[The above graphic is an interactive 3D bar graph. If you can't see it, it's probably because your browser sucks can't render WebGL content. Maybe try Chrome or Firefox?]

Ben Fry and Casey Reas, the initiators of the Processing project, announced at the Eyeo Festival that a new version of Processing, Processing 2.0, will be released in the fall (VIDEO). This 2.0 release brings a lot of really exciting changes, including vastly improved 3D performance, and a brand-new high-performance video library. Perhaps most interesting is the addition of publishing modes – Processing sketches can now be published to other formats other than the standard Java applet. The mode that is going to cause the most buzz around the interweb is Javascript mode: yes, Processing sketches can now be published, with one click, to render in pretty much any web browser. This is very exciting news for those of us who use Processing for data visualization – it means that our sketches can reach a much broader audience, and that the visual power of Processing can be combined with the interactive power of Javascript.

While preview releases of Processing 2.0 will be available for download very soon, you don’t have to wait to experiment with Processing and Javascript. The upcoming JS mode comes thanks to the team behind Processing.js, and we can use it to build sketches for the browser right now.

To get started, you can download this sample file. When you unzip the file, you’ll see a directory with three files – the index.html page, processing.js, and our sketch file, called tutorial.pde. If you open the sketch file in a text editor, you’ll see something like this:

void setup() {
  //instructions in here happen once when the sketch is run
  size(500,500);
  background(0);
}

void draw() {
  //instructions in here happen over and over again
}

If you’re a Processing user, you’ll be familiar with the setup and draw enclosures. If you’re not, the notes inside of each one explain what’s going on: when we run the sketch, the size is set to 500px by 500px, and the background is set to black. Nothing is happening (yet) in the draw enclosure.

You can see this incredibly boring sketch run if you open the index.html file in your browser (this will work in Firefox and Safari, but not in Chrome due to security settings).

Processing.js is a fully-featured port of Processing – all of the things that you’d expect to be able to do in Processing without importing extra libraries can be done in Processing.js. Which, quite frankly, is amazing! This means that many of your existing sketches will run, with no changes, in the browser.

Since this is a data visualization tutorial, let’s look at a simple representation of numbers. To keep it simple, we’ll start with a set of numbers: 13.4, 14.5, 15.0, 23.2, 30.9, 31.3, 32.9 35.1, 34.3. (These numbers are obesity percentages in the U.S. population, between the 1960s and the present – but we’re really going to use them without context).

Typically, if we were to put these numbers into a Processing sketch, we’d construct an array of floating point numbers (numbers with a decimal place), which would look like this:

float[] myNumbers = {13.4, 14.5, 15.0, 23.2, 30.9, 31.3, 32.9, 35.1, 34.3};

However, we’re not in Java-land anymore, so we can make use of Javascript’s easier syntax (one of the truly awesome things about Processing.js is that we can include JS in our sketches, inline):

var numbers = [13.4, 14.5, 15.0, 23.2, 30.9, 31.3, 32.9, 35.1, 34.3];

Our .pde file, then, looks like this:

var numbers = [13.4, 14.5, 15.0, 23.2, 30.9, 31.3, 32.9, 35.1, 34.3];

void setup() {
  //instructions in here happen once when the sketch is run
  size(500,500);
  background(0);
}

void draw() {
  //instructions in here happen over and over again
}

Now that we have our helpful list of numbers (called, cleverly, ‘numbers’), we can access any of the numbers using its index. Indexes in Processing (and Javascript) are zero-based, so to get the first number out of the list, we’d use numbers[0]. To get the fourth one, we’d use numbers[3]. Let’s use those two numbers to start doing some very (very) simple visualization. Indeed, the first thing we’ll do is to draw a couple of lines:

var numbers = [13.4, 14.5, 15.0, 23.2, 30.9, 31.3, 32.9, 35.1, 34.3];

void setup() {
  //instructions in here happen once when the sketch is run
  size(500,500);
  background(0);

