Timo, wasn't there a holographic recording displayed in one of the trek movies? Of the Klingon Chancellor?
Ah, right. Except it was vice versa - Chancellor Azetbur was on a viewscreen in Paris, while President Ra-Ghoratreii was a hologram above Azetbur's desk in First City or whatever.
Yistaan, holographic displays were used at least once in the first season of TNG. I seem to recall either Data or Geordi using them (over a table - maybe in the Ready room?) to show a 3-D visual of something they'd encountered.
The Tkon Empire in "The Last Outpost" was discussed with the help of a projection above the Observation Lounge table; the biocontainers of "The Child" were shown in holographic form in the Ready Room; Riker had holographic soft porn figures in his cabin; Data and Kolrami played a holographic game in Ten Forward; Worf selected a wedding present for Miles and Keiko using a holographic catalogue; etc.
Holoprojections were a more or less constant presence in Star Trek from "Encounter at Farpoint" to "Endgame". It's just that towards the later spinoff seasons, they were more confined to the holodecks than in the early years.
Lastly, I read on another forum the theory that they are still and have always technically been using holographic images for comms (in TNG for example), but no-one noticed.
Oh, yes, the communications screens were 3D up until DS9 when they started using actual monitors instead of faking it with VFX.
From an end-user perspective, I don't see what the advantage of holographic ship-to-ship communications (to make it look like the person is standing there in the room with you) would be over using the viewscreen.
I gather the idea would simply be that "you are there". Instead of being a disembodied voice, you actually stand right next to these other folks, so the interaction goes to the next level. It's an advantage over the disembodied voice the same way a telegram is an advantage over a letter or a video conference is an advantage over a phone call - but it's basically the
ultimate advantage, transforming "communications by means" into plain being there. It's difficult to see how things could be improved upon (DS9 style solid) holocomms even in theory.
In any case, it's imperative that you appear in full body form, visually convincingly, and completely without your real surroundings, or else you aren't there. The tech in DS9 managed this; the tech in DSC has so far been visually coarse enough that the illusion is broken, even though holograms that are
not long range communications can be made visually perfect.
Timo Saloniemi