<em>Twilight</em>: A New Take on Vampire VFX

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Because the vfx team let the effects evolve on set without changing the director's documentary style, in Twilight [1] the goal was to get as many effects as possible in-camera. All images © Summit Ent. LLC. Courtesy of CIS Vancouver.

The teen-lit phenom Twilight has blazed its way to the screen with an opening box office bow of $69.6 million, courtesy of director Catherine Hardwicke (Thirteen) and Summit Ent. Based on the first of author Stephanie Meyer's quartet of books about a teenage vampire in love (which has sold a reported 17 million copies), Twilight has a large audience with built-in expectations about how it should unfold. And that applies to the visual effects as well as the love story between vampire Edward (Robert Pattinson) and his girlfriend Bella (Kristen Stewart). Because in Twilight, the vampires possess special abilities that have to be visualized -- they can race through treetops and hurl objects at impossible speeds. And when their skin is exposed to sunlight, they appear to sparkle with a thousand diamonds.

Visual Effects Supervisor Richard Kidd [2] recalls, "When I first came on the show, there were about 350 vfx shots planned. We thought that would grow to 500, but between early pre-production and when we actually started to shoot, we went down to about 95 shots. Of course, we knew it would grow back up again." Kidd, whose extensive credits include Armageddon, The Mummy, Transformers [3], Spider-Man 3 [4], Hancock [5], Cast Away and The Chronicles of Narnia: The Lion, the Witch & the Wardrobe [6], knew it was crucial to home in on the absolutely essential effects that reveal the vampires' powers. "There are only a certain percentage of shots you can do if you don't prepare."

"The director's focus was on the acting and the story," notes Kidd. "Catherine has a very documentary style -- sort of run and gun, which doesn't lend itself to visual effects. So my job in pre-pro and on set was to give her what she needed without changing her style. We just had to let it evolve. But at the same time, the idea was to plan in such a way that we could minimize the amount of visual effects shots. The whole process was to let them shoot this in such a way that we didn't end up with 500."

One strategy that made this possible was the pre-pro testing that Kidd conducted in L.A. before principal shooting began in Portland, Oregon. Kidd's goal was to try and get as many effects as possible in-camera. "So we actually shot for a number of days with a stunt unit on an exterior location near Lake Sherwood. Second Unit Director Andy Cheng and Second Unit DP Patrick Loungway and I tried a number of different techniques to make the vampires appear to run really fast and fly through the trees really quickly. We'd come up with some ideas, but we didn't know how well the stunt guys would be able to do them. One of those was what we called the 'magic carpet,' where we strung 15 pieces of 8-foot plexiglass that were pulled by a truck going 30mph. It was basically like an airport conveyor belt being pulled by a truck. So the stunt people would run on a surface that was also moving. But it's right near the ground so we could hide it as much as possible."

This had the effect of making the background trees appear to rush by especially fast, which sold the idea of the vampires' hyper-speed abilities. