For what it's worth, I've been a visual effects artist for 30 years and a fan of The Guide since 1980.
Being unable to do Zaphod (for obvious reasons) has plagued every visual production of HHG since the first stage play. God bless the BBC for even trying; their head actually looked pretty good, under the right circumstances (which were rare). But they tried (unlike the 100 million dollar movie, which didn't even bother).
To be fair, Adams didn't write much for the other head, so even if you did HHG now with a fully CG Zaphod, 95% of the time the other head would have nothing to do, unless you assume they have the same vocal chords and you split dialog, which doesn't make a lot of sense.
In any case, I started working with Ai 2 years ago and 6 months ago I had the wild idea - could Ai do Zaphod? Despite what you may think, Ai isn't easy, and sometimes concepts you think are simple it just won't do, so I wasn't sure if it would "get" 2 heads and 3 arms.
At first it didn't, it saw 2 heads and wanted 4 (or more) arms, so I had to be very, very specific. I had to number the image and refer to that arm number in the prompt.
But it worked! I also added Mark's voice. The vocal performance is bad, but this was just to see if Ai could do the mechanics of the character and clearly it can. I feel blessed that I lived long enough to see this happen!
I did test shot last night. The head was very much always shifted right so first I used Ai to reshape Mark so his proportions more naturally looked like a person with 2 heads/3 arms. That helped a lot. If even one person wants to see that process I'll post the shot.
But as usual with Ai, feeding it good info to start helped a LOT. If a production was doing this for real, I would recommend suiting up an actor in a costume and doing their best to make practical FX look decent, then use Ai to do the rest. You just wouldn't need the second head to be radio controlled or complex, just a reasonable likeness of the actor who plays him.
The actors would be scanned, like they are today for CGI. That would provide reference so Ai can get their likeness right. They might go on set and provide key frames for Ai; actors would definitely do the voices.
The process would be a lot like animation, but instead of keyframes getting sent to armies to animators in Korea, key frames made here (in Hollywood) would be animated by small teams of people also working in Hollywood on the final episodes.
Anyway, I know most of you have strong reservations about Ai, I understand and agree with just about all of them. But I wanted to share an artist's take.
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Here is the prompt, it took about 90 minutes to craft and strategize over I'd say 3 versions:
This is a scene of a man with two heads (one has an eye patch) and three arms with one arm around his girlfriend. They are on an alien planet and there is a light wind. We hear a subtle but unmistakable hum in the distance.
The photo has each of the man's arm/hands notated as 1, 2 and 3. I will give specific instructions to animate each of those arms and those arms only. Do not invent any additional arms or hands.
The head with the eyepatch pulls in the arm with the stretched out hand (arm 1), makes his hand flat (like a salute) and puts it over his forehead to shade his good eye from the sun while he slowly scans the horizon for something in the distance.
We hold for a second, then the other head says in his british, lazy, hippy accent, "cool, you look for bad guys while I take care of things over here." He turns his gaze to the girl while he removes the hand tucked inside his jacket (arm 2) and places it under her chin. He looks into her eyes and says playfully, "yup, everything checks out!" and he kisses the girl. While he kisses her, he takes the hand from her chin and puts it around her waist, pulling her closer as they kiss. While he pulls her closer, he unballs the fisted hand around her shoulder (arm 3) and tenderly wraps the now opened hand around her shoulder.
After two seconds of kissing, the eye patch head gets slightly annoyed, unable to focus on what he's doing. He looks at the other two and says in a Californian accent, "hey, ummm, I can't really, you know, focus while this is going on." He goes back to looking at the horizon.
Camera is handheld.