"The Holocaust is well documented, and we have confessions of the major war criminals," he said. "But there's nothing like the human witness who can look you in the eye and say, 'Look, this is what happened to my husband. This is what happened to my children. This is what happened to my grandparents.' "
Developing a technology capable of that has been painstakingly time consuming. But in the past two years, researchers say, it has come together faster than they once imagined.
To help in the effort, Gutter had to sit under an array of hot stage lights and in front of a green screen for hours at a time over the course of five days, answering some 500 questions about himself and his experiences.
Research scientists at USC are still editing them and working with voice-recognition software so that his hologram will not only be able to tell his story but recognize questions and answer them succinctly. Being able to do that often required asking as many as 50 follow-up questions to one of the original ones, Smith said.
While researchers have found there is generally a range of about 100 questions people ask survivors of the Holocaust, if someone in the future comes up with one Gutter's hologram can't answer, it will simply say so and refer them to someone who might know.
For the demonstration shown this week, he sat before seven cameras. For the final hologram, more than 20 will be placed at every angle possible, so he will appear to people standing or sitting anywhere in the audience just as he would if he was really there.
No pepper screen will be used to display his hologram, as was the case with Shakur. Instead, it will be broadcast into open space, allowing people to approach and interact with the hologram just as they would a real person.
Eventually, according to Debevec and other researchers, holograms could come to have numerous uses. Among them would be teaching classes, taking part in business conferences and providing expert opinion on subjects when real people can't be there to do so. They could even be used as teaching tools for people studying to become therapists who aren't quite ready to work with a real, emotionally troubled person.
For now, however, researchers are working strictly with Holocaust survivors, creating a list of nine other people with the help of the private group Conscience Display, which records survivors' stories and suggested the project.
Given that every person interviewed has been 80 or older, Smith said, it may prove difficult to find subjects with the stamina to participate. Still, no one approached so far has said no to the idea.
Perhaps Gutter's digital presence summed up the reason for that best when it was asked the other day why he chose to take part.
It replied: "I tell my story for the purpose of improving humanity."
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