@gerhobbelt/shadergraph

shadergraph

Functional GLSL linker

ShaderGraph is a library for linking together GLSL snippets into stand-alone shaders. It is mainly meant to build complicated shaders 100% programmatically. But it can also act as the back-end to a live graph-based shader editor, as its graph model is persistent.

Snippets can be simple one-liners, or multi-function source files. Snippets can also declare callbacks, as functions without bodies, linked in from elsewhere. This allows complicated execution flows to be built very easily.

vec3 getColor();
void main() {
  gl_FragColor = vec4(getColor(), 1.0);
}

ShaderGraph is designed to play well with Three.js, but does not depend on it. It merely follows the same code/object conventions.

There is no editing UI included, only a way to display a graph as an HTML/CSS/SVG diagram.

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Live Examples

ShaderGraph

• Require
• Combined Vertex/Fragment Material
• Instanced Uniform
• De-duped Attributes
• Split Outputs
• Fanned Outputs
• Passed Outputs
• Isolate Subgraphs
• Deep Nesting
• Deep Callback
• Isolated require

ShaderGraph 2 drives all shaders in MathBox² (in development). For more info, see the articles on acko.net:

• ShaderGraph 2
• MathBox²

Here's a real-world vertex shader for a line primitive, sampling color and position from two textures:

You can also use ShaderGraph's graph visualizer directly for other purposes:

• Raw Graph

Basic Use

Install via bower:

bower install shadergraph

Include build/shadergraph.js.

To use ShaderGraph, you initialize it once with a given snippet library. A snippet library is either a dictionary of named snippets, or a fetch function.

// Dynamic fetch
var fetch = function (name) {
  return "..."
};

// Static fetch
var fetch = {
  getColor:     "...",
  setColor:     "...",
  getRampColor: "...",
};

var shadergraph = ShaderGraph(fetch);

You can use the chainable Factory API to build graphs. It's a smart wrapper around a partially built graph. It allows you to make splits and joins, hook up callbacks via requires, import other factories, etc.

Instead of including snippets by name, you can also pass in GLSL code directly to .pipe(…) and .require(…) regardless of whether you are using a fetch function/library or not.

Snippets are instanced by default, letting you bind unique uniforms to specific snippets in the chain:

// Prepare new shader
var shader = shadergraph.shader()

// Prepare uniform (three.js style)
var uniforms = {
  diffuseColor: { type: 'v3', value: { x: 0.5, y: 0.75, z: 1.0 }}
};

// Build shader graph
shader
  // Require a callback
  .require('getRampColor')

  // Build two-step chain that uses the callback and the uniform
  .pipe('getColor', uniforms)
  .pipe('setColor')

var program = shader.link();

Instancing behavior can be configured globally or per shader (see below).

Materials

ShaderGraph also includes a material helper, to build a vertex/fragment shader simultaneously:

// Prepare new material (vertex + fragment shader)
var material = shadergraph.material()

// Build vertex shader graph
material.vertex
  .pipe('vertex')

// Build fragment shader graph
material.fragment
  .pipe('getColor')
  .pipe('setColor')

// Link both shaders and combine into a three.js style material
var program = material.link()

The returned program object is compatible with Three.js' ShaderMaterial objects.

Caveats

• Call shadergraph.inspect(…) anywhere to insert an inspector for a graph, and find missing/wrong connections.
• Preprocessing directives like #ifdef and #define are ignored, but do pass through. Be careful when using them. Consider using snippets and/or callbacks instead.
• Structs are not supported, glsl-parser seems to choke on them. Array types are probably a bit buggy still.

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Reference

Constructor

var fetch = function (name) { return … };
var fetch = { name: "...", name: "..." };
var config = {
  globalUniforms:   false, // Make uniforms   global
  globalVaryings:   true,  // Make varyings   global
  globalAttributes: true,  // Make attributes global
  globals:          [],    // Make specific symbols global
  autoInspect:      false, // Pop-up a graph inspector if compilation fails
}
shadergraph = ShaderGraph(fetch, config);

ShaderGraph

• .shader(config = {})
  Returns an empty shader graph wrapped in a factory. Override global config options.
• .material(config = {})
  Returns an empty material wrapping two factories: material.vertex and material.fragment. Override global config options.
• .visualize(graph/factory/material)
  Draw the given graph(s), returns an HTML element. Call element.update() after inserting.
• .inspect(graph/factory/material)
  Draw the graph and insert it into the body as a floating inspector.

Factory

• .pipe(name/code, uniforms = {}, namespace = null, defines = {})
.pipe(name/code, namespace = null, uniforms = {}, defines = {})
.pipe(name/code, uniforms = {}, defines = {})
.pipe(factory)
  Include the given code/snippet/factory and connect it to what came before. Binds dictionary of uniforms. Set the namespace.
  

• .require(name/code, uniforms = {}, namespace = null, defines = {})
.require(name/code, namespace = null, uniforms = {}, defines = {})
.require(name/code, uniforms = {}, defines = {})
.require(factory)
  Include the given code/snippet/factory as a callback for what comes next. Binds dictionary of uniforms. Set the namespace.
  

• .isolate().….end()
  Create an isolated subgraph and call it.
  

• .callback().….end()
  Create an isolated subgraph and use as a callback.
  

• .split().….next().….end()
  Create two or more branches and split connections across them 1-to-1.
  

• .fan().….next().….end()
  Create two or more branches and fan connections across them 1-to-N.
  

• .pass()
  Use this instead of .end() to make additional passthrough connections that skip the entire block.
  

• .graph()
  Finalize the graph and return it. The factory is reset to an empty state.

• .compile(name)
  Finalize the graph and compile it immediately (no callbacks). The graph is discarded.

• .link(name)
  Finalize the graph and link it with its subgraphs immediately (with callbacks). The graph is discarded.

Graph

• .compile(name)
  Compile the graph (no callbacks). The graph is retained.

• .link(name)
  Compile and link the graph and its subgraphs (with callbacks). The graph is retained.

Material

• .link(options = {}) Link the material's vertex and fragment shader. Returns Three.js style ShaderMaterial options, merged with any existing options passed in.

Manual Use

If you want to build graphs by hand instead of with factories, this is possible, but not as nice. You will need to construct objects and inject a few dependencies. Use the Factory API as a guide.

The underlying namespaces are exposed as ShaderGraph.Graph, ShaderGraph.Block, … Block and its subclasses are the logical pieces of the shader. Each block has a Node associated with it that lives in the Graph and contains a set of Outlets. Connections can be made node-to-node with node.connect(node) (auto-matching by name and type), or outlet-to-outlet with outlet.connect(outlet).

To compile Graphs created without a factory, you will need to call .compile() or .link() on the graph's tail block directly.

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Steven Wittens - http://acko.net/