IBezierCurve Interface

Provides access to members that identify third degree bezier curve segments and defines their properties.

Description

A Bezier Curve is a non-linear Segment defined by four control points. The bezier curve starts at control point 0 and ends at control point 3. Control points 0 and 1 define the tangent at the from point and control points 2 and 3 define the tangent at the to point. The length of these tangent lines and position of the control points determines the shape of the created bezier curve.

When To Use

The IBezierCurve interface is used to define the properties/behavior of a Bezier Curve. For example, use the methods in this interface to put control points to define a Bezier Curve object or query an existing Bezier Curve object to get its four control points.

Members

	Name	Description
	Degree	The degree of the Bezier curve. For third degree Beziers, this is always 3.
	Dimension	The topological dimension of this geometry.
	Envelope	Creates a copy of this geometry's envelope and returns it.
	FromPoint	The 'from' point of the curve.
	GeometryType	The type of this geometry.
	GeoNormalize	Shifts longitudes, if need be, into a continuous range of 360 degrees.
	GeoNormalizeFromLongitude	Normalizes longitudes into a continuous range containing the longitude. This method is obsolete.
	GetSubcurve	Extracts a portion of this curve into a new curve.
	IsClosed	Indicates if 'from' and 'to' points (of each part) are identical.
	IsEmpty	Indicates whether this geometry contains any points.
	Length	The length of the curve.
	Project	Projects this geometry into a new spatial reference.
	PutCoord	Sets the specified (0 <= index < 4) control point of this Bezier curve.
	PutCoords	Sets this Bezier curve's control points from an array of between 1 to 4 input points.
	PutWKSCoords	Sets this Bezier curve's control points from the array of 4 input point structures.
	QueryChordLengthTangentAtFrom	Returns tangent vector at 'from' point, based on chord length parametrization; and whether it has been set by user or by smoothing process.
	QueryChordLengthTangentAtTo	Returns tangent vector at 'to' point, based on chord length parametrization; and whether it has been set by user or by smoothing process.
	QueryCoord	Copies the specified control point of this Bezier curve into the input point.
	QueryCoords	Copies this Bezier curve's control points into the array of 4 existing points.
	QueryEnvelope	Copies this geometry's envelope properties into the specified envelope.
	QueryFromPoint	Copies this curve's 'from' point to the input point.
	QueryInflectionPoint	Finds inflection point; sets it empty if none exists.
	QueryNormal	Constructs a line normal to a curve from a point at a specified distance along the curve.
	QueryPoint	Copies to outPoint the properties of a point on the curve at a specified distance from the beginning of the curve.
	QueryPointAndDistance	Finds the point on the curve closest to inPoint, then copies that point to outPoint; optionally calculates related items.
	QueryTangent	Constructs a line tangent to a curve from a point at a specified distance along the curve.
	QueryToPoint	Copies the curve's 'to' point into the input point.
	QueryWKSCoords	Copies this Bezier curve's control points into the array of 4 existing point structures.
	ReverseOrientation	Reverses the parameterization of the curve ('from' point becomes 'to' point, first segment becomes last segment, etc).
	SetChordLengthTangentAtFrom	Establishes tangent vector at 'from' point, based on chord length parametrization; and sets flag whether it has been set by user or by smoothing process.
	SetChordLengthTangentAtTo	Establishes tangent vector at 'to' point, based on chord length parametrization; and sets flag whether it has been set by user or by smoothing process.
	SetEmpty	Removes all points from this geometry.
	SnapToSpatialReference	Moves points of this geometry so that they can be represented in the precision of the geometry's associated spatial reference system.
	SpatialReference	The spatial reference associated with this geometry.
	ToPoint	The 'to' point of the curve.

IBezierCurve.Degree Property

The degree of the Bezier curve. For third degree Beziers, this is always 3.

Public ReadOnly Property Degree As Integer

public int Degree {get;}

Description

Returns the degree of the Bezier Curve. Currently, all Bezier Curves have a degree of 3 by definition.

