simple physically inspired shading function

gistfile1.glsl

vec3 shade(vec3 color, float roughness, float metallness){
    float fresnelFactor = 0.93;
    float specularFactor = 0.65;

    vec3 normal = normalize(vNormal);
    vec3 eyeDir = getEyeDir();

    vec3 N = normal;
    vec3 V = -eyeDir;
    vec3 reflected = reflect(eyeDir, normal);

    vec3 diffuse = textureCube3DLogLuv(envTex, normal, 1.0);
    vec3 specular = textureCube3DLogLuv(envTex, reflected, roughness);

    vec3 specularColor = specular*mix(vec3(1), color, metallness);
    vec3 diffuseColor = diffuse*color;

    float nonMetallness = 1.0-metallness;
    float glossiness = 1.0-roughness;

    float fresnel = pow(1.0-max(0.0, dot(N,V)), 3.5);
    fresnel = mix(1.0, fresnel, mix(fresnelFactor, fresnelFactor*0.2, metallness));
    float specularity = max(metallness, glossiness)*specularFactor*fresnel;

    vec3 excident = diffuseColor*nonMetallness + specularColor*specularity;

    return excident;
}