Color Phong::shade(Ray ray, const IntersectionData& data)
{
    Color ambient;
    float ambientCoefficient = 0.005;
    ambient = ambientCoefficient * color * lightPower / (data.p - lightPos).lengthSqr(); //ambient
    Vector lightDir = lightPos - data.p;
    lightDir.normalize();

    double diffuseCoefficient = std::max(0.0, dot(lightDir, data.normal));
    Color diffuse = diffuseCoefficient * color * lightPower; // diffuse

    //specular
    Vector cameraPos = Vector(0, 165, 0);
    Vector surfaceToCamera = cameraPos - data.p;
    surfaceToCamera.normalize();

    Vector reflect = lightDir - 2.0 * dot(data.normal, lightDir) * data.normal;

    float shininess = 80.0;
    double specularCoefficient = 0.0;
    if (diffuseCoefficient > 0.0)
    {
        specularCoefficient = std::pow(std::max(0.0, dot(surfaceToCamera, reflect)), shininess);
    }
    Color specularColor = Color(1.0, 1.0, 1.0);
    Color specular = specularCoefficient * specularColor * lightPower;

    //attenuation
    float lightAttenuation = 0.2;
    float distanceToLight = (lightPos - data.p).length();
    float attenuation = 1.0 / (1.0 + lightAttenuation * std::pow(distanceToLight, 2));

    //linear color (before gamma correction)
    Color linear = ambient + attenuation * (diffuse + specular);

    //final color (after gamma correction)
    linear.operator*=(1.0/2.2);

    return linear;
}