Create Arc Length Dimensions (.NET)

Arc length dimensions measure the length along an arc and displays the dimension text with an arc symbol that is either above or proceeds it. You might use an arc length dimension when you need to dimension the actual length of an arc instead of just distance between its start and end points.

You create an arc length radius dimension by creating an instance of an ArcDimension object. When you create an instance of an ArcDimension object, it requires a set of parameters that define the dimension. The following parameters must be supplied when you create a new ArcDimension object:

Note: The DIMARCSYM system variable controls if an arc symbol is displayed and where it is displayed in relation to the dimension text.

Create an arc length dimension

This example creates an arc length dimension in Model space.

VB.NET

Imports Autodesk.AutoCAD.Runtime
Imports Autodesk.AutoCAD.ApplicationServices
Imports Autodesk.AutoCAD.DatabaseServices
Imports Autodesk.AutoCAD.Geometry
 
<CommandMethod("CreateArcLengthDimension")> _
Public Sub CreateArcLengthDimension()
    '' Get the current database
    Dim acDoc As Document = Application.DocumentManager.MdiActiveDocument
    Dim acCurDb As Database = acDoc.Database

    '' Start a transaction
    Using acTrans As Transaction = acCurDb.TransactionManager.StartTransaction()

        '' Open the Block table for read
        Dim acBlkTbl As BlockTable
        acBlkTbl = acTrans.GetObject(acCurDb.BlockTableId, _
                                     OpenMode.ForRead)

        '' Open the Block table record Model space for write
        Dim acBlkTblRec As BlockTableRecord
        acBlkTblRec = acTrans.GetObject(acBlkTbl(BlockTableRecord.ModelSpace), _
                                        OpenMode.ForWrite)

        '' Create an arc length dimension
        Using acArcDim As ArcDimension = New ArcDimension(New Point3d(4.5, 1.5, 0), _
                                                          New Point3d(8, 4.25, 0), _
                                                          New Point3d(0, 2, 0), _
                                                          New Point3d(5, 7, 0), _
                                                          "<>", _
                                                          acCurDb.Dimstyle)

            '' Add the new object to Model space and the transaction
            acBlkTblRec.AppendEntity(acArcDim)
            acTrans.AddNewlyCreatedDBObject(acArcDim, True)
        End Using

        '' Commit the changes and dispose of the transaction
        acTrans.Commit()
    End Using
End Sub

C#

using Autodesk.AutoCAD.Runtime;
using Autodesk.AutoCAD.ApplicationServices;
using Autodesk.AutoCAD.DatabaseServices;
using Autodesk.AutoCAD.Geometry;
 
[CommandMethod("CreateArcLengthDimension")]
public static void CreateArcLengthDimension()
{
    // Get the current database
    Document acDoc = Application.DocumentManager.MdiActiveDocument;
    Database acCurDb = acDoc.Database;

    // Start a transaction
    using (Transaction acTrans = acCurDb.TransactionManager.StartTransaction())
    {
        // Open the Block table for read
        BlockTable acBlkTbl;
        acBlkTbl = acTrans.GetObject(acCurDb.BlockTableId,
                                        OpenMode.ForRead) as BlockTable;

        // Open the Block table record Model space for write
        BlockTableRecord acBlkTblRec;
        acBlkTblRec = acTrans.GetObject(acBlkTbl[BlockTableRecord.ModelSpace],
                                        OpenMode.ForWrite) as BlockTableRecord;

        // Create an arc length dimension
        using (ArcDimension acArcDim = new ArcDimension(new Point3d(4.5, 1.5, 0),
                                                        new Point3d(8, 4.25, 0),
                                                        new Point3d(0, 2, 0),
                                                        new Point3d(5, 7, 0),
                                                        "<>",
                                                        acCurDb.Dimstyle))
        {

            // Add the new object to Model space and the transaction
            acBlkTblRec.AppendEntity(acArcDim);
            acTrans.AddNewlyCreatedDBObject(acArcDim, true);
        }

        // Commit the changes and dispose of the transaction
        acTrans.Commit();
    }
}

VBA/ActiveX Code Reference

Sub CreateArcLengthDimension()
    Dim dimObj As AcadDimArcLength
    Dim arcCenterPoint(0 To 2) As Double
    Dim firstPoint(0 To 2) As Double
    Dim secondPoint(0 To 2) As Double
    Dim arcPoint(0 To 2) As Double
 
    ' Define the dimension
    arcCenterPoint(0) = 4.5: arcCenterPoint(1) = 1.5: arcCenterPoint(2) = 0
    firstPoint(0) = 8: firstPoint(1) = 4.25: firstPoint(2) = 0
    secondPoint(0) = 0: secondPoint(1) = 2: secondPoint(2) = 0
    arcPoint(0) = 5: arcPoint(1) = 7: arcPoint(2) = 0
 
    ' Create the arc length dimension in Model space
    Set dimObj = ThisDrawing.ModelSpace. _
                     AddDimArc(arcCenterPoint, firstPoint, _
                     secondPoint, arcPoint)
 
    ZoomAll
End Sub

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