crayon.js

A Node-based Shader Library for Three.js

A complex code sample showcasing the API flexibility

	// Init Shader Nodes
	sceneNode = new CRAYON.SceneNode();
	sceneDepthNode = new CRAYON.SceneDepthNode( sceneNode );

	edgeNode = new CRAYON.EdgeFilterNode( renderer );
	multiplyNode = new CRAYON.MultiplyNode( renderer );
	edgeFloatNode = new CRAYON.FloatEncoderNode( edgeNode ); // Read texture back to floats

	screenNode = new CRAYON.RenderToScreenNode( renderer ); // Renders to screen

	executorNode = new CRAYON.ExecutorNode( renderer ); // All graph end points should connect to ExecutorNode to be executed
	
	// Connect the nodes
	sceneNode.connect( sceneDepthNode ); // For depth
	sceneDepthNode.connect(edgeNode, 'texture') // For applying sobel edge filter
	edgeNode.connect(multiplyNode, 'texture1') // MultipleNode takes in first texture from outlines
	sceneNode.connect(multiplyNode, 'texture2') // MultipleNode takes in 2nd texture from the scene
	multiplyNode.connect(screenNode, 'texture'); // Renders multiple operator to screen
	edgeFloatNode.connect(executorNode, 'edge'); // Connect float encoder and read pixels to Executor
	
	// In the render loop
	executorNode.renderAll(); // Calculates all node dependencies, execute them and render to screen
	

##Q&A

Why Crayon?

• Useful for prototyping shader systems
• Each node encapsulates its own code, so its resuable
• Each node have a renderTarget or an output
• Makes it easy to rewire nodes without spaghetti code
• For managable post-processing rendering

Why is this called Crayon?

1. Crayons are for drawing or learning how to. I think we started with crayon when we were kids. I hope this library is akin to digital crayons, where I start to explore creating beautiful drawing and paintings.
2. This library was created to help myself when I decided to work on some NPR (Non-Photorealistic Rendering) experiments eg. pencil, toon, watercolor shadings. Perhaps, I might be able to create an interactive crayon shader one day.

Is this yet another post-processing / shader library?

Well kinda. Not that I think writing my own code is the the best, but...

• It started from wanting to scratch my own itch
• Because I wanted to explore writing some NPR filters which are slightly more complex,
• I wanted to ease the pain working on post-processing with three.js
• I thought a Node-based approach is the way to go. (Similar to WebAudioAPI, Quartz Composer, Houdini, Nuke I think. Perhaps one day I'll build a node base UI for this as well :)
• I'm experimenting and learning on the way

Just in case you're looking for related node-based / post-processing stuff

• Three.js examples uses EffectComposer by @alteredq. They come right out of the box with three.js
• @thespite is working on Wagner, his improved version of EffectComposer
• ShaderGraph by Unconed. Pretty much uses a node based approach, and is used to power MathBox.
• PP.js also a post-processing library for three.js with a fluent-style api.
• Seriously.js Node based compositor for videos with WebGL.
• ThreeNodes.js A web-based Visual Node-base system for Three.js
• Reflektor Sandbox Graph A rather nice node library for the Reflektor project.