glslCanvas

Simple GLSL Fragment Shader Sandbox

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GlslCanvas is JavaScript Library that helps you easily load GLSL Fragment and Vertex Shaders into an HTML canvas. I have used this in my Book of Shaders and glslEditor.
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How to use it?

There are different ways to do this. But first, make sure you are loading the latest version of ``GlslCanvas.js`` on your page by adding this line to your HTML:
<script type="text/javascript" src="https://rawgit.com/patriciogonzalezvivo/glslCanvas/master/dist/GlslCanvas.js"></script>

or if you are using npm package manager on your console do:
npm install glslCanvas

The easy way

  1. Create a canvas element in your HTML.
  2. Add the class name ``glslCanvas`` to the canvas.
  3. Assign it a shader...
* through a url using the attribute ```data-fragment-url```
* or directly writing your code inside the ```data-fragment``` attribute
<canvas class="glslCanvas" data-fragment-url="shader.frag" width="500" height="500"></canvas>

That's all! glslCanvas will automatically load a WebGL context in that ``<canvas>`` element, compile the shader and animate it for you.
As you can see, in this example we are loading the fragment shader by setting the attribute ``data-fragment-url` to a url. But there are also a few other ways to load data to our `glslCanvas``:
  • ``data-fragment`` : load a fragment shader by providing the content of the shader as a string
  • ``data-fragment-url`` : load a fragment shader by providing a valid url
  • ``data-vertex`` : load a vertex shader by providing the content of the shader as a string
  • ``data-vertex-url`` : load a vertex shader by providing a valid url
  • ``data-textures`: add a list of texture urls separated by commas (ex: `data-textures="texture.jpg,normal_map.png,something.jpg"`). Textures will be assigned in order to `uniform sampler2D` variables with names following this style: `u_tex0`, `u_tex1`, `u_tex2``, etc.

All the cached ``.glslCanvas` elements will be stored in the `windows.glslCanvases`` array.

The JS way

Create a ``<canvas>` element and construct a `glsCanvas()`` sandbox from it.
var canvas = document.createElement("canvas");
var sandbox = new GlslCanvas(canvas);

In case you need to reload the shader:

Reloading shaders from JS

You can change the content of the shader as many times as you want. Here are some examples:
// Load only the Fragment Shader
var string_frag_code = "main(){\ngl_FragColor = vec4(1.0);\n}\n";
sandbox.load(string_frag_code);

// Load a Fragment and Vertex Shader
var string_vert_code = "attribute vec4 a_position; main(){\ggl_Position = a_position;\n}\n";
sandbox.load(string_frag_code, string_vert_code);

Default Uniforms

Some uniforms are automatically loaded for you:
  • ``u_time`: a `float`` representing elapsed time in seconds.
  • ``u_resolution`: a `vec2`` representing the dimensions of the viewport.
  • ``u_mouse`: a `vec2` representing the position of the mouse, defined in Javascript with `.setMouse({x:[value],y:[value])``.
  • ``u_tex[number]`: a `sampler2D` containing textures loaded with the `data-textures`` attribute.

You can also send your custom uniforms to a shader with ``.setUniform([name],[...value])`. GlslCanvas will parse the value you provide to determine its type. If the value is a `String``, GlslCanvas will parse it as the url of a texture.
// Assign .5 to "uniform float u_brightness"
sandbox.setUniform("u_brightness",.5); 

// Assign (.2,.3) to "uniform vec2 u_position"
sandbox.setUniform("u_position",.2,.3);

// Assign a red color to "uniform vec3 u_color"
sandbox.setUniform("u_color",1,0,0); 

// Load a new texture and assign it to "uniform sampler2D u_texture"
sandbox.setUniform("u_texture","data/texture.jpg");

Quick start demo

In the ``index.html`` file, you will find handy example code to start.
Demo page: patriciogonzalezvivo.github.io/glslCanvas/

Collaborate

If you'd like to contribute to this code, you need to:
git clone https://github.com/patriciogonzalezvivo/glslCanvas.git
cd glslCanvas
yarn
  • Run rollup in dev mode while you edit
yarn run dev
  • Build for production
yarn run build
  • Push to your local fork and make your pull request

Thank you