How to use some basic properties and methods on ICircularArc (ArcObjects .NET 10.8 SDK)

Using some basic properties and methods on ICircularArc

Do the following steps to use properties and methods on ICircularArc:

Define the center point of the circle.
Define a quarter circle (Pi/2 radians) from Pi/3 (60 degrees) to 5*Pi/6 (150 degrees) in a counterclockwise direction with a radius of 100 and a center at (0,0).
Set circularArc equal to the complement circular arc, which can be defined by circularArc.PutCoordsByAngle(origin, Pi/3, -3*Pi/2, 100).
Query the center, start, and end points as well as orientation. These are the points required by PutCoords, but the ArcOrientation still needs to be checked against special cases.
Set orientation to the IsCCW value unless the start and end Points are the same.
Recreate the CircularArc using PutCoords.
Construct the same arc using ConstructThreePoints.
Change the radius so that the new radius is the distance between the origin and the new point. Basically, it places the arc on the embedded circle with the same center point and the new input point.
Query some of the properties of the arc.

The following code example shows how to work with some basic properties and methods of ICircularArc:

[C#]

public void DemonstrateCircularArcs()
{
    IPoint origin=new ESRI.ArcGIS.Geometry.Point();
    origin.PutCoords(0, 0);
    ICircularArc circularArc=new CircularArcClass();
    circularArc.PutCoordsByAngle(origin, Math.PI / 3, Math.PI / 2, 100);
    OutputArcProperties(circularArc);
    circularArc.Complement();
    OutputArcProperties(circularArc);
    IPoint startPoint=new ESRI.ArcGIS.Geometry.Point();
    IPoint endPoint=new ESRI.ArcGIS.Geometry.Point();
    bool isCCW=false;
    bool isMinor=false;
    circularArc.QueryCoords(origin, startPoint, endPoint, ref isCCW, ref isMinor);
    //Set orientation to the IsCCW value unless start and end points are the same.
    esriArcOrientation arcOrientation=0;
    if ((circularArc.IsClosed) || (circularArc.Length < (Math.Pow(10,  - 12))))
    {
        if (isMinor)
        {
            arcOrientation=esriArcOrientation.esriArcMinor;
        }
        else
        {
            arcOrientation=esriArcOrientation.esriArcMajor;
        }
        if (isCCW)
        {
            arcOrientation=esriArcOrientation.esriArcCounterClockwise;
        }
        else
        {
            arcOrientation=esriArcOrientation.esriArcClockwise;
        }
    }
    //Note: The start and end points must be the same distance (the radius)
    // from the center point. Otherwise, an empty geometry is created.
    circularArc.PutCoords(origin, startPoint, endPoint, arcOrientation);
    OutputArcProperties(circularArc);

    IPoint throughPoint=new ESRI.ArcGIS.Geometry.Point();
    //This is a point on the arc.
    throughPoint.PutCoords(0,  - 100);
    //Changes the radius so that the new radius is the distance between the origin and the new point.
    IConstructCircularArc threePointArcConstruction=new CircularArcClass();
    threePointArcConstruction.ConstructThreePoints(startPoint, throughPoint,
        endPoint, false);
    ICircularArc threePointArc=threePointArcConstruction as ICircularArc;
    OutputArcProperties(threePointArc);
    //Query only the center point into origin.
    threePointArc.QueryCenterPoint(origin);
    throughPoint.PutCoords(0, 150);
    threePointArc.PutRadiusByPoint(throughPoint);
    //Query the center point, from angle, central angle, and radius.
    //This is the same information needed to use PutCoordsByAngle.
    double angelFromArc=0;
    double centerAngel=0;
    double radius=0;
    threePointArc.QueryCoordsByAngle(origin, ref angelFromArc, ref centerAngel, ref
        radius);
    OutputArcProperties(threePointArc);
}

private void OutputArcProperties(ICircularArc circularArc)
{
    String report="Center Point: (" + circularArc.CenterPoint.X + ", " +
        circularArc.CenterPoint.Y + ")" + "\n" + "From Point: (" +
        circularArc.FromPoint.X + ", " + circularArc.FromPoint.Y + ")" + "\n" + 
        "To Point: (" + circularArc.ToPoint.X + ", " + circularArc.ToPoint.Y + ")" +
        "\n" + "From Angle: " + circularArc.FromAngle + "\n" + "Central Angle: " +
        circularArc.CentralAngle + "\n" + "To Angle: " + circularArc.ToAngle + "\n" 
        + "Radius: " + circularArc.Radius + "\n" + "Chord Height: " +
        circularArc.ChordHeight + "\n" + "IsCounterClockwise: " +
        circularArc.IsCounterClockwise + "\n" + "IsMinor: " + circularArc.IsMinor + 
        "\n" + "IsLine: " + circularArc.IsLine + "\n" + "IsPoint: " +
        circularArc.IsPoint + ")";
    //IsLine and IsPoint check for degenerate cases of CircularArcs.
    System.Windows.Forms.MessageBox.Show(report);
}

[VB.NET]

