/**
 * Struct for representing a material for a {@link ModelExperimental}. The model
 * rendering pipeline will pass this struct between material, custom shaders,
 * and lighting stages. This is not to be confused with {@link czm_material}
 * which is used by the older Fabric materials system, although they are similar
 *
 * @name czm_modelMaterial
 * @glslStruct
 *
 * @property {vec3} diffuse Incoming light that scatters evenly in all directions.
 * @property {float} alpha Alpha of this material. 0.0 is completely transparent; 1.0 is completely opaque.
 * @property {vec3} specular Color of reflected light at normal incidence in PBR materials. This is sometimes referred to as f0 in the literature.
 * @property {float} roughness A number from 0.0 to 1.0 representing how rough the surface is. Values near 0.0 produce glossy surfaces, while values near 1.0 produce rough surfaces.
 * @property {vec3} normalEC Surface's normal in eye coordinates. It is used for effects such as normal mapping. The default is the surface's unmodified normal.
 * @property {float} occlusion Ambient occlusion recieved at this point on the material. 1.0 means fully lit, 0.0 means fully occluded.
 * @property {vec3} emissive Light emitted by the material equally in all directions. The default is vec3(0.0), which emits no light.
 */
struct czm_modelMaterial {
    vec3 diffuse;
    float alpha;
    vec3 specular;
    float roughness;
    vec3 normalEC;
    float occlusion;
    vec3 emissive;
};