PerlinChunks.java

import java.awt.Graphics;
import java.awt.image.BufferedImage;

import javax.swing.JFrame;

public class PerlinChunks {
	private static int hash32shift(int key) {
		key = ~key + (key << 15);
		key = key ^ (key >>> 12);
		key = key + (key << 2);
		key = key ^ (key >>> 4);
		key = key * 2057;
		key = key ^ (key >>> 16);
		return key;
	}

	public static float generateWhiteNoise(int x, int y) {
		return Math.abs(hash32shift(x ^ hash32shift(y))) / (float) Integer.MAX_VALUE;
	}

	static double interpolate(double x0, double x1, double alpha) {
		return x0 * (1 - alpha) + alpha * x1;
	}

	static double generateSmoothNoise(double x, double y) {
		int intX = (int) x;
		double horizontal_blend = x - intX;
		int intY = (int) y;
		double vertical_blend = y - intY;
		double top = interpolate(generateWhiteNoise(intX, intY), generateWhiteNoise(intX + 1, intY), horizontal_blend);
		double bottom = interpolate(generateWhiteNoise(intX, intY + 1), generateWhiteNoise(intX + 1, intY + 1), horizontal_blend);
		return interpolate(top, bottom, vertical_blend);
	}

	static double generatePerlinNoise(double x, double y, int octaveCount) {
		double persistance = 0.5f;
		double amplitude = 1.0f;
		double totalAmplitude = 0.0f;
		double perlinNoise = 0.0;
		for (int i = 0; i < octaveCount; i++) {
			amplitude *= persistance;
			totalAmplitude += amplitude;
			double m = Math.pow(2, i - 4);
			perlinNoise += generateSmoothNoise(x * m, y * m) * amplitude;
		}
		return perlinNoise / totalAmplitude;
	}

	private static int CHUNK_SIZE = 256;

	static double[][] generateChunk(int chunkX, int chunkY) {
		double[][] chunk = new double[CHUNK_SIZE][CHUNK_SIZE];
		for (int y = 0; y < CHUNK_SIZE; y++) {
			for (int x = 0; x < CHUNK_SIZE; x++) {
				chunk[y][x] = generatePerlinNoise(chunkX * CHUNK_SIZE + x, chunkY * CHUNK_SIZE + y, 16);
			}
		}
		return chunk;
	}

	private static BufferedImage createChunkImage(int chunkX, int chunkY) {
		double[][] generateChunk = generateChunk(chunkX, chunkY);
		BufferedImage image = new BufferedImage(generateChunk.length, generateChunk[0].length, BufferedImage.TYPE_BYTE_GRAY);
		for (int y = 0; y < image.getHeight(); y++) {
			for (int x = 0; x < image.getWidth(); x++) {
				int c = (int) (generateChunk[y][x] * 255);
				image.setRGB(x, y, 0x010101 * c);
			}
		}
		return image;
	}

	public static void main(String[] args) throws Exception {
		JFrame frame = new JFrame() {
			@Override
			public void paint(Graphics g) {
				super.paint(g);
				for (int y = 0; y <= getHeight() / CHUNK_SIZE; y++) {
					for (int x = 0; x <= getWidth() / CHUNK_SIZE; x++) {
						g.drawImage(createChunkImage(x, y), x * CHUNK_SIZE, y * CHUNK_SIZE, null);
					}
				}
			}
		};
		frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
		frame.setVisible(true);
		frame.setSize(800, 600);
	}
}