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using System;
using OpenSim.Region.Environment.Interfaces;
namespace OpenSim.Region.Environment.Modules.Terrain
{
public static class TerrainUtil
{
public static double MetersToSphericalStrength(double size)
{
return Math.Pow(2, size);
}
public static double SphericalFactor(double x, double y, double rx, double ry, double size)
{
return size * size - ((x - rx) * (x - rx) + (y - ry) * (y - ry));
}
public static double GetBilinearInterpolate(double x, double y, ITerrainChannel map)
{
int w = map.Width;
int h = map.Height;
if (x > w - 2.0)
x = w - 2.0;
if (y > h - 2.0)
y = h - 2.0;
if (x < 0.0)
x = 0.0;
if (y < 0.0)
y = 0.0;
int stepSize = 1;
double h00 = map[(int)x, (int)y];
double h10 = map[(int)x + stepSize, (int)y];
double h01 = map[(int)x, (int)y + stepSize];
double h11 = map[(int)x + stepSize, (int)y + stepSize];
double h1 = h00;
double h2 = h10;
double h3 = h01;
double h4 = h11;
double a00 = h1;
double a10 = h2 - h1;
double a01 = h3 - h1;
double a11 = h1 - h2 - h3 + h4;
double partialx = x - (int)x;
double partialz = y - (int)y;
double hi = a00 + (a10 * partialx) + (a01 * partialz) + (a11 * partialx * partialz);
return hi;
}
private static double Noise(double x, double y)
{
int n = (int)x + (int)(y * 749);
n = (n << 13) ^ n;
return (1.0 - ((n * (n * n * 15731 + 789221) + 1376312589) & 0x7fffffff) / 1073741824.0);
}
private static double SmoothedNoise1(double x, double y)
{
double corners = (Noise(x - 1, y - 1) + Noise(x + 1, y - 1) + Noise(x - 1, y + 1) + Noise(x + 1, y + 1)) / 16;
double sides = (Noise(x - 1, y) + Noise(x + 1, y) + Noise(x, y - 1) + Noise(x, y + 1)) / 8;
double center = Noise(x, y) / 4;
return corners + sides + center;
}
private static double Interpolate(double x, double y, double z)
{
return (x * (1.0 - z)) + (y * z);
}
private static double InterpolatedNoise(double x, double y)
{
int integer_X = (int)(x);
double fractional_X = x - integer_X;
int integer_Y = (int)y;
double fractional_Y = y - integer_Y;
double v1 = SmoothedNoise1(integer_X, integer_Y);
double v2 = SmoothedNoise1(integer_X + 1, integer_Y);
double v3 = SmoothedNoise1(integer_X, integer_Y + 1);
double v4 = SmoothedNoise1(integer_X + 1, integer_Y + 1);
double i1 = Interpolate(v1, v2, fractional_X);
double i2 = Interpolate(v3, v4, fractional_X);
return Interpolate(i1, i2, fractional_Y);
}
public static double PerlinNoise2D(double x, double y, int octaves, double persistence)
{
double frequency = 0.0;
double amplitude = 0.0;
double total = 0.0;
for (int i = 0; i < octaves; i++)
{
frequency = System.Math.Pow(2, i);
amplitude = System.Math.Pow(persistence, i);
total += InterpolatedNoise(x * frequency, y * frequency) * amplitude;
}
return total;
}
}
}
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