inline GLfloat *get_diffuse() { return diffuse; }
inline GLfloat *get_specular() { return specular; }
inline GLfloat *get_emission() { return emission; }
inline GLfloat *get_diffuse() { return diffuse; }
inline GLfloat *get_specular() { return specular; }
inline GLfloat *get_emission() { return emission; }