//精确角度绘制副区
public List <Point3D> DrawAccruateOffset(double offSet = 0, double step = 1)
{
//绘制指定θ角范围的风螺旋线，所有参数均为 弧度数。
double sita = startSita;
Point3D p1 = GetTangentPoint(startSita);
Point3D p2 = p1.Add(WindSpirlTool.Polar(offSet, startSita - _DA));
//建立点串
List <Point3D> points = new List <Point3D>();
points.Add(p2);
Point3D OffsetStartPoint = new Point3D();
OffsetStartPoint.X = p2.X;
OffsetStartPoint.Y = p2.Y;
while (sita < endSita)
{
sita += step * Math.PI / 180;
p1 = GetTangentPoint(sita);
p2 = p1.Add(WindSpirlTool.Polar(offSet, sita - _DA));
points.Add(p2);
}
p1 = GetTangentPoint(endSita);
Point3D OffsetEndPoint = new Point3D();
OffsetEndPoint = p1.Add(WindSpirlTool.Polar(offSet, endSita - _DA));
points.Add(OffsetEndPoint);
return(points);
}
//根据线外点 pointB，求过该点的风螺旋线切线的切点所对应的 sita 角
public double GetTangentSita(Point3D pointB)
{
//输入风螺旋线外点，求过该点的切线对应的sita角度（单位：弧度）
//圆心点C，线外点B，圆弧上的切点A，螺旋线上的切点D
Point3D pointC = new Point3D(0, 0);//圆心默认位置
double dist = WindSpirlTool.Distance(pointB, pointC);
//atan2 函数具有指向性，但常出现负值，需要转换处理。
double alfa = Math.Atan2(pointB.Y - pointC.Y, pointB.X - pointC.X);
alfa = (alfa + 2 * Math.PI) % (2 * Math.PI);//转换成正值
double beta = Math.Acos((_r / dist));
double sita = alfa - beta;
//check distance of B is out of the windspiral
//用 getSpiralPoint 函数来检测
Point3D tempPt = GetTangentPoint(GetSita(alfa));
if (dist < WindSpirlTool.Distance(tempPt, pointC))
{
throw new Exception("The distance of L is too short. Please enlarge the outbound time.");
}
//the tangent point of Norminal Track
Point3D p = WindSpirlTool.Polar(_r, sita);
Point3D pointA = pointC.Add(p); //add
//the initial tangent point of Wind Spiral
p = WindSpirlTool.Polar((_esita * sita), sita - _DA);
Point3D pointD = pointA.Add(p); //add
double calcuSita = Math.Atan2(pointB.Y - pointD.Y, pointB.X - pointD.X);
calcuSita = (calcuSita + 2 * Math.PI) % (2 * Math.PI);//转换成正值
double tolerance = calcuSita - ((sita - _DA) + Math.PI / 2);
double j = 0;
while (tolerance > 0.0000001)
{
sita += tolerance;
p = WindSpirlTool.Polar(_r, sita);
pointA = pointC.Add(p); //add
p = WindSpirlTool.Polar((_esita * sita), sita - _DA);
pointD = pointA.Add(p); //add
calcuSita = Math.Atan2(pointB.Y - pointD.Y, pointB.X - pointD.X);
calcuSita = (calcuSita + 2 * Math.PI) % (2 * Math.PI);//转换成正值
tolerance = calcuSita - sita + _DA - Math.PI / 2;
//trace( newMinus );
j += 1;
}
return(sita);
}