Public Sub DemonstrateCircularArcs()
    Dim pCArc As ICircularArc
    pCArc=New CircularArc
    Dim pOrigin As IPoint
    pOrigin=New Point
    Dim Pi As Double
    Dim pStartPoint As IPoint
    Dim pEndPoint As IPoint
    pStartPoint=New Point
    pEndPoint=New Point
    Dim bIsCCW As Boolean
    Dim bIsMinor As Boolean
    Dim CArcFromAngle As Double
    Dim CArcCenterAngle As Double
    Dim CArcRadius As Double
    Dim CArcOrientation As esriArcOrientation
    Dim pConstCArc2 As IConstructCircularArc
    Dim pCArc2 As ICircularArc
    Dim pThroughPoint As IPoint
    pCArc2=New CircularArc
    pThroughPoint=New Point
    pConstCArc2=pCArc2
    'This defines the constant Pi=3.14159265358979.
    Pi=4 * Math.Atan(1)
    'Define the center point of the circle.
    pOrigin.PutCoords(0, 0)
    'Define a quarter circle (Pi/2 radians) from Pi/3 (60 degress)
    ' to 5*Pi/6 (150 degrees) in a counterclockwise direction
    ' with a radius of 100 and a center at (0,0).
    pCArc.PutCoordsByAngle(pOrigin, Pi / 3, Pi / 2, 100)
    OutputCArcProperties(pCArc)
    'Set pCArc equal to the complement circular arc,
    'which could be defined by pCArc.PutCoordsByAngle pOrigin, Pi/3, -3*Pi/2, 100.
    pCArc.Complement()
    OutputCArcProperties(pCArc)
    'Query the center, start, and end points as well as orientation.
    'These are the points required by PutCoords, but the ArcOrientation
    ' still needs to be checked against special cases.
    pCArc.QueryCoords(pOrigin, pStartPoint, pEndPoint, bIsCCW, bIsMinor)
    'Set orientation to the IsCCW value unless start and end points are the same.
    If (pCArc.IsClosed) Or (pCArc.Length < (10 ^ -12)) Then
        If bIsMinor Then
            CArcOrientation=esriArcOrientation.esriArcMinor
        Else
            CArcOrientation=esriArcOrientation.esriArcMajor
        End If
    Else
        If bIsCCW Then
            CArcOrientation=esriArcOrientation.esriArcCounterClockwise
        Else
            CArcOrientation=esriArcOrientation.esriArcClockwise
        End If
    End If
    'Recreate the CircularArc using PutCoords.
    'Note: The start and end points must be the same distance (the radius)
    ' from the center point. Otherwise, an empty geometry is created.
    pCArc.PutCoords(pOrigin, pStartPoint, pEndPoint, CArcOrientation)
    OutputCArcProperties(pCArc)
    'Now you will construct the same arc using ConstructThreePoints.
    pThroughPoint.PutCoords(0, -100) 'This is a point on the arc.
    pConstCArc2.ConstructThreePoints(pStartPoint, pThroughPoint, pEndPoint, False)
    OutputCArcProperties(pCArc2)
    'Query only the center point into pOrigin.
    pCArc2.QueryCenterPoint(pOrigin)
    pThroughPoint.PutCoords(0, 150)
    'Change the radius so that the new radius is the distance between the origin
    ' and the new point. Basically, it places the arc on the embedded circle
    ' with the same center point and the new input point.
    pCArc2.PutRadiusByPoint(pThroughPoint)
    'Query the center point, from angle, central angle, and radius.
    'This is the same information needed to use PutCoordsByAngle.
    pCArc2.QueryCoordsByAngle(pOrigin, CArcFromAngle, CArcCenterAngle, CArcRadius)
    OutputCArcProperties(pCArc2)
End Sub


Private Sub OutputCArcProperties(ByVal pInCArc As ICircularArc)
    MsgBox("Center Point: (" & pInCArc.CenterPoint.X & ", " & _
           pInCArc.CenterPoint.Y & ")" & vbCrLf & _
           "From Point: (" & pInCArc.FromPoint.X & ", " & _
           pInCArc.FromPoint.Y & ")" & vbCrLf & _
           "To Point: (" & pInCArc.ToPoint.X & ", " & _
           pInCArc.ToPoint.Y & ")" & vbCrLf & _
           "From Angle: " & pInCArc.FromAngle & vbCrLf & _
           "Central Angle: " & pInCArc.CentralAngle & vbCrLf & _
           "To Angle: " & pInCArc.ToAngle & vbCrLf & _
           "Radius: " & pInCArc.Radius & vbCrLf & _
           "Chord Height: " & pInCArc.ChordHeight & vbCrLf & _
           "IsCounterClockwise: " & pInCArc.IsCounterClockwise & vbCrLf & _
           "IsMinor: " & pInCArc.IsMinor & vbCrLf & _
           "IsLine: " & pInCArc.IsLine & vbCrLf & _
           "IsPoint: " & pInCArc.IsPoint)
    'IsLine and IsPoint check for degenerate cases of CircularArcs.
End Sub

To use the code in this topic, reference the following assemblies in your Visual Studio project. In the code files, you will need using (C#) or Imports (VB .NET) directives for the corresponding namespaces (given in parenthesis below if different from the assembly name):

ESRI.ArcGIS.Geometry

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