Creating Alignments from Objects

A common way of creating an alignment is to use the basic AutoCAD® software geometry that’s already in the drawing. You may be using someone’s “sketch,” or maybe you’ve chosen to draw the initial version of the layout this way because of the simplicity of the AutoCAD tools. Whatever the case, Civil 3D makes it fairly easy to convert simple AutoCAD entities into alignments.

To create alignments from objects in your drawing, complete the following steps:

The Exercise File can be downloaded at the end of the article  

1. Open the drawing named Alignment from Objects.dwg located in the Chapter 05 class data folder.

   Tips :Since alignment design is strictly a 2D type of design, the drawings in this chapter are not set up with multiple viewports.


2. On the Home tab of the ribbon, click AlignmentCreate Alignment From Objects.
3. When the command line prompts you to select an object, click the longest magenta polyline, labeled Jordan Court.

   Tips :Notice on the command line that the Create Alignment From Objects command accepts lines, arcs, and polylines.

4. Press Enter. A black arrow should appear on the polyline indicating the program’s guess at the direction of the alignment.
5. If the arrow is pointing toward the south, press Enter. If it is pointing north, press R and then press Enter.

   Tips :Believe it or not, the choice here is very important. The direction of the alignment will affect the configuration and labeling of many more components of this design as it progresses.

6. In the Create Alignment From Objects dialog box, do the following:
   • For Name, verify that it says Jordan Court.
   • For Type, verify that Centerline is selected.
   • For Site, verify that <None> is selected.
   • For Alignment style, verify that Proposed is selected.
   • For Alignment label set, verify that _No Labels is selected.
   • Uncheck the box next to Add curves between tangents.
   • Verify that the box next to Erase existing entities is Checked.
   • Click OK.
7. Click the newly created alignment, and then click one of the magenta polylines. Notice how the polyline grips are different from the alignment grips (see Figure 5.2). Experiment with moving the grips and compare the behavior of a Civil 3D alignment with the behavior of a polyline.

   Figure 5.2  The object with the dark blue grips is a polyline, and the object with the light blue grips is an alignment. Alignments have more types of grips that enable more geometric editing functionality.

8. Repeat steps 2 through 6 to create the Madison Lane and Logan Court alignments.

Alignments Are Smarter

As you investigate the grip editing behavior of the alignment versus the polyline, what do you find? You should notice that the alignment wants to follow a very basic geometric rule that the polyline doesn’t worry about too much: maintaining tangency. Whether you move or stretch a straight line portion (aka tangent) or modify a curve, the adjacent lines and curves morph themselves to remain tangent (shown here). This is a good thing because driving your car down a road where the curves and lines are not tangent could be hazardous to your health.

Download Exercise File :

• Chapter 05 - Creating Alignments from Objects - Metric     --- ( 829.51 KB )
• Chapter 05 - Creating Alignments from Objects - Imperial  --- ( 740.98 KB )
• Civil 3D 2014 All Exercise Files - Chapter 05