Road Widening using AutoCAD Civil 3D .NET API

By Partha Sarkar

In AutoCAD Civil 3D, programmatically we can create Offset Alignment using overloaded Alignment.CreateOffsetAlignment() API. Once we have created an Offset Alignment, we can call OffsetAlignmentInfo.AddWidening() to create a road widening for a specific section of the road.

Here is a C# .NET code snippet demonstrating usage of OffsetAlignmentInfo.AddWidening() API :

using (Transaction trans = db.TransactionManager.StartTransaction())
{
 
  ObjectIdCollection alignmentIdColl = civilDoc.GetAlignmentIds();
  foreach (ObjectId alignmentId in alignmentIdColl)
  {
    alignment = alignmentId.GetObject(OpenMode.ForRead) asAlignment;
    if (alignment.Name.ToString() == "Centerline (1)")
      break;
 
  }
 
  if (alignment != null)
  {
 
    // Get a AlignmentStyle Object to use in OffSet Alignment creation
    ObjectId offsetAlignmentStyleId = civilDoc.Styles.AlignmentStyles["Design Style"];
 
    if (offsetAlignmentStyleId == null)
    {
      ed.WriteMessage("nOffset Alignment Style NOT found !");
      return;
    }
 
    // Now create the OffSetAlignment
    // A negative value (offset < 0) indicates the Offset Alignment is at the left of the parent alignment.
    // A positive value (offset > 0) indicates the Offset Alignment is at the right.
    ObjectId offsetAlignmentId = Alignment.CreateOffsetAlignment("Offset_Alignment", alignment.ObjectId, -30.00, offsetAlignmentStyleId);
 
    // Open the Offset Alignment object to add road widening
    Alignment offsetAlignment = offsetAlignmentId.GetObject(OpenMode.ForWrite) asAlignment;
 
    OffsetAlignmentInfo offsetInfo1 = offsetAlignment.OffsetAlignmentInfo;
 
    // Now use AddWidening( double startStation, double endStation, double offsetDistance )
    // This method will create a specific region from startStation to endStation 
    // with slim entry transition and exit transition.
    offsetInfo1.AddWidening(200.00, 533.0, 40.0);
 
  }    
 
  trans.Commit();
}

Following picture shows how it appears in AutoCAD Civil 3D :

Hope this is useful to you!