for (int index = 0, surface = 0; surface < 6; ++surface) {
for (int y = 0; y < sidelength; ++y) {
for (int x = 0; x < sidelength; ++x, ++index) {
for (int index = 0, surface = 0; surface < 6; ++surface) {
for (int y = 0; y < sidelength; ++y) {
for (int x = 0; x < sidelength; ++x, ++index) {