--- language: "Processing" filename: learnprocessing.pde contributors: - ["Phone Thant Ko", "http://github.com/phonethantko"] --- ## Introduction Processing is a programming language for creation of digital arts and multimedia content, allowing non-programmers to learn fundamentals of computer programming in a visual context. While the language is based on Java language, its syntax has been largely influenced by both Java and Javascript syntaxes. [See more here](https://processing.org/reference/) The language is statically typed, and also comes with its official IDE to compile and run the scripts. ```processing /* --------- Comments --------- */ // Single-line comment starts with // /* Since Processing is based on Java, the syntax for its comments are the same as Java (as you may have noticed above)! Multi-line comments are wrapped as seen here. */ /* --------------------------------------- Writing and Running Processing Programs --------------------------------------- */ // In Processing, your program's entry point is a function named setup() with a void return type. // Note! The syntax looks strikingly similar to that of C++. void setup() { // This prints out the classic output "Hello World!" to the console when run. println("Hello World!"); // Another language with a semi-column trap, ain't it? } // Normally, we put all the static codes inside the setup() method as the name suggest since it only runs once. // It can range from setting the background colours, setting the canvas size. // You will see more of them throughout this document. // If you want to run the codes indefinitely, it has to be placed in draw() method. // draw() must exist if you want the code to run continuously and obviously, there can only be one draw() method. int i = 0; void draw() { // This block of code loops forever until stopped print(i); i++; // Increment Operator! } // Now that we know how to write the working script and how to run it, // we will proceed to explore what data types and collections are supported in Processing. /* ------------------------ Datatypes & collections ------------------------ */ // According to Processing References, Processing supports 8 primitive datatypes as follows. boolean booleanValue = true; // Boolean byte byteValueOfA = 23; // Byte char charValueOfA = 'A'; // Char color colourValueOfWhiteM = color(255, 255, 255); // Colour (Specified using color() method) color colourValueOfWhiteH = #FFFFFF; // Colour (Specified using hash value) int intValue = 5; // Integer (Number without decimals) long longValue = 2147483648L; // "L" is added to the number to mark it as a long float floatValue = 1.12345; // Float (32-bit floating-point numbers) double doubleValue = 1.12345D; // Double (64-bit floating-point numbers) // NOTE! // Although datatypes "long" and "double" work in the language, // processing functions do not use these datatypes, therefore // they need to be converted into "int" and "float" datatypes respectively, // using (int) and (float) syntax before passing into a function. // There is a whole bunch of default composite datatypes available for use in Processing. // Primarily, I will brief through the most commonly used ones to save time. // String // While char datatype uses '', String datatype uses "" - double quotes. String sampleString = "Hello, Processing!"; // String can be constructed from an array of char datatypes as well. We will discuss array very soon. char source = {'H', 'E', 'L', 'L', 'O'}; String stringFromSource = new String(source); // HELLO // As in Java, strings can be concatenated using the "+" operator. print("Hello " + "World!"); // Hello World! // Array // Arrays in Processing can hold any datatypes including Objects themselves. // Since arrays are similar to objects, they must be created with the keyword "new". int[] intArray = new int[5]; int[] intArrayWithValues = {1, 2, 3}; // You can also populate with data. // ArrayList // Functions are similar to those of array; arraylists can hold any datatypes. // The only difference is arraylists resize dynamically, // as it is a form of resizable-array implementation of the Java "List" interface. ArrayList intArrayList = new ArrayList(); // Object // Since it is based on Java, Processing supports object-oriented programming. // That means you can basically define any datatypes of your own and manipulate them to your needs. // Of course, a class has to be defined before for the object you want. // Format --> ClassName InstanceName SomeRandomClass myObject // then instantiate later //or SomeRandomClass myObjectInstantiated = new SomeRandomClass(); // Processing comes up with more collections (eg. - Dictionaries and Lists) by default, // for the simplicity sake, I will leave them out of discussion here. /* ------------ Maths ------------ */ // Arithmetic 1 + 1 // 2 2 - 1 // 0 2 * 3 // 6 3 / 2 // 1 3.0 / 2 // 1.5 3.0 % 2 // 1.0 // Processing also comes with a set of functions that simplify mathematical operations. float f = sq(3); // f = 9.0 float p = pow(3, 3); // p = 27.0 int a = abs(-13) // a = 13 int r1 = round(3.1); // r1 = 3 int r2 = round(3.7); // r2 = 4 float sr = sqrt(25); // sr = 5.0 // Vectors // Processing provides an easy way to implement vectors in its environment using PVector class. // It can describe a two or three dimensional vector and // comes with a set of methods which are useful for matrices operations. // You can find more information on PVector class and its functions here. // (https://processing.org/reference/PVector.html) // Trigonometry // Processing also supports trigonometric operations by supplying a set of functions. // sin(), cos(), tan(), asin(), acos(), atan() and also degrees() and radians() for convenient conversion. // However, those functions take angle in radians as the parameter so it has to be converted beforehand. float one = sin(PI/2); // one = 1.0 // As you may have noticed, there exists a set of constants for trigonometric uses; // PI, HALF_PI, QUARTER_PI and so on... /* ------------- Control Flow ------------- */ // Conditional Statements // If Statements - The same syntax as if statements in Java. if (author.getAppearance().equals("hot")) { print("Narcissism at its best!"); } else { // You can check for other conditions here. print("Something is really wrong here!"); } // A shortcut for if-else statements can also be used. int i = 3; String value = (i > 5) ? "Big" : "Small"; // "Small" // Switch-case structure can be used to check multiple conditions more concisely. int value = 2; switch(value) { case 0: print("Nought!"); // This doesn't get executed. break; // Jumps to the next statement case 1: print("Getting there..."); // This again doesn't get executed. break; case 2: print("Bravo!"); // This line gets executed. break; default: print("Not found!"); // This line gets executed if our value was some other value. break; } // Iterative statements // For Statements - Again, the same syntax as in Java for(int i = 0; i < 5; i ++){ print(i); // prints from 0 to 4 } // While Statements - Again, nothing new if you are familiar with Java syntax. int j = 3; while(j > 0) { print(j); j--; // This is important to prevent from the code running indefinitely. } // loop()| noLoop() | redraw() | exit() // These are more of Processing-specific functions to configure program flow. loop(); // allows the draw() method to run forever while noLoop(); // only allows it to run once. redraw(); // runs the draw() method once more. exit(); // This stops the program. It is useful for programs with draw() running continuously. ``` ## Drawing with Processing Since you will have understood the basics of the language, we will now look into the best part of Processing; DRAWING. ```processing /* ------ Shapes ------ */ // 2D Shapes // Point point(x, y); // In 2D space point(x, y, z); // In 3D space // Draws a point in the coordinate space. // Line line(x1, y1, x2, y2); // In 2D space line(x1, y1, z1, x2, y2, z2); // In 3D space // Draws a line connecting two points defined by (x1, y1) and (x2, y2) // Rectangle rect(a, b, c, d, [r]); // With optional parameter defining the radius of all corners rect(a, b, c, d, tl, tr, br, bl); // With optional set of parameters defining radius of each corner // Draws a rectangle with {a, b} as a top left coordinate and c and d as width and height respectively. // Quad quad(x,y,x2,y2,x3,y3,x4,y4) // Draws a quadrilateral with parameters defining coordinates of each corner point. // Arc; arc(x, y, width, height, start, stop, [mode]); // While the first four parameters are self-explanatory, // start and end defined the angles the arc starts and ends (in radians). // Optional parameter [mode] defines the filling; // PIE gives pie-like outline, CHORD gives the chord-like outline and OPEN is CHORD without strokes ``` Processing is easy to learn and is particularly useful to create multimedia contents (even in 3D) without having to type a lot of codes. It is so simple that you can read through the code and get a rough idea of the program flow. However, that does not apply when you introduce external libraries, packages and even your own classes. (Trust me! Processing projects can get really large) ## What's Next? Here, I have compiled some useful resources: - [Processing Website](http://processing.org) - [Processing Sketches](http://openprocessing.org)