IBezierCurve.PutCoord Method

Sets the specified (0 <= index < 4) control point of this Bezier curve.

Public Sub PutCoord ( _
    ByVal Index As Integer, _
    ByVal controlPoint As IPoint _
)

public void PutCoord (
    int Index,
    IPoint controlPoint
);

Description

Places a specific control Point into a bezier curve. Control point 0 is the FromPoint of the Bezier curve (also the From tangent's FromPoint), control point 1 is the From tangent's ToPoint, control point 2 is the To tangent's FromPoint, and control point 3 is the ToPoint of the Bezier curve (also the To tangent's ToPoint).

Remarks

Use PutCoords to set all control points simultaneously. PutCoord should not be use to create a new BezierCurve, use PutCoords instead. PutCoord should only be use to modify an existing and well define BezierCurve.

BezierCurve PutCoord Example

IBezierCurve.PutCoords Method

Sets this Bezier curve's control points from an array of between 1 to 4 input points.

Public Sub PutCoords ( _
    ByVal numPoints As Integer, _
    ByRef controlPoints As IPoint _
)

public void PutCoords (
    int numPoints,
    ref IPoint controlPoints
);

Description

It is recommended that the IBezierCurveGEN::PutCoords OLE Automation compliant version of this method be used instead of this version.

Remarks

Use PutCoord to set a single control point.

BezierCurve PutCoords Example

IBezierCurve.PutWKSCoords Method

Sets this Bezier curve's control points from the array of 4 input point structures.

Public Sub PutWKSCoords ( _
    ByRef controlPoints As WKSPoint _
)

public void PutWKSCoords (
    ref WKSPoint controlPoints
);

IBezierCurve.QueryChordLengthTangentAtFrom Method

Returns tangent vector at 'from' point, based on chord length parametrization; and whether it has been set by user or by smoothing process.

Public Sub QueryChordLengthTangentAtFrom ( _
    ByVal tangent As IPoint, _
    ByRef setByUser As Boolean _
)

public void QueryChordLengthTangentAtFrom (
    IPoint tangent,
    ref bool setByUser
);

Description

Returns the ChordLength Tangent at the From Point of the BezierCurve along with a flag indicating whether this ChordLength Tangent was set by the user or defined from Control Points. The ChordLength Tangent is not the same as the internal Control Points or the Tangent at the From Point although both lie on the same line. The coordinates of the returned point are in reality a Dx and Dy which can be added to the From point in order to get the tangent.

private void QueryChordLengthTangentAtFrom()

    {

        //Control points

        IPoint[] controlPoints = new IPoint[4];

        //Bezier FromPoint / From Tangent FromPoint 

        controlPoints[0] = new ESRI.ArcGIS.Geometry.Point();

        //From Tangent ToPoint 

        controlPoints[1] = new ESRI.ArcGIS.Geometry.Point();

        //To Tangent FromPoint 

        controlPoints[2] = new ESRI.ArcGIS.Geometry.Point();

        //Bezier To Point / To Tangent ToPoint 

        controlPoints[3] = new ESRI.ArcGIS.Geometry.Point();

        //Define the Bezier Control Points.  This is a simple S-Curve. 

        controlPoints[0].PutCoords(100, 100);

        controlPoints[1].PutCoords(150, 200);

        controlPoints[2].PutCoords(250, 0);

        controlPoints[3].PutCoords(400, 100);

        IBezierCurveGEN bezierCurve = new BezierCurve();

        bezierCurve.PutCoords(ref controlPoints);

        //QueryChordLengthTangentAtFrom

        IPoint tangentPoint = new ESRI.ArcGIS.Geometry.Point();

        bool isUserSet = false;

        bezierCurve.QueryChordLengthTangentAtFrom(tangentPoint, ref isUserSet);

        //Report

        String report = "QueryChordLengthTangentAtFrom \n" +

                        "Point At From : " + tangentPoint.X + " , " + tangentPoint.Y + "\n" +

                        "Set by the user : " + isUserSet;

        System.Windows.Forms.MessageBox.Show(report);

    }

IBezierCurve.QueryChordLengthTangentAtTo Method

Returns tangent vector at 'to' point, based on chord length parametrization; and whether it has been set by user or by smoothing process.

