private:
void ambient(float, float, float, float);
void diffuse(float, float, float, float);
void specular(float, float, float, float);
void emission(float, float, float, float);
private:
void ambient(float, float, float, float);
void diffuse(float, float, float, float);
void specular(float, float, float, float);
void emission(float, float, float, float);