PImage img;       // The source image
  int cellsize = 2; // Dimensions of each cell in the grid
  int columns, rows;   // Number of columns and rows in our system
  
  void setup() {
    size(640, 360, P3D); 
    img = loadImage("eames.jpg");  // Load the image
    columns = img.width / cellsize;  // Calculate # of columns
    rows = img.height / cellsize;  // Calculate # of rows
  }
  
  void draw() {
    background(0);
    // Begin loop for columns
    for ( int i = 0; i < columns; i++) {
      // Begin loop for rows
      for ( int j = 0; j < rows; j++) {
        int x = i*cellsize + cellsize/2;  // x position
        int y = j*cellsize + cellsize/2;  // y position
        int loc = x + y*img.width;  // Pixel array location
        color c = img.pixels[loc];  // Grab the color
        // Calculate a z position as a function of mouseX and pixel brightness
        float z = (mouseX / float(width)) * brightness(img.pixels[loc]) - 20.0;
        // Translate to the location, set fill and stroke, and draw the rect
        pushMatrix();
        translate(x + 200, y + 100, z);
        fill(c, 204);
        noStroke();
        rectMode(CENTER);
        rect(0, 0, cellsize, cellsize);
        popMatrix();
      }
    }
  }