Public Sub QueryChordLengthTangentAtTo ( _
    ByVal tangent As IPoint, _
    ByRef setByUser As Boolean _
)

public void QueryChordLengthTangentAtTo (
    IPoint tangent,
    ref bool setByUser
);

Description

Returns the ChordLength Tangent at the To Point of the BezierCurve along with a flag indicating whether this ChordLength Tangent was set by the user or defined from Control Points. The ChordLength Tangent is not the same as the internal Control Points or the Tangent at the To Point although both lie on the same line. The coordinates of the returned point are in reality a Dx and Dy which can be added to the To point in order to get the tangent.

private void QueryChordLengthTangentAtTo()

    {

        //Control points

        IPoint[] controlPoints = new IPoint[4];

        //Bezier FromPoint / From Tangent FromPoint 

        controlPoints[0] = new ESRI.ArcGIS.Geometry.Point();

        //From Tangent ToPoint 

        controlPoints[1] = new ESRI.ArcGIS.Geometry.Point();

        //To Tangent FromPoint 

        controlPoints[2] = new ESRI.ArcGIS.Geometry.Point();

        //Bezier To Point / To Tangent ToPoint 

        controlPoints[3] = new ESRI.ArcGIS.Geometry.Point();

        //Define the Bezier Control Points.  This is a simple S-Curve. 

        controlPoints[0].PutCoords(100, 100);

        controlPoints[1].PutCoords(150, 200);

        controlPoints[2].PutCoords(250, 0);

        controlPoints[3].PutCoords(400, 100);

        IBezierCurveGEN bezierCurve = new BezierCurve();

        bezierCurve.PutCoords(ref controlPoints);

        //QueryChordLengthTangentAtTo

        IPoint tangentPoint = new ESRI.ArcGIS.Geometry.Point();

        bool isUserSet = false;

        bezierCurve.QueryChordLengthTangentAtTo(tangentPoint, ref isUserSet);

        //Report

        String report = "QueryChordLengthTangentAtTo \n" +

                        "Point At From : " + tangentPoint.X + " , " + tangentPoint.Y + "\n" +

                        "Set by the user : " + isUserSet;

        System.Windows.Forms.MessageBox.Show(report);

    }

IBezierCurve.QueryCoord Method

Copies the specified control point of this Bezier curve into the input point.

Public Sub QueryCoord ( _
    ByVal Index As Integer, _
    ByVal controlPoint As IPoint _
)

public void QueryCoord (
    int Index,
    IPoint controlPoint
);

Description

Use QueryCoord to obtain a specific bezier control Point. Any of the four bezier control points (0 to 3) can be queried.

Remarks

Use QueryCoords to get all of the control points.

BezierCurve QueryCoord Example

IBezierCurve.QueryCoords Method

Copies this Bezier curve's control points into the array of 4 existing points.

Public Sub QueryCoords ( _
    ByRef controlPoints As IPoint _
)

public void QueryCoords (
    ref IPoint controlPoints
);

Description

QueryCoords returns all four of the BezierCurve control points into an array of 4 Points.

Remarks

Use QueryCoord to get a specific control point.

BezierCurve QueryCoords Example

IBezierCurve.QueryInflectionPoint Method

Finds inflection point; sets it empty if none exists.

Public Sub QueryInflectionPoint ( _
    ByVal inflectionPoint As IPoint _
)

public void QueryInflectionPoint (
    IPoint inflectionPoint
);

Description

Returns the first Inflection Point of the Bezier Curve, or returns an Empty Point if no Inflection Point Exists. An Inflection Point occurs where the sign of the Curvature changes.

Remarks

Most Bezier Curves have 0 or 1 Inflection Points, but a few constructions result in Bezier Curves with 2 Inflection Points. For these Bezier Curve, the only way to find both Inflection Points is to Reverse the Orientation of the Bezier Curve and call QueryInflectionPoint a second time. If the Inflection Points are not equal, the Bezier Curve has two Inflection Points, otherwise, it only has a single Inflection Point.

