static public bool GetArcByPoint(GE_Point pt1, GE_Point pt2, GE_Point pt3, out GE_Point ptCenter)
{
bool bRet = false;
ptCenter = new GE_Point();
GE_Line lin1 = new GE_Line();
GE_Line lin2 = new GE_Line();
GE_Point ptM1 = Geo.AcGeMidPoint(pt1, pt2);
GE_Point ptM2 = Geo.AcGeMidPoint(pt2, pt3);
GE_Vector vp = Geo.GetVector(pt1, pt2);
vp.RotateBy(PI2);
lin1.set(ptM1, ptM1 + vp * 100.0);
vp = Geo.GetVector(pt2, pt3);
vp.RotateBy(PI2);
lin2.set(ptM2, ptM2 + vp * 100.0);
GE_Point ptCen1, ptCen2;
int nRet = lin1.intersectWith(lin2, out ptCen1, out ptCen2);
if (nRet > 0)
{
ptCenter = ptCen1;
bRet = true;
}
return(bRet);
}
/// <summary>
///
/// </summary>
/// <param name="lin"></param>
/// <param name="ptInt1"></param>
/// <param name="ptInt2"></param>
/// <returns></returns>
public int intersectWith(GE_Line lin, out GE_Point ptInt1, out GE_Point ptInt2)
{
int nRet = 0;
ptInt1 = new GE_Point(0, 0);
ptInt2 = new GE_Point(0, 0);
double A, B, a, b, c, d, P, Q, AA, BB, CC, X1, X2, Y1, Y2;
double u;
if (m_Kind == 0 && lin.m_Kind == 0)
{
PointF point1 = new PointF((float)m_StartPoint.X, (float)m_StartPoint.Y);
PointF point2 = new PointF((float)m_EndPoint.X, (float)m_EndPoint.Y);
PointF point3 = new PointF((float)lin.m_StartPoint.X, (float)lin.m_StartPoint.Y);
PointF point4 = new PointF((float)lin.m_EndPoint.X, (float)lin.m_EndPoint.Y);
PointF pointResult;
if (GetIntersection(point1, point2, point3, point4, out pointResult))
{
ptInt1.X = pointResult.X;
ptInt1.Y = pointResult.Y;
nRet = 1;
}
//double x11, y11, x12, y12, x21, y21, x22, y22;
//x11 = m_StartPoint.X;
//y11 = m_StartPoint.Y;
//x12 = m_EndPoint.X;
//y12 = m_EndPoint.Y;
//x21 = lin.m_StartPoint.X;
//y21 = lin.m_StartPoint.Y;
//x22 = lin.m_EndPoint.X;
//y22 = lin.m_EndPoint.Y;
//u = (x11 - x21) / ((x22 - x21) - (x12 - x11));
//ptInt1.X = x11 + u * (x12 - x11);
//ptInt1.Y = y11 + u * (y12 - y11);
//nRet = 1;
}
else if (m_Kind == 1 && lin.m_Kind == 1)
{
A = m_CenterPoint.distanceTo(m_StartPoint);
B = lin.m_CenterPoint.distanceTo(lin.m_StartPoint);
a = m_CenterPoint.X;
b = m_CenterPoint.Y;
c = lin.m_CenterPoint.X;
d = lin.m_CenterPoint.Y;
P = ((A * A - B * B) - (a * a + b * b - c * c - d * d)) / (2 * d - 2 * b);
Q = (c - a) / (d - b);
AA = 1 + Q * Q;
BB = 2 * b * Q - 2 * P * Q - 2 * a;
CC = P * P - 2 * b * P - A * A + a * a + b * b;
if (BB * BB - 4 * AA * CC > 0)
{
X1 = (BB * -1 + Math.Sqrt(BB * BB - 4 * AA * CC)) / (2 * AA);
X2 = (BB * -1 - Math.Sqrt(BB * BB - 4 * AA * CC)) / (2 * AA);
Y1 = P - Q * X1;
Y2 = P - Q * X2;
ptInt1.X = X1; ptInt1.Y = Y1;
ptInt2.X = X2; ptInt2.Y = Y2;
nRet = 2;
}
else
{
nRet = 0;
}
}
return(nRet);
}