  //Draw two lines
  stroke(255);
  line(0, 50, numbers[0], 50);
  line(0, 100, numbers[4], 100);
}

void draw() {
  //instructions in here happen over and over again
}

OK. I’ll admit. That’s a pretty crappy sketch. But, we can build on it. Let’s start by making those lines into rectangles:

var numbers = [13.4, 14.5, 15.0, 23.2, 30.9, 31.3, 32.9, 35.1, 34.3];

void setup() {
  //instructions in here happen once when the sketch is run
  size(500,500);
  background(0);

  //Draw two lines
  stroke(255);
  rect(0, 50, numbers[0], 20);
  rect(0, 100, numbers[4], 20);
}

void draw() {
  //instructions in here happen over and over again
}

At this point, I’m going to introduce my very best Processing friend, the map() function. What the map() function allows us to do is to adjust a number that exists in a certain range so that it fits into a new range. A good real-world example of this would be converting a number (0.5) that exists in a range between 0 and 1 into a percentage:

50 = map(0.5, 0, 1, 0, 100);

We can take any number inside any range, and map it to a new range. Here are a few more easy examples:

500 = map(5, 0, 10, 0, 1000);
0.25 = map(4, 0, 16, 0, 1);
PI = map(180, 0, 360, 0, 2 * PI);

In our sketch, the list of numbers that we’re using ranges from 13.4 to 34.3. This means that our rectangles are pretty short, sitting in the 500 pixel-wide sketch. So, let’s map those numbers to fit onto the width of our screen (minus 50 pixels as for a buffer):

var numbers = [13.4, 14.5, 15.0, 23.2, 30.9, 31.3, 32.9, 35.1, 34.3];

void setup() {
  //instructions in here happen once when the sketch is run
  size(500,500);
  background(0);

  //Draw two rectangles
  rect(0, 50, map(numbers[0], 0, 34.3, 0, width - 50), 20);
  rect(0, 100, map(numbers[4], 0, 34.3, 0, width - 50),  20);
}

void draw() {
  //instructions in here happen over and over again
}

Two bars! Wee-hoo! Now, let’s use a simple loop to get all of our numbers on the screen (this time we’ll use the max() function to find the biggest number in our list):

var numbers = [13.4, 14.5, 15.0, 23.2, 30.9, 31.3, 32.9, 35.1, 34.3];

void setup() {
  //instructions in here happen once when the sketch is run
  size(500,500);
  background(0);

  for (var i = 0; i < numbers.length; i++) {
    //calculate the width of the bar by mapping the number to the width of the screen minus 50 pixels
    var w = map(numbers[i], 0, max(numbers), 0, width - 50);
    rect(0, i * 25, w, 20);
  }
}

void draw() {
  //instructions in here happen over and over again
}

We’re still firmly in Microsoft Excel territory, but we can use some of Processing’s excellent visual programming features to make this graph more interesting. For starters, let’s change the colours of the bars. Using the map() function again, we’ll colour the bars from red (for the smallest number) to yellow (for the biggest number):

var numbers = [13.4, 14.5, 15.0, 23.2, 30.9, 31.3, 32.9, 35.1, 34.3];

void setup() {
  //instructions in here happen once when the sketch is run
  size(500,500);
  background(0);

  for (var i = 0; i < numbers.length; i++) {
    //calculate the amount of green in the colour by mapping the number to 255 (255 red &amp; 255 green = yellow)
    var c = map(numbers[i], min(numbers), max(numbers), 0, 255);
    fill(255, c, 0);
    //calculate the width of the bar by mapping the number to the width of the screen minus 50 pixels
    var w = map(numbers[i], 0, max(numbers), 0, width - 50);
  	rect(0, i * 25, w, 20);
  }
}

void draw() {
  //instructions in here happen over and over again
}

This process of mapping a number to be represented by a certain dimension (in this case, the width of the bars along with the colour) is the basic premise behind data visualization in Processing. Using this simple framework, we can map to a whole variety of dimensions, including size, position, rotation, and transparency.