BezierCurve QueryInflectionPoint Example

private void QueryInflectionPoint()

    {

        //Control points

        IPoint[] controlPoints = new IPoint[4];

        //Bezier FromPoint / From Tangent FromPoint 

        controlPoints[0] = new ESRI.ArcGIS.Geometry.Point();

        //From Tangent ToPoint 

        controlPoints[1] = new ESRI.ArcGIS.Geometry.Point();

        //To Tangent FromPoint 

        controlPoints[2] = new ESRI.ArcGIS.Geometry.Point();

        //Bezier To Point / To Tangent ToPoint 

        controlPoints[3] = new ESRI.ArcGIS.Geometry.Point();

        //Define the Bezier Control Points.  This is a simple S-Curve. 

        controlPoints[0].PutCoords(100, 100);

        controlPoints[1].PutCoords(150, 200);

        controlPoints[2].PutCoords(250, 0);

        controlPoints[3].PutCoords(400, 100);

        IBezierCurveGEN bezierCurve = new BezierCurve();

        bezierCurve.PutCoords(ref controlPoints);

        //Report control Point

        IPoint[] outControlPoints = new IPoint[4];

        for (int i = 0; i < controlPoints.Length; i++)

        {

            outControlPoints[i] = new ESRI.ArcGIS.Geometry.Point();

        }

        bezierCurve.QueryCoords(ref outControlPoints);

        String report = "Control Points \n";

        for (int i = 0; i < outControlPoints.Length; i++)

        {

            report = report + outControlPoints[i].X + " , " + outControlPoints[i].Y + " \n";

        }

        IPoint infelctionPoint = new ESRI.ArcGIS.Geometry.Point(); ;

        bezierCurve.QueryInflectionPoint(infelctionPoint);

        report = report + "Inflection Point : " + infelctionPoint.X + " , " + infelctionPoint.Y;

        System.Windows.Forms.MessageBox.Show(report);

    }

IBezierCurve.QueryWKSCoords Method

Copies this Bezier curve's control points into the array of 4 existing point structures.

Public Sub QueryWKSCoords ( _
    ByRef controlPoints As WKSPoint _
)

public void QueryWKSCoords (
    ref WKSPoint controlPoints
);

IBezierCurve.SetChordLengthTangentAtFrom Method

Establishes tangent vector at 'from' point, based on chord length parametrization; and sets flag whether it has been set by user or by smoothing process.

Public Sub SetChordLengthTangentAtFrom ( _
    ByVal tangent As IPoint, _
    ByVal setByUser As Boolean _
)

public void SetChordLengthTangentAtFrom (
    IPoint tangent,
    bool setByUser
);

Description

Sets the ChordLength Tangent at the From Point of the BezierCurve. The ChordLength Tangent is not the same as the internal Control Points or the Tangent at the From Point although both lie on the same line.

IBezierCurve.SetChordLengthTangentAtTo Method

Establishes tangent vector at 'to' point, based on chord length parametrization; and sets flag whether it has been set by user or by smoothing process.

Public Sub SetChordLengthTangentAtTo ( _
    ByVal tangent As IPoint, _
    ByVal setByUser As Boolean _
)

public void SetChordLengthTangentAtTo (
    IPoint tangent,
    bool setByUser
);

Description

Sets the ChordLength Tangent at the To Point of the BezierCurve. The ChordLength Tangent is not the same as the internal Control Points or the Tangent at the To Point although both lie on the same line.

Inherited Interfaces

Interfaces	Description
ICurve	Provides access to properties and methods of all 1 dimensional curves (polylines, segments, boundaries of polygons, etc.).
IGeometry	Provides access to members that describe properties and behavior of all geometric objects.

Classes that implement IBezierCurve

Classes	Description
BezierCurve	A cubic Bezier curve defined between two points; optionally has measure, height and ID attributes at each endpoint.

Remarks

IBezierCurve Example