YouTube/Paramount/"Terminator Genisys"
The visual effects artists took months to get this sequence in "Terminator Genisys" right.
Like the previous films in the "Terminator" franchise, "Terminator Genisys" isn't stingy with its insane action sequences.
And one in particular goes out of its way to dazzle you as its filled with car crashes, a demolished school bus, and Arnold Schwarzenegger going through a windshield.
The scene happens in the middle of "Genisys," when an evil John Connor (Jason Clarke) chases after the Terminator (Schwarzenegger), Sarah Connor (Emilia Clarke), and Kyle Reese (Jai Courtney) through San Francisco.
The three are trying to evade John while driving a large school bus (it's a long story).
They all end up on the Golden Gate Bridge, leading to a showdown that won't go well for anyone traveling on the bridge. With Sarah behind the wheel of the bus, she swerves in all lanes of traffic, hitting cars as she tries to shake John off the bus.
The Terminator and Reese are in the back of the bus trying to locate where John is, leading to John throwing the Terminator off the bus; inevitably ending up head-first into a cop car's windshield.
YouTube/Paramount/"Terminator Genisys"
Before the bus falls off the bridge, the Terminator is able to pull Sarah and Reese to safety.
YouTube/Paramount/"Terminator Genisys"
The shoot did some practical stunts, including car crashes and the school bus rolling. But, like many action movies, the magic happened in post production when visual effects house, Double Negative, got their hands on it.
Oscar-winning VFX supervisor Pete Bebb of Double Negative had 30 people working on the sequence, which took months to complete following early test screenings in which Bebb got word that more had to be done to the scene.
"I think the scene started off originally as a relatively shorter sequence with less action," Bebb told Business Insider. "It turned out they wanted to flesh it out and have more crashes and cars turning over."
To create more chaos on the bridge and the feel that the audience is right there with the characters, Bebb and his team went to YouTube for inspiration.
"We didn't want to refer to other movies, so we just collected hundreds of clips from YouTube of dash cam videos of real car crashes," he said. "It sounds dark, but it gave the sequence a little more."
They were also responsible for making that 500-foot set of the bridge look like the real thing. That meant digitally increasing the speed of the bus and cars, giving more detail to what they shot on set (like the rolling bus) as well as extending the bridge digitally.
YouTube/Paramount/"Terminator Genisys"
Bebb said their work isn't just in front of computer screens. During production they went out to San Francisco and filmed every inch of the Golden Gate Bride to then use as background plates - the visuals they will put in back of the graphics they create.
But tweaking was needed to make what they shot look identical to what production did.
"Trying to attain day-lit vehicles is not as straight forward as people think," said Bebb. "The New Orleans sky was very bright while in San Francisco it was a bit darker. So it was a pretty big challenge to make it all match."
YouTube/Paramount/"Terminator Genisys"
"I think there's a preconception that it's computers so it's easy to fix but it's not," he said. "There's alway the line on set [to the VFX department], 'You guys can fix that, right?' Yes, we can, but it's a huge amount of work. We try to circumvent that by planning for a worse. We create everything with detail that's over and above what you think is required, just to make sure we're okay."
"Terminator Genisys" is currently playing in theaters.