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SquidLib platform-independent logic and utility code. Please refer to https://github.com/SquidPony/SquidLib .

There is a newer version: 3.0.6

package squidpony.squidgrid.mapping;

import squidpony.annotation.Beta;
import squidpony.squidmath.PerlinNoise;

/**
 * Tools to create maps. Not commonly used outside of code that needs height maps.
 *
 * @author Eben Howard - http://squidpony.com - [email protected]
 */
@Beta
public class HeightMapFactory {
    /**
     * Returns a randomly generated map of doubles. Commonly referred to as a
     * Height Map. Uses {@link PerlinNoise} in layers to generate coherent heights.
     *
     * @param width in cells
     * @param height in cells
     * @param offset a double that changes the sampling process; often randomly generated
     * @return the created map as a 2D double array
     */
    private static final int[] perlinDivisors = {1, 1, 2, 4, 8, 16, 64};
    public static double[][] heightMap(int width, int height, double offset) {
        double[][] heightMap = new double[width][height];

        for (int x = 0; x < width; x++) {
            for (int y = 0; y < height; y++) {
                //Get noise
                double n = 0;
                double xi = width * 0.1375, yi = height * 0.1375;//Math.max(width, height);

                for (int p = 0; p < perlinDivisors.length; p++) {
                    n += PerlinNoise.noise((x + offset) / xi, (y + offset) / yi) / perlinDivisors[p];
                    xi *= 0.5;
                    yi *= 0.5;
                }
                double xdist = x - width * 0.5;
                xdist *= xdist;
                double ydist = y - height * 0.5;
                ydist *= ydist;
                double dist = Math.sqrt(xdist + ydist);
                n -= Math.max(0, Math.pow(dist / (width * 0.5), 2) - 0.4);

                heightMap[x][y] = n;
            }
        }
        return heightMap;
    }
}