To Add Floating Curves to Alignments

Add floating curves to build constraint-based alignment geometry for the areas of your design that require maintaining tangency.

Tutorial Exercise: Adding Floating Curves to an Alignment

To add a floating curve (from entity, radius, through point)

Add a floating curve, defined by a specified radius and angle range, from an existing entity to a specified end point.

This curve supports both compound and reverse solutions.

The following illustration shows a floating curve attached to a fixed line and two possible solutions for a given radius and point:

Click here to view illustration

The following illustration shows a floating compound curve attached to a curve and four possible solutions for a given radius and pass-through point. The illustration also shows variables for greater than and less than 180 degrees and compound and reverse variables:

Click here to view illustration

1. Click the alignment. Click Alignment tabModify panelGeometry Editor.
2. On the Alignment Layout Tools toolbar, click Floating Curve (From Entity, Radius, Through Point).
3. Select the end of the entity to which you want to add the floating curve.
4. Specify a radius, or enter D to specify the degree of curvature.

   Specify a new value, or press Enter to accept the value that is displayed on the command line.

   • If the alignment has design criteria applied to it, the minimum value for the current design speed is displayed.
   • If the alignment does not have design criteria applied to it, the default value specified in the curve and spiral settings is displayed.
   Note: To calculate the radius or degree of curvature using other known curve parameters, enter 'CCALC to open the Curve Calculator.
5. Specify whether the curve solution angle is either greater than or less than 180 degrees. A preview curve is displayed.
   Note: If the attachment entity is a curve, you are prompted to specify either a compound curve or a reverse curve.
6. Specify the pass-through point.

To add a floating curve (from entity end, through point)

Add a floating curve from the end of an existing entity to a specified pass-through point.

The attachment entity (1) and pass-through point (2) determine the curve radius. You cannot edit the radius for this type of curve.

The result is a floating curve that is always tangent to the entity it is attached to.

1. Click the alignment. Click Alignment tabModify panelGeometry Editor.
2. On the Alignment Layout Tools toolbar, click Floating Curve (From Entity End, Through Point).
3. Select the end of the entity to which you want to add the floating curve.
4. Specify the end point. A curve preview is displayed.

To add a floating curve attached (from entity end, radius, length)

Add a floating curve entity that is defined by the entity end to which it is attached, the radius, and the length by specifying the entity end where you want to add the curve.

This curve is not defined by a pass-through point, so the entire curve moves with the entity to which it is attached.

1. Click the alignment. Click Alignment tabModify panelGeometry Editor.
2. On the Alignment Layout Tools toolbar, click Floating Curve (From Entity End, Radius, Length).
3. Select the end of the entity to which you want to add the floating curve.
4. Specify the curve direction: either clockwise or counter-clockwise.
5. Specify a radius, or enter D to specify the degree of curvature.

   Specify a new value, or press Enter to accept the value that is displayed on the command line.

   • If the alignment has design criteria applied to it, the minimum value for the current design speed is displayed.
   • If the alignment does not have design criteria applied to it, the default value specified in the curve and spiral settings is displayed.
   Note: To calculate the radius or degree of curvature using other known curve parameters, enter 'CCALC to open the Curve Calculator.
6. Specify the length or [deltaAngle/Tanlen/Chordlen/midOrd/External].

To add a floating curve (from entity, through point, direction at point)

Add a floating curve with a specified pass-through point and direction at the pass-through point to an existing entity.

The attachment entity (1), pass-through point (2), and direction (3) determine the curve attachment point and radius. You cannot edit the radius for this type of curve.

The result is a floating curve that is always tangent to the entity it is attached to.

1. Click the alignment. Click Alignment tabModify panelGeometry Editor.
2. On the Alignment Layout Tools toolbar, click Floating Curve (From Entity, Through Point, Direction At Point).
3. Specify the entity to which you want to add the floating curve.
4. Specify the end point.
5. Specify the direction at the end point or specify bearing or azimuth.

To create a floating curve by best fit

Add the most probable floating curve through a series of AutoCAD Civil 3D points, AutoCAD points, existing entities, or clicks on screen.

The location of the curve start point on the attachment entity (1) is determined by the path through the selected regression points (2).

1. Click the alignment. Click Alignment tabModify panelGeometry Editor.
2. On the Alignment Layout Tools toolbar, click Floating Curve - Best Fit.
3. Select an entity for the start point and direction.

   If you select the beginning of the entity, the best fit curve will precede the entity. If you select the end of the entity, the best fit curve will succeed the entity.

4. In the Curve By Best Fit dialog box, select one of the following:
   • From AutoCAD Points. Select two or more AutoCAD points.
   • From COGO Points. Select two or more AutoCAD Civil 3D points. Enter G to select a point group or N to enter points by number.
   • From Entities. Specify the tessellation and mid-ordinate tolerance settings. Select one or more of the entity types listed on the command line. If you selected a profile object, specify the starting and ending station on the Specify Station Range dialog box.
   • By Clicking On The Screen. Select at least two points. You can use OSNAP or transparent commands to select points.

   As you select points in the drawing window, an X marks each regression point and a temporary, dashed curve is displayed in real time. You must select at least two non-collinear regression points. Press Enter to complete the command.

5. In the Panorama window, use the Regression Data vista to make changes to the regression points.

   As you highlight a row in the Regression Data vista, the corresponding regression point in the drawing window is highlighted in red.

6. Create the curve:
   • Click to create the curve and keep the Regression Data vista open.
   • Click to create the curve and close the Regression Data vista.