SimplexNoise.java

/*
 * A speed-improved simplex noise algorithm for 2D, 3D and 4D in Java.
 *
 * Based on example code by Stefan Gustavson (stegu@itn.liu.se).
 * Optimisations by Peter Eastman (peastman@drizzle.stanford.edu).
 * Better rank ordering method for 4D by Stefan Gustavson in 2012.
 *
 * This could be speeded up even further, but it's useful as it is.
 *
 * Version 2012-03-09
 *
 * This code was placed in the public domain by its original author,
 * Stefan Gustavson. You may use it as you see fit, but
 * attribution is appreciated.
 *
 */

public class SimplexNoise 
{ // Simplex noise in 2D, 3D and 4D

    //class is just for fun and will likely not be in the final version. 

    private static Grad grad3[] = 
    { 
        new Grad(1, 1, 0), new Grad(-1, 1, 0), new Grad(1, -1, 0), new Grad(-1, -1, 0),
        new Grad(1, 0, 1), new Grad(-1, 0, 1), new Grad(1, 0, -1), new Grad(-1, 0, -1),
        new Grad(0, 1, 1), new Grad(0, -1, 1), new Grad(0, 1, -1), new Grad(0, -1, -1) 
    };

    private static short p[] = 
    {
        151, 160, 137, 91, 90, 15,
        131, 13, 201, 95, 96, 53, 194, 233, 7, 225, 140, 36, 103, 30, 69, 142, 8, 99, 37, 240, 21, 10, 23,
        190, 6, 148, 247, 120, 234, 75, 0, 26, 197, 62, 94, 252, 219, 203, 117, 35, 11, 32, 57, 177, 33,
        88, 237, 149, 56, 87, 174, 20, 125, 136, 171, 168, 68, 175, 74, 165, 71, 134, 139, 48, 27, 166,
        77, 146, 158, 231, 83, 111, 229, 122, 60, 211, 133, 230, 220, 105, 92, 41, 55, 46, 245, 40, 244,
        102, 143, 54, 65, 25, 63, 161, 1, 216, 80, 73, 209, 76, 132, 187, 208, 89, 18, 169, 200, 196,
        135, 130, 116, 188, 159, 86, 164, 100, 109, 198, 173, 186, 3, 64, 52, 217, 226, 250, 124, 123,
        5, 202, 38, 147, 118, 126, 255, 82, 85, 212, 207, 206, 59, 227, 47, 16, 58, 17, 182, 189, 28, 42,
        223, 183, 170, 213, 119, 248, 152, 2, 44, 154, 163, 70, 221, 153, 101, 155, 167, 43, 172, 9,
        129, 22, 39, 253, 19, 98, 108, 110, 79, 113, 224, 232, 178, 185, 112, 104, 218, 246, 97, 228,
        251, 34, 242, 193, 238, 210, 144, 12, 191, 179, 162, 241, 81, 51, 145, 235, 249, 14, 239, 107,
        49, 192, 214, 31, 181, 199, 106, 157, 184, 84, 204, 176, 115, 121, 50, 45, 127, 4, 150, 254,
        138, 236, 205, 93, 222, 114, 67, 29, 24, 72, 243, 141, 128, 195, 78, 66, 215, 61, 156, 180 
    };

    // To remove the need for index wrapping, double the permutation table length
    private static short perm[] = new short[512];
    private static short permMod12[] = new short[512];
    static {
        for (int i = 0; i < 512; i++) {
            perm[i] = p[i & 255];
            permMod12[i] = (short) (perm[i] % 12);
        }
    }

    // Skewing and unskewing factors for 2, 3, and 4 dimensions
    private static final double F2 = 0.5 * (Math.sqrt(3.0) - 1.0);
    private static final double G2 = (3.0 - Math.sqrt(3.0)) / 6.0;

    // This method is a *lot* faster than using (int)Math.floor(x)
    private static int fastfloor(double x) 
    {
        int xi = (int) x;
        return x < xi ? xi - 1 : xi;
    }

    private static double dot(Grad g, double x, double y) 
    {
        return g.x * x + g.y * y;
    }

    // 2D simplex noise
    public static double noise(double xin, double yin) 
    {
        double n0, n1, n2; // Noise contributions from the three corners
        // Skew the input space to determine which simplex cell we're in
        double s = (xin + yin) * F2; // Hairy factor for 2D
        int i = fastfloor(xin + s);
        int j = fastfloor(yin + s);
        double t = (i + j) * G2;
        double X0 = i - t; // Unskew the cell origin back to (x,y) space
        double Y0 = j - t;
        double x0 = xin - X0; // The x,y distances from the cell origin
        double y0 = yin - Y0;
        // For the 2D case, the simplex shape is an equilateral triangle.
        // Determine which simplex we are in.
        int i1, j1; // Offsets for second (middle) corner of simplex in (i,j) coords
        if (x0 > y0) {
            i1 = 1;
            j1 = 0;
        } // lower triangle, XY order: (0,0)->(1,0)->(1,1)
        else {
            i1 = 0;
            j1 = 1;
        } // upper triangle, YX order: (0,0)->(0,1)->(1,1)
        // A step of (1,0) in (i,j) means a step of (1-c,-c) in (x,y), and
        // a step of (0,1) in (i,j) means a step of (-c,1-c) in (x,y), where
        // c = (3-sqrt(3))/6
        double x1 = x0 - i1 + G2; // Offsets for middle corner in (x,y) unskewed coords
        double y1 = y0 - j1 + G2;
        double x2 = x0 - 1.0 + 2.0 * G2; // Offsets for last corner in (x,y) unskewed coords
        double y2 = y0 - 1.0 + 2.0 * G2;
        // Work out the hashed gradient indices of the three simplex corners
        int ii = i & 255;
        int jj = j & 255;
        int gi0 = permMod12[ii + perm[jj]];
        int gi1 = permMod12[ii + i1 + perm[jj + j1]];
        int gi2 = permMod12[ii + 1 + perm[jj + 1]];
        // Calculate the contribution from the three corners
        double t0 = 0.5 - x0 * x0 - y0 * y0;
        if (t0 < 0)
            n0 = 0.0;
        else {
            t0 *= t0;
            n0 = t0 * t0 * dot(grad3[gi0], x0, y0); // (x,y) of grad3 used for 2D gradient
        }
        double t1 = 0.5 - x1 * x1 - y1 * y1;
        if (t1 < 0)
            n1 = 0.0;
        else {
            t1 *= t1;
            n1 = t1 * t1 * dot(grad3[gi1], x1, y1);
        }
        double t2 = 0.5 - x2 * x2 - y2 * y2;
        if (t2 < 0)
            n2 = 0.0;
        else {
            t2 *= t2;
            n2 = t2 * t2 * dot(grad3[gi2], x2, y2);
        }
        // Add contributions from each corner to get the final noise value.
        // The result is scaled to return values in the interval [-1,1].
        return 70.0 * (n0 + n1 + n2);
    }

    // Inner class to speed upp gradient computations
    // (In Java, array access is a lot slower than member access)
    private static class Grad {
        double x, y;
        Grad(double x, double y, double z) {
            this.x = x;
            this.y = y;
        }
    }
}