Bad Cold Breath: A Special Effects Expert Speaks

Slate's Culture Blog
Jan. 18 2011 3:15 PM

Bad Cold Breath: A Special Effects Expert Speaks

Last week, we pondered


a distracting hobgoblin in an otherwiseexcellent-looking film. We wondered: Why are shivery puffs




They're not really, says John Clark, a visual effectssupervisor at Sony Pictures Imageworks and instructor at The GnomonWorkshop . It just depends on how much time and money you have. Quick, cheapset-ups make for cheap-looking clouds as evidenced by any number of YouTube hobbyistvideos

You can model cold-breath vapor particles in two dimensionsor three, but the best-looking results come with the latter. "Generally, the 2Dapproach doesn't look as realistic," Clark says. "The particles are notactually moving in a Z-direction, they're not moving towards the camera. Itlooks acceptable, but it's not necessarily moving in a real volumetric way." But3D models take more time to set up particularly if you're using a sophisticated fluid simulator andthe refining process can be way more expensive and labor-intensive.

Another challenge to making good-looking breath clouds is that(unlike ten-foot-tallaliens ) people have seen them plenty of times before. "You know how itmoves, and how the particles linger and how they disperse," Clark says. "It'svery easy for the eye to get distracted if it's not behaving exactly right."

In the case of TheSocial Network , the fog coming out of Jesse Eisenberg's and AndrewGarfield's mouths probably looks off because it's overdone. "If you observe real 'cold breath,'" Clarkwrote in an email to Brow Beat, "it is very transparent, almost invisible untilyou shine light through it, and does not form when people speak small wordsthat require only a tiny bit of air."

Meanwhile,unobtrusive, lifelike vapor breath is more common than you might think. Clarknotes that pretty much any film taking place in a consistently snowy locationis likely to have used the effect. If the movie was shot on a sound stage withfake snow, the breath is obviously going to be simulated. But even on locationshoots, weather conditions can shift as the day progresses the actors' breathcould be visible in the morning and gone by noon, requiring the addition ofcomputer-generated puffs.

Clip from The Social Network © Columbia Pictures 2011. All rights reserved.




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