Creates and loads a filter shader from an external file.
Examples
Syntax
  
      loadFilterShader(fragFilename, [successCallback], [failureCallback])
      
        Parameters
 fragFilename 
String: path to the fragment shader file
 successCallback 
Function: callback to be called once the shader is loaded. Will be passed the p5.Shader object.
 failureCallback 
Function: callback to be called if there is an error loading the shader. Will be passed the error event.
Returns
Promise<p5.Shader>: a promise that resolves with a shader object
Notice any errors or typos? Please let us know. Please feel free to edit src/webgl/material.js and open a pull request!
Related References
- copyToContext - Copies the shader from one drawing context to another. 
- inspectHooks - Logs the hooks available in this shader, and their current implementation. 
- modify - Returns a new shader, based on the original, but with custom snippets of shader code replacing default behaviour. 
- setUniform - Sets the shader’s uniform (global) variables.