This depends solely on context. If I were to say..
The art was unique and complicated. (You don't need a comma.)
BUT you do in the case below.
The unique, complicated art mesmerized the crowd. (Need comma)
You need commas between adjectives if when (BOTH) they can be interchanged and there is no words like AND and OR.
For example, I could also say, "The complicated, unique art..." because it does not change the meaning of the sentence.