, Visual C#


- 2


private void FindPointOnCurve(ref float x, ref float y,

float LevelCurves, float start_x, float start_y,

float tolerance)

{

float dx = 0, dy = 0, dz, delta, f_xy;

int direction = 0;

// :

x = start_x; y = start_y; delta = initial_delta;

// do-while break:

int i = 0;

do

{

f_xy = f(x, y); dz = LevelCurves - f_xy;

if (Math.Abs(dz) < tolerance) break;

// :

if (Math.Sign(dz) != direction)

{

// . delta:

delta = delta / 2;

direction = Math.Sign(dz);

}

// :

Gradient(x, y, ref dx, ref dy);

if ((Math.Abs(dx) + Math.Abs(dy)) < 0.001) break;

// :

x = x + dx * delta * (float)direction;

y = y + dy * delta * (float)direction;

}

while (i < 1);

}

// :

private void Gradient(float x, float y,

ref float dx, ref float dy)

{

float dist = 0;

dx = df_dx(x, y); dy = df_dy(x, y);

dist = Convert.ToSingle(Math.Sqrt(dx * dx + dy * dy));

if (Math.Abs(dist) < 0.0001)

{

dx = 0; dy = 0;

}

else

{

dx = dx / dist; dy = dy / dist;

}

}

// f(x, y) = LevelCurves:

private void PlotLevelCurve(Graphics g,

float LevelCurves, float x_min, float x_max, float y_min,

float y_max, float step_size,

float start_x, float start_y,

float tolerance)

{

int num_points = 0;

float x0 = 0, y0 = 0, x1, y1, x2, y2, dx = 0, dy = 0;

// (x0, y0) LevelCurves:

FindPointOnCurve(ref x0, ref y0, LevelCurves,

start_x, start_y, tolerance);

//:

num_points = 1;