// lens demo
// author: info@toxi.co.uk

// curvature of the lens: 1 = normal spherical, >1 = increasingly extreme distortion
// 0 = flat zoom, < -1 = inverse lens (as seen from inside the lens)
float curvature=1;
int gridSize=10;
BImage tex;
float radius=0,maxRadius=100;

void setup() {
  size(200,200);
  noStroke();
  tex=loadImage("milan_rubbish.jpg");
}

void loop() {
  background(200);
  // click mouse to increase effect at position
  if (mousePressed) {
    radius+=(maxRadius-radius)*0.1;
  } else {
    radius*=0.98;
  }
  if (curvature<0) translate(0,0,-100);
  for(int y=0; y<=height; y+=gridSize) {
    float sqy=sq(mouseY-y), sqy1=sq(mouseY-(y+gridSize));
    beginShape(TRIANGLE_STRIP);
    texture(tex);
    for(int x=0; x<=width; x+=gridSize) {
      vertex(x,y,min(max(radius-sqrt(sq(mouseX-x)+sqy)*curvature,0),200),x,y);
      vertex(x,y+gridSize,min(max(radius-sqrt(sq(mouseX-x)+sqy1)*curvature,0),200),x,y+gridSize);
    }
    endShape();
  }
}