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==Background==
The processing.js project was started by John Resig who wanted to utilize the HTML5 canvas element and take advantage of the Java Processing language. It took about seven months to get a working version, consisting of 5000 lines of code but it was not a complete port of the Processing language. (Resig 2008)The project, similarly to other open source products, was released with the hope that a developer community will converge around it and contribute to development. In September 2009, we began the work to complete the port to JavaScript. In order to facilitate an architecture for participation the source code had to be readily available and the inner workings of the project and the missing functionality must be publicized. To this end the source code was made available publicly on GitHub and an issue tracking system was used to manage the large number of issues needed to be resolved in order to complete the port. A review process was setup to ensure that the code submitted was of sufficient quality.
From it's inception, Processing.js was designed to be more than just a rewrite of the Java functions provided by Processing to JavaScript. “In development I worked in John Resig wrote the original Processing.js parser to scan a backwards mannerProcessing sketch for hints of Java code and convert that code to JavaScript. Instead of building However, if the API up from parser encountered JavaScript code, it would leave the ground - I worked from code intact. This method allowed not only for the top, down, implementing enough conversion of existing Processing code to JavaScript but the API injection of JavaScript into Processing sketches as well. By allowing JavaScript to get individual demos workingexist within a Processing Sketch intact,Java and JavaScript code can exist together without any need to declare the language you are using. Old sketches written for Processing will work but new sketches written for Processing.” -http://ejohnjs can not only have Processing code but can make use of JavaScript to interact with other elements of the webpage.org/blog/processingjs/
The original code for Processing.js is more than just a Processing parser re-written in used regular expressions to convert Java into JavaScriptwhen it was encountered. It is designed in a way that connects did this by scanning for hints of Java code within the entire sketch and then replaced the Processing language (also known as P5) Java code with web technologies such as its JavaScript equivalent. Due to the difference in how Java and JavaScriptaccessed object properties from methods inside an object, the HTML5 canvas element, JQuery, and various web serviceswith statement was used as a simple solution to avoid having to prepend all function calls with "this." or "Processing.". FurthermoreHowever, Processingthe use of the with statement also meant that the JavaScript generated would fall off Trace /*cite trace paper here...js is built do we need to talk about trace in such a way as the back ground section???*/ making the code run slower than it needed to allow easy integration in some browsers. Later this method of scanning the entire sketch was replaced by the creation of new technologies an abstract syntax tree that broke up the code into smaller pieces. Each piece then had the regular expressions applied to change it. This made it was easier to apply the regular expressions correctly without accidentally converting code that was already working. It also made it easier to create proper inheritance structures and attach properties and methods to the correct object in the hierarchy chain as they emergesmaller pieces of code was being converted at any one time.
==3D support==
The introduction of the <canvas> tag into the HTML5 specification allowed Processing to be ported to JavaScript, thus enabling users to run 2D sketches within the browser without additional plug-ins. At the time when porting began, there was no plug-in free method of delivering 3D content. This limited Processing.js to its 2D functions. WebGL, A JavaScript API that is based on OpenGL ES 2.0, is now being implemented by Firefox, Chrome and Safari. It is now has become a viable candidate for use in Processing.js to render 3D sketches. Additionally, since WebGL closely matches OpenGL which is used by Processing, it substantially aided the porting processof the 3D Processing functions was relatively straight forward.
===Differencesbetween OpenGL and WebGL===The matter of porting Processing (which uses OpenGL/*1.x?? if it was opengl 2.0 it would have been even easier right?*/) was simplified because the WebGL interface is similar that of OpenGL, but there are a number of differences between the interfaces. Arguably, the The single largest difference between WebGL and OpenGL 1.x is that like OpenGL ES 2.0, the fixed-function pipeline was been removed. Because of this, not all Processing source code could not be ported directly. Instead, user-defined vertex and fragment shaders were necessary to write for lighting operations. Since some shapes in Processing aren't lit and others were, multiple shaders were written. One shader exists for lit objects such as boxes and spheres, another less complex shader was written for unlit objects such as lines and points.
The following shaders are used for rendering unlit shapes specified with begin/end function calls.
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===Typed Arrays===
[http://weblog.bocoup.com/javascript-typed-arrays link]
Because typed arrays are only available for pre-release browsers, they cannot currently be used in 2D sketches. Once they become implemented in browsers, a significant amount of the Processing.js code base can make use of these structures, increasing performance throughout the library. ===Specification Changes and Browser Inconsistencies===As the specification is concurrently implemented in different browsers, several inconsistencies between browsers have appeared. These range from minor issues, such as Minefield and Chrome/Chromium return "function" while WebKit returns "object" when the type of a typed array is queried. Another is the way WebGL's readPixels() function is implemented. This function isn't used extensively in the library itself/* andor, but it is used mike said its in the Processing.js reference testing framework. ===Problems===WebGL provides a close match to OpenGL for incorporating 3D into Processing.js, but it does present some issues when trying to port over code. There are interface differences, changes to the interface are common, and some functionality isn't available at all such as point smoothing. ==Browser Unification== One important feature provided by Processing.js is that it hides the differences between browsers. Web standards are often loosely defined, and thus variations can exist. These variations not only exist between different browser vendors but can even exist between versions of the same browser on different platforms. Something as simple as key events can vary widely between browsers. Processing.js hides all these intricacies from the user keeping it simple for content creators. ???*/
==Conclusion==
==References==
=Notes=