By Singular nouns, Affirmative sentences

Hi, I'd lke to offer some comments. - About "...so...as..." 1. The Emperor Augustus, it appears, commissioned an idealized sculptured portrait, the features of which are so unrealistic as to constitute what one scholar calls an "artificial face." My question is why can use "so... as"...

Dear,I am going to take GMAT exam. When I was practising, I met some grammar problems. Please help me to understand correctly about them.- About "...so...as..." 1. The Emperor Augustus, it appears, commissioned an idealized sculptured portrait, the features of which are so unrealistic as to...