//得到箭头
public static IGeometry GetArrow()
{
const double ConeBaseDegrees = 360.0;
const int ConeBaseDivisions = 36;
const double VectorComponentOffset = 0.0000001;
const double ConeBaseZ = 0.0;
double ConeApexZ = 0;
double ConeBaseRadius = 0;
ConeBaseRadius = 20; //范围 //正常
ConeApexZ = 100; //尖度
//Vector3D: Cone, TriangleFan With 36 Vertices
IGeometryCollection multiPatchGeometryCollection = new MultiPatchClass();
IPointCollection triangleFanPointCollection = new TriangleFanClass();
//Set Cone Apex To (0, 0, ConeApexZ)
IPoint coneApexPoint = GeometryUtilities.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 = GeometryUtilities.ConstructVector3D(0, 0, 10);
//Define Lower Portion of Axis Around Which Vector Should Be Rotated To Generate Cone Base Vertices
IVector3D lowerAxisVector3D = GeometryUtilities.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 = GeometryUtilities.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 = GeometryUtilities.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);
}
