I can override my eye sight in the right conditions (with various degree of how much I override it) with another whole world created by mind in front of me. Ofc is FAR far far easier when it's dark or I am alone or I am hearing music, but you get the point.
For example when doing some shadowboxing I actually put fantasized people in front of myself which fight me and react to my moves, and I can see them as I see a real person until I remain focused. I often change also the location and the background to suite better my fantasy.
It's like shutting partially your eye system and making your mind go in full control.
edit: I said this to explain how much I can push it. But to make a simpler example, I _Very_ often fantasized at night, before bad and with eyes closed, of having an adventure in a post apocalyptic world and I can see everything in first person in my mind like I am really there and everything is real
No lie. His description sounds like he's a better visualizer than I am, but not really different in kind, just intensity. I could probably do that if I practiced more often. When I was under 15 or so it was easier and closer to what he described. But still, if I'm reading the right book I essentially cannot see the page anymore because the visualization is so strong and intense that I'm in that other world, not in ours anymore.
I recently read Clarke's The City and the Stars. His description of the city of Diaspar is so strong that I feel like I have literally been there in exactly the same way as I have been to Yellowstone. I know I can't get on a plane to go back there, but if I open the book again I will be there again.
Another favorite book of mine is The Good Earth. I have experienced Wang Lung's life in almost the exact same way as Picard experienced another man's life in The Inner Light. I read that book in a single uninterrupted sitting because the experience of living someone else's life from beginning to end was so enthralling that I could not stop.
If you want to know why Harry Potter fans are so obsessive, it's because the books are very easy to visualize. Millions of people have a "lived experience" of being Harry throughout 7 years of wizard school and that experience leaves a mark on you. When I saw the movies it was a bit odd because I'd already seen a different set of "movies" in my mind and they got some details wrong.
I used to play soccer when I was young and I would always visualize the trajectory of the ball in my mind before I kicked it. This wasn't just muscle memory (though I don't doubt there's a strong connection between the two); I would describe it like being able to see 1 second into the future and having the ability to superimpose the trajectory of the ball on the scene in front of my eyes.
I now take portraits as a side business. When I schedule photoshoots with models and think of locations, I'm constantly visualizing in my head the scene, their poses, the lighting, etc. In my head these aren't still images or snapshots, but I'm on set with the model and I'm able to move around and interact with the model to try different angles and figure out the ones I like and don't like. I never take written notes about the shots I want to try and get, I just spend the few days leading up to the shoot mulling over ideas in my head and by the day of I know exactly what shots I want and how to get them.
I also noticed as a kid that when I would read fantasy books that I would sometimes get so engrossed in the imagery and descriptions of the scenes that I would stop processing the words on the page. When I would "break out of it" I would be able to remember exactly the movie scene that had been happening in my head, but I wouldn't be able to tell you the last few sentences I had read even though they perfectly described the scene I had been experiencing. This visualization of novels made me fall in love with reading as a kid.
I know you almost feel like 90% of the world got in on a huge psych joke a few years ago on a day we skipped class. Kinda of like that "dihydrogen monoxide found at 99% of crime scenes".
Idk if you know but Aphantasia technically covers all senses. For example I can hear music in my head. It's kinda faint and fuzzy but it's there and well defined. Meanwhile I can't imagine a simple green triangle. Maybe you have it in some ways and not others? You should think about it - kinda blew my mind.
Music definitely works differently in my imagination, but I notice that it also corresponds to very subtle breathing pattern changes. Like I'll be inhaling and exhaling with the beat and maybe very, very imperceptibly nano-humming. or perhaps I'm just _rationalizing_ the what-feels-like-nearly-physical music in my head by telling my lungs that they're helping to create it...
Maybe there's a similar vector I could explore for improved visualization. eye-movements or subtle pen-strokes with the hand or something.
For example when doing some shadowboxing I actually put fantasized people in front of myself which fight me and react to my moves, and I can see them as I see a real person until I remain focused. I often change also the location and the background to suite better my fantasy.
It's like shutting partially your eye system and making your mind go in full control.
edit: I said this to explain how much I can push it. But to make a simpler example, I _Very_ often fantasized at night, before bad and with eyes closed, of having an adventure in a post apocalyptic world and I can see everything in first person in my mind like I am really there and everything is real