glMaterialfv (GL_FRONT_AND_BACK, GL_SHININESS, front_mat_shininess);
glMaterialfv (GL_FRONT_AND_BACK, GL_SPECULAR, front_mat_specular);
glMaterialfv (GL_FRONT_AND_BACK, GL_DIFFUSE, front_mat_diffuse);
glMaterialfv (GL_BACK, GL_SHININESS, back_mat_shininess);
glMaterialfv (GL_BACK, GL_SPECULAR, back_mat_specular);
glMaterialfv (GL_BACK, GL_DIFFUSE, back_mat_diffuse);
glMaterialfv (GL_FRONT_AND_BACK, GL_SHININESS, front_mat_shininess);
glMaterialfv (GL_FRONT_AND_BACK, GL_SPECULAR, front_mat_specular);
glMaterialfv (GL_FRONT_AND_BACK, GL_DIFFUSE, front_mat_diffuse);
glMaterialfv (GL_BACK, GL_SHININESS, back_mat_shininess);
glMaterialfv (GL_BACK, GL_SPECULAR, back_mat_specular);
glMaterialfv (GL_BACK, GL_DIFFUSE, back_mat_diffuse);