'Changeling': VFX as 'Peripheral Imagery'

Changeling, the true life crime drama from director Clint Eastwood (now playing through Universal), does not make obvious use of visual effects, but wouldn't be the same movie without them.

Changeling stars Angelina Jolie as a single mother in 1928 Los Angeles whose nine-year-old son goes missing. When the police return to her a boy they claim is her son but she says it's not, it opens up a hot house of police corruption.

And that city is a major character in the film, brought to vintage life by Overall Visual Effects Supervisor Michael Owens working with CIS Vancouver and Pac Title.

Owens says the vfx work began with research into what the city was like in 1928 -- research of historical photographs and data that revealed the city had the most dense urban core in the world at the time.

Recreating that setting required shots what Owens describes as "peripheral imagery."

"We knew what we were getting ourselves into," he says. "It was 3D set extensions and Massive CG population. Cars, trucks, trains and street furniture -- that sort of thing," Owens adds.

Principal photography took place mostly on the back lot at Universal -- a location so well used in so many films that Owens felt it was important to mask familiar structures as much as possible. The back lot was mapped out with an eye toward figuring out where visual effects would begin and end in relation to the physical buildings.

Geoffrey Hancock, visual effects supervisor for the film at CIS Vancouver, says they created the right look using a collection of architectural elements from the era that could be recombined to create a variety of buildings."We changed out a lot buildings that were foreground-ish, midground-ish buildings just so that you couldn't recognize that stuff," he says.

"We could rearrange them and restack them to create either wider buildings or taller buildings of that same architectural style and then rearrange their order on the block so that you could create a very different looking city with only minor texture differences," Hancock explains.

Those decisions were based on vintage aerial photographs of downtown Los Angeles and tried to reflect the real geography of the city as a way to orient the audience in the story. "Having that consistency between scenes and shots we felt was going to help the audience get located and feel like they could understand the environment," he continues.

CIS used primarily Maya to animate and mental ray to render the city scenes, Hancock offers. A number of matte paintings were created using XSI and Maya, and some 2D work was done using Digital Fusion.

The project also called for extensive city crowd scenes, for which Owens says they turned to a combination of motion capture and the Massive crowd-generating software.

"We were planning to integrate Massive to a certain extent with live-action extras," Owens suggests. It was an ambitious task that presented its fair share of problems. "And up to the point where you're not mixing them, it works pretty darn well, because the Massive brain tells everybody where to go. But as soon as they started mixing around with the live action characters, then you have to encourage them to go one direction so you don't have to remove a live-action extra."

Actors were recorded with motion capture to get motions that matched the era. Owens says people tended to wear much more formal clothes, such as high heels for women and wool suits for men even in summer, and also moved in a more formal fashion.

The quintessential shot of this type is the final shot, which looks down a busy downtown street with City Hall in the distance while the head credits roll. Owens says he was the one who suggested the shot to Eastwood as a way to close the movie.

"I just thought it was a good idea to, before you leave the audience with those legends at the end, to not go to black too early," he says. "To just let them just emotionally take that in, and look at the imagery and let it out."

Lingering through the head credits means the shot lasts a good two-and-a-half minutes, during which people walk the streets, cars drive past and streetcars run up and down their tracks.

Owens says the shot began with live-action extras, which appear in about the first minute of the shot, and eventually goes to all-digital extras.

"Are there repeat characters? Yes," Owens says. "To me they look identical in that sense, but hopefully it's not obvious that that's what we did."

The shot also required CIS to lay in tracks and power lines for fake streetcars that ran on wheels, as well as add in some all-digital streetcars as well.

The shot's deep city receding into the distance pushed the limits of the polygons and texture sizes, Hancock says. Adding the Massive elements was a great opportunity, but made the shot even more complicated, as did the need to write shaders for the clothing.

To get it right, they did nearly twice as much MoCap as they had on previous projects. "We needed to actually capture that variety, to have the completely believability of the subtleties," he says.

Adding that believability to the Massive characters made it easier to integrate them into footage right next to live extras. "Once you could shade them and light them well and you knew that they were moving correctly, they fell into place and they could walk right next to another extra," Hancock says.

It also helped avoid some of the work they expected with cloth simulation. "We ended up using a collection of displacement maps in the air shader that were linked to the motion capture and would animate wrinkles in their wool pants and their stiff suit jackets," he adds.

The resulting shot was so long and had so many elements it required meticulous planning to ensure sufficient time to render it.

Another of Owens' favorite shots was from late in the film, when Jolie's character pulls up to the police station in a cab and walks inside. Owens says it was shot almost entirely against blue screen, with only a sidewalk, the cab and an extra. The final shot features the full gamut of effects on the film, including foreground Massive characters, set extensions and CG vehicles.

Owens says the end result met his standard for the look of the film. "Them standing right next to an extra is a pretty good way to tell if it's working or not," he insists. "I think (CIS) made a major leap forward for this project and I think that was to their credit."

CIS Vancouver, formerly known as Rainmaker, did about 90 shots for the film, with Mark Freund supervising the work at Pac Title, doing about the same number, with an emphasis on 2D shots, such as rig removal.

Owens first worked with Eastwood on Space Cowboys and says collaborating with the director has gotten easier as each has gotten to know the other's sensibilities and capabilities.

"Clint works very fast," Owens explains. "I just let him do what he does and keep track of what's going on and occasionally say, 'Can we do this instead?' But as time goes by, the more I can get used to what he's doing, the more I realize we can handle that and without visually compromising it."

One example is the use of rotoscoping, which Eastwood used in significant quantity on Flags of Our Fathers to avoid shooting blue screen for scenes atop the mountain.

"I realized that even though it's very expensive on the roto end, the lighting was way better," Owens says. With today's rotoscoping tools and artists practiced in the technique, it's become a reliable technique on Eastwood's films.

"Quite frankly, the technique makes shooting faster, easier and more natural -- and the end result is superior," Owens says. "It's always a big roto job, but you assume that right out of the gate and you're almost way ahead."

Thomas J. McLean is a freelance journalist whose articles have appeared in Variety, Below the Line, Animation Magazine and Publishers Weekly. He writes a comic book blog for Variety.com called Bags and Boards, and is the author of Mutant Cinema: The X-Men Trilogy from Comics to Screen, forthcoming from Sequart.com Books.