LOS ANGELES – Petro Vlahos, a two-time Academy Award winner whose blue- and green-screen technique on movies like “Mary Poppins” and “Ben Hur” made the modern blockbuster possible, has died. He was 96.

The night before his death Feb. 10, he was on the minds of many at the Scientific and Technical Oscars ceremony, where he’d been a constant presence through the years and where his acolytes won most of the trophies.

“He created the whole of composite photography as we know it at this time,” visual effects supervisor and one of the night’s top winners Bill Taylor said, drawing a line from his early work to recent technical marvels like “Life of Pi.” “Whenever you see Mary Poppins dancing with penguins, when you see Pi in a boat in the middle of the ocean … you are seeing … Vlahos’ genius at work.”

Others had tried “composite photography” before, combining separately filmed actors and sets into one shot, but results had been spotty, and actors often appeared with a halo of light around them.

Vlahos took huge leaps forward with the chariot race in the 1959 Charlton Heston epic “Ben Hur” and in Julie Andrews’ and Dick Van Dyke’s romp through a chalk-drawing wonderland in 1964’s “Mary Poppins.”

He kept up his partnership with Disney in effects-heavy films like 1969’s “The Love Bug” and 1971’s “Bedknobs and Broomsticks.”

When in subsequent decades sci-fi and fantasy films became dominant at the box office, Vlahos’ techniques became dominant in filmmaking, essential to movies like “Avatar” and to every film in the “Star Wars” saga.

He and his collaborators won an Oscar for their composite processes in 1965, and he and his son Paul Vlahos shared another Oscar in 1995 for the blue-screen advances made by Ultimatte.