset distance or pick a point offset from the selected line, or type a keyword character to use another mode. The options are:
- Entire object - Enter E to offset the selected line (see below).
- Segment - Enter S to offset the selected segment (see below).
- For either mode, enter a horizontal offset distance or a pick a point in a graphic view at the desired distance from the selected line/segment to specify the offset distance. If you pick the offset distance graphically, this also sets the side on which the new line/segment will be drawn. If you entered a distance for the offset using the keyboard, pick a side on which to draw the offset line in the view, or press enter to accept the default Right side. The command remembers the last mode used the next time you run the command.
Note: The side is determined by the direction of the line from the start point to the end point.
- Type a vertical offset distance and press [Enter], or simply press [Enter] to accept the default of 0.0. You can also specify the vertical delta as a % or ratio of the starting elevation (depends on project setting of rise/run or vice versa).
Note: You are not prompted for a vertical offset if you are working in a Sheet View.
The offset line/segment is drawn (and will appear if the layer is not hidden).
- If you are only offsetting a segment (portion of the line), pick the start and end points of the segment, and press [Enter].
- Based on the Offset the last offset line mode highlighted at the prompt, keep pressing [Enter] to create additional offsets using the same settings, or pick another line to offset, or press [Escape] to end the command and return to a blank command prompt.
- Press [Spacebar] to rerun the command.
Scenario:
- If the reference line contains acute angles, the resulting offset line may be malformed.
- If you offset from a 3D linestring with VPIs, the VPI elevations (but not the actual VPIs) are retained in the resulting polyline. If you edit the polyline (thereby converting it into a linestring), the VPIs exist.
Dependencies:
- None; if you change the reference line any offset line/segment is not affected. Once created, the offset line is independent from the reference line.