As an example, here is the same system we saw above, rendered as a radial graph (note here that I’ve added a line before the loop that moves the drawing point to the centre of the screen; I’ve also changed the width of the bars to fit in the screen):

var numbers = [13.4, 14.5, 15.0, 23.2, 30.9, 31.3, 32.9, 35.1, 34.3];

void setup() {
  //instructions in here happen once when the sketch is run
  size(500,500);
  background(0);

  //move to the center of the sketch before we draw our graph
  translate(width/2, height/2);
  for (var i = 0; i < numbers.length; i++) {
    //calculate the amount of green in the colour by mapping the number to 255 (255 red &amp; 255 green = yellow)
    var c = map(numbers[i], min(numbers), max(numbers), 0, 255);
    fill(255, c, 0);
    //calculate the width of the bar by mapping the number to the half the width of the screen minus 50 pixels
    var w = map(numbers[i], 0, max(numbers), 0, width/2 - 50);
  	rect(0, 0, w, 20);
  	//after we draw each bar, turn the sketch a bit
  	rotate(TWO_PI/numbers.length);
  }
}

void draw() {
  //instructions in here happen over and over again
}

So far we’ve been keeping things very simple. But the possibilities using Processing and Javascript are really exciting. It’s very easy to add interactivity, and it’s even possible to take advantage of Processing’s 3D functionality in the browser.

Here’s our numbers again, rendered in 3D (note the change to the size() function), with the rotation controlled by the mouse (via our new friend the map() function):

var numbers = [13.4, 14.5, 15.0, 23.2, 30.9, 31.3, 32.9, 35.1, 34.3];

void setup() {
  //instructions in here happen once when the sketch is run
  size(500,500,P3D);
  background(0);

}

void draw() {
  //instructions in here happen over and over again
  background(0);
  //turn on the lights so that we see shading on the 3D objects
  lights();
  //move to the center of the sketch before we draw our graph
  translate(width/2, height/2);
  //Tilt about 70 degrees on the X axis - like tilting a frame on the wall so that it's on a table
  rotateX(1.2);
  //Now, spin around the Z axis as the mouse moves. Like spinning that frame on the table around its center
  rotateZ(map(mouseX, 0, width, 0, TWO_PI));
  for (var i = 0; i < numbers.length; i++) {
    //calculate the amount of green in the colour by mapping the number to 255 (255 red &amp; 255 green = yellow)
    var c = map(numbers[i], min(numbers), max(numbers), 0, 255);
    fill(255, c, 0);
    //calculate the height of the bar by mapping the number to the half the width of the screen minus 50 pixels
    var w = map(numbers[i], 0, max(numbers), 0, width/2 - 50);
    //move out 200 pixels from the center
  	pushMatrix();
  		translate(200, 0);
  		box(20,20,w);
  	popMatrix();
  	//after we draw each bar, turn the sketch a bit
  	rotate(TWO_PI/numbers.length);
  }
}

Thirty lines of code, and we have an interactive, 3D data visualization (you can see this sketch running inline in the header). Now, I understand that this isn’t the best use of 3D, and that we’re only visualizing a basic dataset, but the point here is to start to imagine the possibilities of using Processing with Javascript in the browser.

For starters, Javascript lets us very easily import data from any JSON source with no parsing whatsoever – this means we can create interactive graphics that load dynamic data on the fly (more on this in the next tutorial). On top of that, because we can write Javascript inline with our Processing code, and we can integrate external Javascript functions and libraries (lie JQuery) to our sketches, we can incorporate all kinds of advanced interactivity.

I suspect that the release of Processing 2.0 will lead to a burst of Javascript-based visualization projects being released on the web. In the meantime, we can use the basic template from this tutorial to work with Processing.js – have fun!