implementation of https://web.archive.org/web/20160418004149/http://freespace.virgin.net/hugo.elias/graphics/x_water.htm

Waves-pixelated.pde

import processing.core.PApplet;
import processing.core.PGraphics;
import processing.core.PImage;

public class MainApp extends PApplet{

    public static void main(String[] args) {
        PApplet.main("MainApp");

    }


    float damping = .8f;

    float[][] prev ;
    float[][] curr;

    int w;
    int h;
    int res =  22;

    public void settings() {
        fullScreen(1);
//        size(800, 600);
    }

    public void setup() {
        frameRate(60);
        w = (width+5)/res;
        h = (height+5)/res;
        println(w+":"+h);
        noStroke();
        fill(0);
        rectMode(CENTER);
        rect(width/2,height/2,width,height);

        colorMode(HSB, 255);

//        PImage img = loadImage("robot.jpg");
//        img.resize(w,h);
        prev = new float[w][h];
        curr = new float[w][h];
        for(int x = 0; x<w;x++){
            for(int y = 0; y<h; y++){
                prev[x][y] = 0;//img.get(x,y);
                curr[x][y] = 0;//img.get(x,y);
            }
        }
    }

    public void draw() {
        rainFall();

//        clearBounds();

        for(int x =1; x < w-1; x++){
            for(int y =1; y < h-1; y++){

                curr[x][y] = ((prev[x-1][y] + prev[x+1][y]+ prev[x][y+1] + prev[x][y-1])  /2 - curr[x][y])*damping;

// "voodoo magic"
//              https://web.archive.org/web/20160418004149/http://freespace.virgin.net/hugo.elias/graphics/x_water.htm


            }
        }

        for(int x = 0; x < w; x++){
        for(int y = 0; y < h; y++){
            int clr = color(180-curr[x][y]/12,curr[x][y],curr[x][y]);
            noStroke();
            fill(clr);
            rect(x*res,y*res,res,res);
        }}

        float[][] temp = prev;
        prev = curr;
        curr = temp;
    }


    int mousePressStrength = 750;
    public void mousePressed() {
        int x = mouseX/res;
        int y = mouseY/res;
        if(x>1 && x < w-1 && y > 1 && y < h-1){
            prev[x][y] = mousePressStrength;

        }
    }

    public void mouseDragged(){

        int x = mouseX/res;
        int y = mouseY/res;
        if(x>1 && x < w-1 && y > 1 && y < h-1){
            prev[x][y] = mousePressStrength;

        }
    }

    public boolean surfaceTouchEvent(MotionEvent me) {
        // Number of places on the screen being touched:
        int numPointers = me.getPointerCount();
        for(int i = 0; i < numPointers; i++){

        }
    }

    void rainFall(){
        if(frameCount%32==0){
            int x = round(random(w-1));
            int y = round(random(h-1));
            prev[x][y] = 200;
        }

        if(frameCount%16==0){
            int x = round(random(w-1));
            int y = round(random(h-1));
            prev[x][y] = 150;
        }

        if(frameCount%8==0){
            int x = round(random(w-1));
            int y = round(random(h-1));
            prev[x][y] = 40;
        }
    }

}