2D water ripple shader

src_MainApp.java

import processing.core.PApplet;
import processing.core.PGraphics;
import processing.opengl.PShader;

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

    PShader waterShader;
    PGraphics[] waterBuffers;
    int waterBufferWidth = 800;
    int waterBufferHeight = 800;
    float damping = .999f;

    public void settings() {
        size(800,800,P2D);
        smooth(8);
    }

    public void setup(){
        setupWater();
    }

    public void draw(){
        updateWater();
        image(waterBuffers[1].get(), 0, 0, width, height);
    }

    private void setupWater() {
        waterShader = loadShader("waterFrag.glsl");
        waterShader.set("resolution", (float)waterBufferWidth, (float)waterBufferHeight);
        waterShader.set("damping", damping);
        waterBuffers = new PGraphics[2];
        for(int i = 0; i < waterBuffers.length; i++){
            waterBuffers[i] = createGraphics(waterBufferWidth, waterBufferHeight, P2D);
            waterBuffers[i].beginDraw();
            waterBuffers[i].background(0);
            waterBuffers[i].endDraw();
        }
    }

    private void updateWater() {
        updateBuffer1();
        swapBuffers();
    }

    private void updateBuffer1() {
        waterShader.set("buffer0", waterBuffers[0]);
        waterShader.set("buffer1", waterBuffers[1]);
        waterBuffers[1].beginDraw();
        waterBuffers[1].shader(waterShader);
        waterBuffers[1].noStroke();
        waterBuffers[1].fill(0);
        waterBuffers[1].rect(0,0,waterBufferWidth,waterBufferHeight);
        waterBuffers[1].resetShader();
        waterBuffers[1].stroke(255);
        waterBuffers[1].noFill();
        waterBuffers[1].ellipse(mouseX, mouseY, 50,50);
        waterBuffers[1].endDraw();
    }

    private void swapBuffers() {
        PGraphics temp = waterBuffers[1];
        waterBuffers[1] = waterBuffers[0];
        waterBuffers[0] = temp;
    }

}

src_waterFrag.glsl

#ifdef GL_ES
precision mediump float;
#endif

uniform vec2 resolution;
uniform sampler2D buffer0;
uniform sampler2D buffer1;
uniform float damping;

#define PI 3.14159265359

float get(sampler2D sampler, vec2 uv, vec2 off){
    return texture2D(sampler, vec2(uv.x+off.x, uv.y+off.y)).x;
}

void main(void) {
 vec2 uv = gl_FragCoord.xy / resolution.xy;
 float pixelSizeX = 1 / resolution.x;
 float pixelSizeY = 1 / resolution.y;

 float color = (get(buffer0, uv, vec2(-pixelSizeX,0)) +
                get(buffer0, uv, vec2(pixelSizeX,0)) +
                get(buffer0, uv, vec2(0,pixelSizeY)) +
                get(buffer0, uv, vec2(0,-pixelSizeY))) / 2 - get(buffer1, uv, vec2(0.));
 color *= damping;

 gl_FragColor = vec4(vec3(color),1.);
}