ArcGIS Developer Help

IVector3D Interface

Available with ArcGIS Engine, ArcGIS Desktop, and ArcGIS Server.

[C#]

 

        private static object _missing = Type.Missing;

        public static IGeometry GetMultiPatchGeometry()

        {

            const double ConeBaseDegrees = 360.0;

            const int ConeBaseDivisions = 36;

            const double VectorComponentOffset = 0.0000001;

            const double ConeBaseRadius = 6;

            const double ConeBaseZ = 0.0;

            const double ConeApexZ = 9.5;

 

            //Vector3D: Cone, TriangleFan With 36 Vertices

 

            IGeometryCollection multiPatchGeometryCollection = new MultiPatchClass();

 

            IPointCollection triangleFanPointCollection = new TriangleFanClass();

 

            //Set Cone Apex To (0, 0, ConeApexZ)

 

            IPoint coneApexPoint = ConstructPoint3D(0, 0, ConeApexZ);

 

            //Add Cone Apex To Triangle Fan

 

            triangleFanPointCollection.AddPoint(coneApexPoint, ref _missing, ref _missing);

 

            //Define Upper Portion Of Axis Around Which Vector Should Be Rotated To Generate Cone Base Vertices

 

            IVector3D upperAxisVector3D = ConstructVector3D(0, 0, 10);

 

            //Define Lower Portion of Axis Around Which Vector Should Be Rotated To Generate Cone Base Vertices

 

            IVector3D lowerAxisVector3D = ConstructVector3D(0, 0, -10);

 

            //Add A Slight Offset To X or Y Component Of One Of Axis Vectors So Cross Product Does Not Return A Zero-Length Vector

 

            lowerAxisVector3D.XComponent += VectorComponentOffset;

 

            //Obtain Cross Product Of Upper And Lower Axis Vectors To Obtain Normal Vector To Axis Of Rotation To Generate Cone Base Vertices

 

            IVector3D normalVector3D = upperAxisVector3D.CrossProduct(lowerAxisVector3D) as IVector3D;

 

            //Set Normal Vector Magnitude Equal To Radius Of Cone Base

 

            normalVector3D.Magnitude = ConeBaseRadius;

 

            //Obtain Angle Of Rotation In Radians As Function Of Number Of Divisions Within 360 Degree Sweep Of Cone Base

 

            double rotationAngleInRadians = GetRadians(ConeBaseDegrees / ConeBaseDivisions);

 

            for (int i = 0; i < ConeBaseDivisions; i++)

            {

                //Rotate Normal Vector Specified Rotation Angle In Radians Around Either Upper Or Lower Axis

 

                normalVector3D.Rotate(-1 * rotationAngleInRadians, upperAxisVector3D);

 

                //Construct Cone Base Vertex Whose XY Coordinates Are The Sum Of Apex XY Coordinates And Normal Vector XY Components

 

                IPoint vertexPoint = ConstructPoint3D(coneApexPoint.X + normalVector3D.XComponent,

                                                      coneApexPoint.Y + normalVector3D.YComponent,

                                                      ConeBaseZ);

 

                //Add Vertex To TriangleFan

 

                triangleFanPointCollection.AddPoint(vertexPoint, ref _missing, ref _missing);

            }

 

            //Re-Add The Second Point Of The Triangle Fan (First Vertex Added) To Close The Fan

 

            triangleFanPointCollection.AddPoint(triangleFanPointCollection.get_Point(1), ref _missing, ref _missing);

 

            //Add TriangleFan To MultiPatch

 

            multiPatchGeometryCollection.AddGeometry(triangleFanPointCollection as IGeometry, ref _missing, ref _missing);

 

            return multiPatchGeometryCollection as IGeometry;

        }

 

        private static IPoint ConstructPoint3D(double x, double y, double z)

        {

            IPoint point = ConstructPoint2D(x, y);

            point.Z = z;

            return point;

        }

        private static IPoint ConstructPoint2D(double x, double y)

        {

            IPoint point = new PointClass();

            point.PutCoords(x, y);
 

            return point;

        }

        private static double GetRadians(double decimalDegrees)

        {

            return decimalDegrees * (Math.PI / 180);

        }