Platt died Wednesday of Lou Gehrig's disease at her home in Brooklyn, N.Y., according to her daughter, Antonia Bogdanovich.
"She worked on important pictures and made major contributions," Bogdanovich told The Times on Wednesday. "She was unique. There weren't many women doing that kind of work at that time, particularly not one as well versed as she was. She knew all the departments, on a workmanlike basis, as opposed to most producers who just know things in theory."
Platt had an extended collaboration with writer-director-producer James L. Brooks, serving as executive vice president of his production company, Gracie Films, and producing "Broadcast News," "Say Anything," "War of the Roses" and director Wes Anderson's first feature film, "Bottle Rocket." She was also instrumental in bringing Matt Groening, the creator of "The Simpsons," to Gracie Films when she saw his comic strip "Life in Hell."
"She couldn't walk into a gas station and get gas without mentoring somebody," Brooks said Wednesday. "Movies are a team sport, and she made teams function. She would assume a maternal role in terms of really being there. The film was everything, and ego just didn't exist."
Platt received an Academy Award nomination for best art direction for Brooks' 1983 film, "Terms of Endearment."
Among the directors she worked with, Platt was known for her peerless taste and frank demeanor. "I used to be afraid in meetings with executives that she would snort with derision if she heard something she didn't like," Brooks said.
Born Jan. 29, 1939, in Fort Sheridan, Ill., to John Platt, an Army colonel, and Vivian Marr Platt, an ad executive, she moved to Germany with her family at age 6, when her father served as a judge at the Dachau trials of Nazi war criminals.
Living in Europe as a child influenced Platt's attitude and her aesthetic sensibilities, according to her daughter, Antonia.
"It made her tough, what she saw there," Antonia said. "Her talent in production design came from her absolutely exquisite taste, and she developed a lot of that taste living in Europe."
Platt studied art at what is now Carnegie Mellon University in Pittsburgh and then moved to New York, where she worked in summer stock and met Bogdanovich.
The marriage fell apart during the filming of "The Last Picture Show," when Bogdanovich left her for the movie's star, Cybill Shepherd, but the two continued to work together on the films "Paper Moon" and "What's Up Doc?"
When she died, Platt was at work on a documentary about low-budget movie producer and director Roger Corman, and had just finished writing a memoir, according to Antonia.
Platt is survived by her brother Jack Platt and her two daughters, Antonia Bogdanovich and Sashy Bogdanovich, and three grandsons. She also leaves behind two stepchildren, Kelly Wade and John Wade, from her marriage to prop master Tony Wade. He preceded her in death.