Is it a sin to sell a dog? I always use a real chess board when playing chess online or off.
Cheating on material chessboard?

Absolutely not. Not everyone can see the game as well, on a 2-D screen, as they can with an actual chessboard in front of them.
Why in the world would you consider that cheating?
In order for it to be cheating, it would have to be against the rules. Nowhere in the rules does it say you can't do that. Furthermore, there would be no way to enforce it.
You could also drink a milkshake or drive on inline skates while playing on your smartphone and you stil wouldn't be cheating. Oh how about sitting in your private whirlpool and playing chess? *-*
It is cheating when someone use material(real) chessboard instead of this on the monitor (without moving pieces in live chess) to play?