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For wild chase scenes, it’s hard to beat Doctor Strange. In this 2016 film, the fictional doctor-turned-sorcerer has to stop villains who want to destroy reality. To further complicate matters, the evildoers have unusual powers of their own.

“The bad guys in the film have the power to reshape the world around them,” explains Alexis Wajsbrot. He’s a film director who lives in Paris, France. But for Doctor Strange, Wajsbrot instead served as the film’s visual-effects artist.

Those bad guys make ordinary objects move and change forms. Bringing this to the big screen makes for chases that are spectacular to watch. City blocks and streets appear and disappear around the fighting foes. Adversaries clash in what’s called the “mirror dimension” — a place where the laws of nature don’t apply. Forget gravity: Skyscrapers twist and then split. Waves ripple across walls, knocking people sideways and up. At times, multiple copies of the entire city seem to appear at once, but at different sizes. And sometimes they’re upside down or overlapping.

Bringing the twisty other world of Doctor Strange to the big screen required time, effort and computers. Wajsbrot also needed a geometric pattern called the Mandelbrot (MAN-del-broat) Set. This is a type of shape known as a fractal. It’s made of curves and patterns, but those curves and patterns have curves and patterns of their own. There are patterns within patterns. And similar ones show up as you zoom in on an object. This happens in nature, too. Zoom in on a jagged mountain top and you find smaller jagged peaks within the peaks.

The Mandelbrot Set is a pattern called a fractal. It looks a little like a bug. Look around the edges, and you can see smaller Mandelbrot “bugs.” If you could zoom in on those bugs, you’d find still smaller copies.

CREDIT: WOLFGANG BEYER/WIKIMEDIA COMMONS (CC BY-SA 3.0)

The people who worked on special effects for Doctor Strange wanted to use a lot of fractals, says Wajsbrot, who works with a company called Framestore. As characters try to navigate bizarre changes to their reality, scenes zoom in or out on a building, wall or floor. And this reveals more buildings, walls and floors within. The filmmakers’ goal was to use math to create sights that people had never seen in a movie before. To get that type of novelty, Wajsbrot says, they needed fractals. And of all the fractals they worked with, they found special inspiration in one type — the Mandelbrot Set.

“The Mandelbrot Set,” says Wajsbrot, “was the cherry on the cake.”

How math makes movies like Doctor Strange so otherworldly

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