/**
  * A material
  */
struct Material {
    /**
      * The diffuse sampler
      */
    sampler2D diffuse;

    /**
      * The diffuse sampler
      */
    sampler2D specular;

    /**
      * The shininess value
      */
    float metallic;

    /**
      * The shininess value
      */
    float roughness;

    /**
      * The shininess value
      */
    float ior;

    /**
      * The shininess value
      */
    float alpha;
};