PARK CITY, Utah - The talking heads in some documentaries at the Sundance Film Festival are not just real people recollecting real events.

Some are actors, recruited by the directors to help put human faces and voices to events lost in time, for which the filmmakers would have had to rely on static old photographs or artist sketches accompanied by narration to relate a story for which no video record exists.

The opening-night film Thursday at the 11-day festival, "Chicago 10," uses a voice cast including Nick Nolte, Roy Scheider, Mark Ruffalo, Jeffrey Wright, Liev Schreiber and Hank Azaria for clever animated sequences that recreate the bedlam of the trial of anti-war demonstrators accused of inciting violence at the 1968 Democratic National Convention.

"Nanking," a study of the brutal Japanese occupation of the Chinese city in 1937, employs powerful performances by Woody Harrelson, Mariel Hemingway and others reciting from letters, journals and other accounts of people who lived through the invasion.

"Strange Culture" features Tilda Swinton, Thomas Jay Ryan and other actors in dramatized segments of events that led to the arrest of a University of Buffalo professor on suspicion of bioterrorism.

"Chicago 10" director Brett Morgen had endless archival footage of street protests and defendants such as Jerry Rubin and Abbie Hoffman discussing the events in public. What he lacked was a way to incorporate the trial, until he came across a comment from Rubin that the courtroom saga was a cartoon show.

"A lightbulb went off that if we animated the trial, it's not only making a subtle comment about the proceedings, but it would allow me to have the characters look exactly like the characters in the archival footage and create a seamless transition," Morgen said.

Using actors to help re-enact events is nothing new to documentarians. But in the latest Sundance documentaries, filmmakers are engaging performers to add an emotional depth that dusty photos and third-person narration might lack.

"Nanking" directors Bill Gutentag and Dan Sturman became fascinated with the heroics of American and German missionaries, doctors and businessmen who used the U.S. flag and the Nazi arm band to shield huge numbers of Chinese in a safe zone when the Japanese took over the city.

"What we were looking for was an involving way of telling what we think is a very powerful story about these Westerners who saved hundreds of thousands of people," Gutentag said. "But there's virtually no footage on them. No interviews, no film on them. But they left behind an amazing amount of work."

Gutentag and Sturman wove readings by Harrelson, Hemingway and the other actors almost like a stage play through the more traditional documentary parts of "Nanking," which include present-day interviews with survivors of the Japanese occupation.

"The pure narration of these real people gives it some heart and some soul," Hemingway said. "When you use actors, you really connect with the character. You get the feeling of really going through the event."

In the case of "Strange Culture," director Lynn Hershman Leeson had to find a creative way to tell parts of college professor Steve Kurtz's story because he was under federal indictment, his lawyers limiting what he could say on camera for legal reasons.

Kurtz's ordeal began after his wife died of natural causes. Emergency officials who came to their Buffalo home grew suspicious of the biological supplies he had for a planned art exhibit on genetically altered foods, and federal agents detained him on suspicion of terrorism.

While Kurtz provided extensive interviews for "Strange Culture," events just before and after his wife's death are dramatized, Ryan playing Kurtz, Swinton his spouse.

The dramatizations provide an unusual window that helps viewers connect with the story, Leeson said.

"I think there's a sense of immediacy, for one thing. You have the drama, but you have what's behind the drama," Leeson said. "This gives you a different kind of interpretation of what truth is. Truth is not just one omniscient voice, one omniscient character that says everything."