The apartment set was built full of light strips, and Deakins either used these practical lights to light the actors, or used the practical lights to motivate the master lighting.
The set itself was tight and did not allow a lot of room to work.
The character Joi is supposedly named after the urban slang porn acronym for J. I : Jerk Off Instruction, which is a tease game between a porn actress and the camera/viewer. In her first scene, Joi shifts roles (and outfits) rapidly from attentive and warm confidant, to coy seductress.
It is only later in that scene that it is made clear to the audience that Joi is a cognitive virtual human hologram, and the only meaningful relationship in K's harsh life.
Of all these early tests, which ranged from wireframes to particle systems, the only one that seemed to have promise for the story they were telling, was a simple 2D comp with a partial Screen transfer function.
This semi transparent, subtle look, while not enough, was preferred to more elaborate and intrusive effects.
The film establishes that, while Joi appears solid, she is actually some type of light projection with no solid matter and people can pass through her without resistance.
She demonstrates this being on either side of K, passing through him at the data repository while he looks at the archives.
The film's production visual effects supervisor was John Nelson and this sequence was handled by Double Negative, with Paul Lambert as DNeg's Supervisor.Paul Lambert saw Joi as either being re-programmed or grown beyond her programming to be so much more than just a sex companion.It was therefore very important for the audience to connect with her and care about her.Much as one would see the back of a wine bottle's label if you sliced the bottle directly in half.And like a wine bottle this is only visible as the bottle is made of transparent glass.(This particular scene at the archives was done by Framestore, based on the same approach that DNeg used).Joi who seems to 'genuinely' care for K, hires a replicant sex worker Mariette.Second, a 3D version of Ana de Armas as Joi was made from extensive scanning of the actress and a face scan from USC ICT.This 3D model was then importantly cut vertically in half.But as Samantha is never visualised as a face or presence, and remains just a voice, no visual effects were required for that sequence in .To understand how the sex scene was achieved we need to look at how Joi was introduced into the film.