​

let y = 0;

let vel = 0.001;

​

let bg;

​

function preload() {

  bg = loadImage("background.png");

  scannerShader = loadShader("scanner.vert", "scanner.frag");

}

​

function setup() {

  createCanvas(600, 600, WEBGL);

  shader(scannerShader);

  scannerShader.setUniform("background", bg);

}

​

function draw() {

  scannerShader.setUniform("yPos", y);

  rect(0, 0, width, height);

  y += vel;

  if(y <= 0 || y >= 1) {

    vel *= -1;

  }

}

​