How to tell if a guy is interested?

So recently I got cast as a main character in a musical. The character I’m playing has a love interest. Long story short, when I figured out who was playing my love interest in the show, my brain kinda ended up tricking me into developing a crush on him. This happens with actors because they have to pretend to actually like that person playing their love interests which leads to it becoming reality. Him and I haven’t done one on one scenes yet, but we have read the script as a full cast. Or a read through as actors call it. Him and I have made eye contact a lot, and that’s pretty much it cause we haven’t talked to each other or had one on one rehearsals with each other yet. So this left me wondering if he possibly feels the same way about me. Or if he is developing a crush on me, or is intrigued by me like I am with him. So I was wondering: How do you know if someone is interested in you without talking to them? There has to be some way to know right?