1.圆弧倒角

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  1.                          DVector2d vS = vecStart;
  2.             DVector2d vE = vecEnd;
  3.             if (vS.IsParallelTo(vE)) return ;
  5.             vS.NormalizeInPlace();
  6.             vE.NormalizeInPlace();
  8.             DVector2d vMid = vS + vE;
  9.             vMid.NormalizeInPlace();
  11.             Angle halfAngel = vS.AngleTo(vMid);
  13.             double sDis = R / Math.Tan(halfAngel.Radians);
  14.             double cDis = R / Math.Sin(halfAngel.Radians);
  16.             DVector2d ptCenter   = ptInter + cDis * vMid;
  17.             DVector2d ptArcStart = ptInter + sDis * vS;
  18.             DVector2d ptArcEnd   = ptInter + sDis * vE;

2.不规则倒角计算

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In:ptInter,vecStart,vecEnd,vecHaunch
Out:ptStart,ptEnd
只要保证三个矢量方向正确就可以了
vecHaunch一定是从VecStart指向VecEnd
在函数构建好VecHaunch，这样就可以适用于各种方向了，如上图

                        if (vecStart.IsParallelTo(vecEnd))
                return ;

            double angInter = vecStart.AngleTo(vecEnd).Radians;
            double angStart = Angle.PI.Radians - vecStart.AngleTo(vecHaunch).Radians;
            double angEnd   = vecEnd.AngleTo(vecHaunch).Radians;
            //     已知，角A,B,C, 边a,求：b,c
            //     根据公式：
            //     a/sinA = b/sinB = c/sinC
            //     b = a(sinB/sinA)
            //     c = a(sinC/sinA)

            vecStart.NormalizeInPlace();
            vecEnd.NormalizeInPlace();

            double leng = vecHaunch.MagnitudeXY;
            double lStart = Math.Sin(angEnd) * leng / Math.Sin(angInter);
            double lEnd = Math.Sin(angStart) * leng / Math.Sin(angInter);

            DVector2d ptStart = ptInter + lStart * vecStart;
            DVector2d ptEnd = ptInter + lEnd * vecEnd;