/// <summary>
/// 判断两条线段是否相交。
/// </summary>
/// <param name="line1">线段1</param>
/// <param name="line2">线段2</param>
/// <returns>相交返回真，否则返回假。</returns>
public static bool CheckTwoLineCrose(LineD line1, LineD line2)
{
return(CheckCrose(line1, line2) && CheckCrose(line2, line1));
}
/**************************************求交***************************************************/
/// <summary>
/// 两直线求交,返回交点 线公式 AX+BY+C1=0;
/// </summary>
/// <param name="lineA_z"></param>
/// <param name="lineB"></param>
/// <returns></returns>
public static Point jiaoD(this LineD lineA_z, LineD lineB)
{
//定义交点
Point res = new Point();
double X1 = 0, X2 = 0, X3 = 0, X4 = 0, Y1 = 0, Y2 = 0, Y3 = 0, Y4 = 0;
if (Math.Abs(lineA_z.Start.X - lineA_z.End.X) > 0.01)
{
//lineA的两点坐标
X1 = lineA_z.Start.X;
Y1 = lineA_z.Start.Y;
X2 = lineA_z.End.X;
Y2 = lineA_z.End.Y;
//lineB的两点坐标
X3 = lineB.Start.X;
Y3 = lineB.Start.Y;
X4 = lineB.End.X;
Y4 = lineB.End.Y;
}
else if (Math.Abs(lineB.Start.X - lineB.End.X) > 0.01)
{
//lineB的两点坐标
X1 = lineB.Start.X;
Y1 = lineB.Start.Y;
X2 = lineB.End.X;
Y2 = lineB.End.Y;
//lineA的两点坐标
X3 = lineA_z.Start.X;
Y3 = lineA_z.Start.Y;
X4 = lineA_z.End.X;
Y4 = lineA_z.End.Y;
}
else
{
MessageBox.Show("求交过程中被输入两条平行线,无法获得交点");
}
//lineA套入直线公式
double A1 = Y2 - Y1;
double B1 = X1 - X2;
double C1 = X2 * Y1 - X1 * Y2;
//lineB套入直线公式
double A2 = Y4 - Y3;
double B2 = X3 - X4;
double C2 = X4 * Y3 - X3 * Y4;
//A1*X+B1*Y+C1=0;
//A2*X+B2*Y+C2=0;
///y=a0+a1*x
///a1*x-y+a0=0
///A=a1
///B=-1
///
//解出交点
// 1 提出lineA中的未知数Y
// Y*B1 = -A1*X - C1;
// Y = -X*A1/B1 - C1/B1;
// 2 把Y 套入 lineB的公式中
// A2*X+B2*(-A1/B1 * X - C1/B1)+C2=0;
// 3 提出lineB的公式中的未知数X
// A2*X + B2*(-X*A1/B1 - C1/B1) + C2=0;
// double g =B2*(A1/B1);
// double h =B2*(C1/B1);
// A2*X + (-B2*(A1/B1) * X - B2*(C1/B1)) + C2=0;
// A2*X + (-g * X - h) + C2=0;
// A2*X - g * X =h-C2;
// (A2-g)*X=h-C2;
// X=(h-C2)/(A2-g);
res.X = (B2 * (C1 / B1) - C2) / (A2 - B2 * (A1 / B1));
//4 把X套入步骤 1的公式
res.Y = -res.X * A1 / B1 - C1 / B1;
res.Z = lineA_z.Start.Z;
return(res);
}
