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104 lines
3.0 KiB
C#
104 lines
3.0 KiB
C#
// Source from http://mrl.nyu.edu/~perlin/noise/
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// Optimised form as we can always treat Z as being = 0.
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// Octave and combined noise based on:
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// https://github.com/UnknownShadow200/ClassicalSharp/wiki/Minecraft-Classic-map-generation-algorithm
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using System;
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namespace ClassicalSharp.Generator {
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public abstract class Noise {
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public abstract double Compute( double x, double y );
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}
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public sealed class ImprovedNoise : Noise {
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public ImprovedNoise( Random rnd ) {
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// make a random initial permutation based on seed,
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// instead of using fixed permutation table in original code.
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for( int i = 0; i < 256; i++ )
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p[i + 256] = p[i] = rnd.Next( 256 );
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}
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// TODO: need to half this maybe?
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public override double Compute( double x, double y ) {
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int xFloor = Utils.Floor( x ), yFloor = Utils.Floor( y );
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// Find unit rectangle that contains point
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int X = xFloor & 0xFF, Y = yFloor & 0xFF;
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// Find relative x, y of each point in rectangle.
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x -= Math.Floor( x ); y -= Math.Floor( y );
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// Compute fade curves for each of x, y.
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double u = Fade( x ), v = Fade( y );
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// Hash coordinates of the 4 rectangle corners.
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int A = p[X] + Y, AA = p[A], AB = p[A + 1],
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B = p[X + 1] + Y, BA = p[B], BB = p[B + 1];
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// and add blended results from 4 corners of rectangle.
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return Lerp(
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v,
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Lerp( u, Grad( p[AA], x, y ),
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Grad( p[BA], x - 1, y ) ),
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Lerp( u, Grad( p[AB], x, y - 1 ),
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Grad( p[BB], x - 1, y - 1 ) )
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);
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}
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static double Fade( double t ) {
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return t * t * t * (t * (t * 6 - 15) + 10);
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}
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static double Lerp( double t, double a, double b ) {
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return a + t * (b - a);
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}
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static double Grad( int hash, double x, double y ) {
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// convert low 4 bits of hash code into 12 gradient directions.
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int h = hash & 15;
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double u = h < 8 ? x : y;
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double v = h < 4 ? y : h == 12 || h == 14 ? x : 0;
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return ((h & 1) == 0 ? u : -u) + ((h & 2) == 0 ? v : -v);
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}
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int[] p = new int[512];
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}
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public sealed class OctaveNoise : Noise {
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readonly int octaves;
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readonly ImprovedNoise[] baseNoise;
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public OctaveNoise( int octaves, Random rnd ) {
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this.octaves = octaves;
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baseNoise = new ImprovedNoise[octaves];
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for( int i = 0; i < octaves; i++ )
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baseNoise[i] = new ImprovedNoise( rnd );
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}
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public override double Compute( double x, double y ) {
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double amplitude = 1, frequency = 1;
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double sum = 0;
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for( int i = 0; i < baseNoise.Length; i++ ) {
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sum += baseNoise[i].Compute( x * frequency, y * frequency ) * amplitude;
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amplitude *= 2;
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frequency /= 2;
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}
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return sum;
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}
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}
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public sealed class CombinedNoise : Noise {
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readonly Noise noise1, noise2;
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public CombinedNoise( Noise noise1, Noise noise2 ) {
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this.noise1 = noise1;
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this.noise2 = noise2;
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}
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public override double Compute( double x, double y ) {
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double offset = noise2.Compute( x, y );
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return noise1.Compute( x + offset, y );
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}
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}
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}
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