cube_material.set_diffuse(GL::Color(0.5, 0.5, 0.55));
cube_material.set_ambient(GL::Color(0.5, 0.5, 0.55));
cube_material.set_specular(GL::Color(1.0));
cube_material.set_diffuse(GL::Color(0.5, 0.5, 0.55));
cube_material.set_ambient(GL::Color(0.5, 0.5, 0.55));
cube_material.set_specular(GL::Color(1.0));