Petro Vlahos, a special-effects pioneer who developed the blue-screen and green-screen process that allowed Dick Van Dyke to dance with penguins in “Mary Poppins,” the blue-skinned Na’vi to live among floating mountains in “Avatar,” and TV weather reporters to point at sun and rain symbols that only their viewers can see, died on Feb. 10 in Los Angeles. He was 96.

His death was announced by Ultimatte, the company that he and his son, Paul, founded in 1976.

The technology Mr. Vlahos perfected, earning him Oscar and Emmy awards, creates the illusion that actors or settings filmed separately are in the same place. It has made it possible for young actors to play their own twins and share scenes with them; for princesses in galaxies far, far away to send hologram messages; and for nonexistent, distant worlds and their wildlife to appear real in convincing detail.

“His inventions made a whole genre of film possible — a genre that seems to make more money than any other,” said the visual-effects supervisor Bill Taylor, speaking at an Academy of Motion Picture Arts and Sciences event the day before Mr. Vlahos died. “He created the whole of composite photography as we know it.”

In an interview with the BBC, Robin Shenfield, president of the Mill, a British visual-effects studio, summarized Mr. Vlahos’s contribution and talent as “that fundamental ability to take lots of elements from lots of places and seamlessly mesh them,” creating “a new convincing reality.”