/// <summary>
/// Calculates the height of the specified midpoint against its Von Neumann neighborhood.
/// </summary>
/// <param name="t">Playground.</param>
/// <param name="M">Midpoint in question.</param>
/// <param name="SS">Section step.</param>
/// <returns>Transformed midpoint.</returns>
private static double GetMidpointHeight(Terrain t, HeightPoint M, int SS)
{
// T
// L M R
// B
HeightPoint L, R, T, B;
int size;
// No error checking here bacuse it is called from an inner loop.
size = t.Size.Width;
L = M + (HeightPoint.LeftVector * SS / 2);
R = M + (HeightPoint.RightVector * SS / 2);
T = M + (HeightPoint.TopVector * SS / 2);
B = M + (HeightPoint.BottomVector * SS / 2);
if (L.X < 0)
{
L.X = size - 1;
}
if (R.X >= size)
{
R.X = 0;
}
if (T.Y < 0)
{
T.Y = size - 1;
}
if (B.Y >= size)
{
B.Y = 0;
}
L.Height = t[L.X, L.Y];
R.Height = t[R.X, R.Y];
T.Height = t[T.X, T.Y];
B.Height = t[B.X, B.Y];
M = HeightPoint.Midpoint(L, R, T, B);
return(M.Height);
}
/// <summary>
/// Strict, iterative implementation of the Diamond-Square terrain generation algorithm.
/// Terrain must be a square with edges in the form of 2^I + 1, where I is the number of required iteraions.
/// </summary>
/// <param name="t">Terrain to use.</param>
/// <param name="H">Jag parameter.</param>
public static void DiamondSquare_Strict(Terrain t, [AttributeDouble("Jag Parameter", 1.0, 0.0, 10.0, 2, 0.1)] double H)
{
// A e B e:AB f:AC g:BD h:CD
// f M g M:AD
// C h D
VerifyNotNull(t, "t");
VerifyValidDouble(H, "H");
if (t.Size.Width != t.Size.Height)
{
throw new ArgumentException("Terrain height and width must be equal.", "t");
}
if (Math.Log(t.Size.Width - 1, 2) != (int)Math.Log(t.Size.Width - 1, 2))
{
throw new ArgumentException("Terrain size must be in the form of 2^I + 1.", "t");
}
HeightPoint A, B, C, D;
HeightPoint M, e, f, g, h;
int size;
int SP, I, SC, SS, Sx, Sy;
double R, r;
Random rg;
// Get terrain size, initialize RNG and randomize the four terrain corners.
size = t.Size.Width;
rg = new Random();
r = 0; // GetRandom(rg, 1);
t[0, 0] = r;
t[size - 1, 0] = r;
t[0, size - 1] = r;
t[size - 1, size - 1] = r;
#region REPORT INIT
if (t.PBW != null)
{
t.PBW.Report("Diamond Square (Strict)", (int)((2.0 / 3.0) * (double)(size * size - 2 * size)));
if (t.PBW.CancellationPending)
{
return;
}
}
#endregion
SP = (int)Math.Log(size - 1, 2);
for (I = 0; I < SP; I++)
{
SS = (int)Math.Pow(2, SP - I);
SC = (int)Math.Pow(2, I);
R = Math.Pow(2, (-H * I));
// Diamond step
for (Sx = 0; Sx < SC; Sx++)
{
for (Sy = 0; Sy < SC; Sy++)
{
#region REPORT
if (t.PBW != null)
{
t.PBW.Report();
if (t.PBW.CancellationPending)
{
return;
}
}
#endregion
// Find the four corners and thier heights.
A = new HeightPoint(SS * Sx, SS * Sy);
B = new HeightPoint(SS * (Sx + 1), SS * Sy);
C = new HeightPoint(SS * Sx, SS * (Sy + 1));
D = new HeightPoint(SS * (Sx + 1), SS * (Sy + 1));
A.Height = t[A.X, A.Y];
B.Height = t[B.X, B.Y];
C.Height = t[C.X, C.Y];
D.Height = t[D.X, D.Y];
// Find the center and calculate its height.
M = A % D;
r = GetRandom(rg, R);
M.Height = (A.Height + B.Height + C.Height + D.Height) / 4 + r;
// Store the results.
t[M.X, M.Y] = M.Height;
}
}
// Square step
for (Sx = 0; Sx < SC; Sx++)
{
for (Sy = 0; Sy < SC; Sy++)
{
#region REPORT
if (t.PBW != null)
{
t.PBW.Report();
if (t.PBW.CancellationPending)
{
return;
}
}
#endregion
// Find the four corners and their heights.
A = new HeightPoint(SS * Sx, SS * Sy);
B = new HeightPoint(SS * (Sx + 1), SS * Sy);
C = new HeightPoint(SS * Sx, SS * (Sy + 1));
D = new HeightPoint(SS * (Sx + 1), SS * (Sy + 1));
// For each midpoint, find its coordinates, calculate height and store the result.
e = A % B;
e.Height = GetMidpointHeight(t, e, SS);
t[e.X, e.Y] = e.Height;
f = A % C;
f.Height = GetMidpointHeight(t, f, SS);
t[f.X, f.Y] = f.Height;
if (Sx == (SC - 1))
{
g = B % D;
g.Height = GetMidpointHeight(t, g, SS);
t[g.X, g.Y] = g.Height;
}
if (Sy == (SC - 1))
{
h = C % D;
h.Height = GetMidpointHeight(t, h, SS);
t[h.X, h.Y] = h.Height;
}
}
}
}
t.Normalize();
}
