How are emotions created? As much as I understand, emotions are simply created by thoughts in your mind. This is in the thought process of Mental Formations, not Perceptions. Perceptions don't create emotions, although Mental Formations arise from our stories about perceptions. Mental Formations create emotions. Perception just labels things.
For example, suppose I see somebody outside on the street right now, on the sidewalk there, and they're waving their arms madly. What I see is a person waving their arms. My Perception of this person is, "a nut!", or simply, "a person waving their arms". Now, they're distracting me, so maybe I have a sense of dislike. I have a Vedana, (feeling, sensation), that's unpleasantly arising because of the person waving their arms. My Vedana is unpleasant. Then perhaps my Mental Formations start disliking that person. I have an emotion then, my emotion is aversion toward that person.
Now, let us suppose that one of you sees that I'm looking out there, you turn, look out, and think, "Oh my gosh, it's my cousin! I haven't seen him in five years!", and he's waving right at you. You're going to have a Perception that's different to mine. You're going to have a Vedana that's pleasant, all of a sudden, "My cousin! Oh, I haven't seen him in so long (This is a nice cousin, of course!) "My cousin!" Your Vedana's going to be very pleasant; and your Mental Formations will start to go off, until, all of a sudden, "Oh my gosh!", your Perception's going to change; your Vedana's going to change, because, "What are they doing this to me now for? I can't talk to them now - they should know better - why don't they go away?" All of a sudden, now you're into a negative emotion, because your Vedana became negative, because it's the wrong time for your cousin to be bothering you.
That's just a little example of how Mental Formations are what's going to create your emotions. It is based on Perceptions, but caused by Mental Formations. It's also based on your Vedana. Vedana and Perceptions just come automatically. There's nothing really in between them, they're going to come automatically. Based on that, you're going to create Mental Formations, which then become your emotions.