Java interpolate interpolatedNoise(int x, int z, int reciprocal)

Description

Gets interpolated noise for the specified coordinate pair, using the specified frequency reciprocal.

License

Open Source License

Parameter

Parameter	Description
x	The x coordinate.
z	The z coordinate.
reciprocal	The frequency reciprocal.

Return

The interpolated noise.

Declaration

private static int interpolatedNoise(int x, int z, int reciprocal) 

Method Source Code

//package com.java2s;

public class Main {
    /**/*from  ww w. j  a  va  2s  . c om*/
     * The cosine table used for interpolation.
     */
    private static final int[] COSINE = new int[2048];

    /**
     * Gets interpolated noise for the specified coordinate pair, using the specified frequency reciprocal.
     *
     * @param x The x coordinate.
     * @param z The z coordinate.
     * @param reciprocal The frequency reciprocal.
     * @return The interpolated noise.
     */
    private static int interpolatedNoise(int x, int z, int reciprocal) {
        int xt = x % reciprocal;
        int zt = z % reciprocal;

        x /= reciprocal;
        z /= reciprocal;

        int c = smoothNoise(x, z);
        int e = smoothNoise(x + 1, z);
        int ce = interpolate(c, e, xt, reciprocal);

        int n = smoothNoise(x, z + 1);
        int ne = smoothNoise(x + 1, z + 1);
        int u = interpolate(n, ne, xt, reciprocal);

        return interpolate(ce, u, zt, reciprocal);
    }

    /**
     * Computes smooth noise for the specified coordinate pair.
     *
     * @param x The x coordinate.
     * @param z The z coordinate.
     * @return The smooth noise.
     */
    private static int smoothNoise(int x, int z) {
        int corners = noise(x - 1, z - 1) + noise(x + 1, z - 1) + noise(x - 1, z + 1) + noise(x + 1, z + 1);
        int sides = noise(x - 1, z) + noise(x + 1, z) + noise(x, z - 1) + noise(x, z + 1);
        int center = noise(x, z);

        return corners / 16 + sides / 8 + center / 4;
    }

    /**
     * Interpolates two smooth noise values.
     *
     * @param a The first smooth noise value.
     * @param b The second smooth noise value.
     * @param theta The angle.
     * @param reciprocal The frequency reciprocal.
     * @return The interpolated value.
     */
    private static int interpolate(int a, int b, int theta, int reciprocal) {
        int cosine = 65536 - COSINE[theta * COSINE.length / (2 * reciprocal)] / 2;
        return (a * (65536 - cosine)) / 65536 + (b * cosine) / 65536;
    }

    /**
     * Computes noise for the specified coordinate pair.
     *
     * @param x The x coordinate.
     * @param z The z coordinate.
     * @return The noise.
     */
    private static int noise(int x, int z) {
        int n = x + z * 57;
        n = (n << 13) ^ n;
        n = (n * (n * n * 15731 + 789221) + 1376312589) & Integer.MAX_VALUE;
        return (n >> 19) & 0xff;
    }
}

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