The filmmakers of Rogue One faced particularly tough challenges — they needed Grand Moff Tarkin and Princess Leia Organa. Peter Cushing, who played Tarkin in Star Wars, died in 1994; Carrie Fisher, who portrayed Princess Leia, was still alive during the making of Rogue One, but looked and sounded nothing like she had in 1977. Thus, Tarkin and Leia were digitally recreated.
For principal photography, Tarkin was played by British actor Guy Henry, who wore a motion-capture headpiece. John Knoll, chief creative officer at Industrial Light & Magic, told the New York Times the filmmakers had back-up plans in case their digital Tarkin didn’t make the grade, admitting, “We did talk about Tarkin participating in conversations via hologram, or transferring that dialogue to other characters.”
Not quite so much work was needed for the digital rebirth of Princess Leia. When seen from behind, she’s fully Norwegian actress Ingvild Delia. From the front, what you see is almost entirely a digital creation, though Leia’s outstretched hand is Delia’s.