public void PlotSurface(double x1, double y1, double x2, double y2, double fmin, double fmax, int n1, int n2, int Dx, int Dy, Graphics g)
        {
            Point[] CurLine = new Point[n1];
            double phi = Phi * Math.PI / 180;
            double psi = Psi * Math.PI / 180;
            double sphi = Math.Sin(phi);
            double spsi = Math.Sin(psi);
            double cphi = Math.Cos(phi);
            double cpsi = Math.Cos(psi);
            double[] e1 = new double[3] { cphi, sphi, 0 };
            double[] e2 = new double[3] { spsi * sphi, -spsi * cphi, cpsi };
            double x, y;
            double hx = (x2 - x1) / n1;
            double hy = (y2 - y1) / n2;
            double xmin = (e1[0] >= 0 ? x1 : x2) * e1[0] +
             (e1[1] >= 0 ? y1 : y2) * e1[1];
            double xmax = (e1[0] >= 0 ? x2 : x1) * e1[0] +
             (e1[1] >= 0 ? y2 : y1) * e1[1];
            double ymin = (e2[0] >= 0 ? x1 : x2) * e2[0] +
             (e2[1] >= 0 ? y1 : y2) * e2[1];
            double ymax = (e2[0] >= 0 ? x2 : x1) * e2[0] +
             (e2[1] >= 0 ? y2 : y1) * e2[1];
            int i, j;
            if (e2[2] >= 0)
            {
                ymin += fmin * e2[2];
                ymax += fmax * e2[2];
            }
            else
            {
                ymin += fmax * e2[2];
                ymax += fmin * e2[2];
            }
            double ax = Dx - (MAXX - 40) * xmin / (xmax - xmin);
            double bx = (MAXX - 40) / (xmax - xmin);
            double ay = Dy - (MAXY - 80) * ymin / (ymax - ymin);
            double by = -(MAXY - 80) / (ymax - ymin);
            for (i = 0; i < MAXX; i++)
                YMin[i] = YMax[i] = 0;
            for (i = n2 - 1; i > -1; i--)
            {
                for (j = 0; j < n1; j++)
                {
                    x = x1 + j * hx;
                    y = y1 + i * hy;
                    CurLine[j].X = (int)(ax + bx * (x * e1[0] + y * e1[1]));
                    CurLine[j].Y = (int)(ay + by * (x * e2[0] + y * e2[1] +
                      f(x, y) * e2[2]));
                }
                for (j = 0; j < n1 - 1; j++)
                    DrawLine(CurLine[j], CurLine[j + 1], g);
                    ///g.DrawLine(new Pen(Color.Black), CurLine[j], CurLine[j + 1]);
            }
        }