Function shader

src/webgl/p5.Shader.js:1165–1300

(p5, fn)

};

function shader(p5, fn){
  /**
   * A class to describe a shader program.
   *
   * Each `p5.Shader` object contains a shader program that runs on the graphics
   * processing unit (GPU). Shaders can process many pixels or vertices at the
   * same time, making them fast for many graphics tasks. They’re written in a
   * language called
   * <a href="https://developer.mozilla.org/en-US/docs/Games/Techniques/3D_on_the_web/GLSL_Shaders" target="_blank">GLSL</a>
   * and run along with the rest of the code in a sketch.
   *
   * A shader program consists of two files, a vertex shader and a fragment
   * shader. The vertex shader affects where 3D geometry is drawn on the screen
   * and the fragment shader affects color. Once the `p5.Shader` object is
   * created, it can be used with the <a href="#/p5/shader">shader()</a>
   * function, as in `shader(myShader)`.
   *
   * A shader can optionally describe *hooks,* which are functions in GLSL that
   * users may choose to provide to customize the behavior of the shader. For the
   * vertex or the fragment shader, users can pass in an object where each key is
   * the type and name of a hook function, and each value is a string with the
   * parameter list and default implementation of the hook. For example, to let users
   * optionally run code at the start of the vertex shader, the options object could
   * include:
   *
   * ```js
   * {
   *   vertex: {
   *     'void beforeVertex': '() {}'
   *   }
   * }
   * ```
   *
   * Then, in your vertex shader source, you can run a hook by calling a function
   * with the same name prefixed by `HOOK_`:
   *
   * ```glsl
   * void main() {
   *   HOOK_beforeVertex();
   *   // Add the rest ofy our shader code here!
   * }
   * ```
   *
   * Note: <a href="#/p5/createShader">createShader()</a>,
   * <a href="#/p5/createFilterShader">createFilterShader()</a>, and
   * <a href="#/p5/loadShader">loadShader()</a> are the recommended ways to
   * create an instance of this class.
   *
   * @class p5.Shader
   * @constructor
   * @param {p5.RendererGL} renderer WebGL context for this shader.
   * @param {String} vertSrc source code for the vertex shader program.
   * @param {String} fragSrc source code for the fragment shader program.
   * @param {Object} [options] An optional object describing how this shader can
   * be augmented with hooks. It can include:
   *  - `vertex`: An object describing the available vertex shader hooks.
   *  - `fragment`: An object describing the available frament shader hooks.
   *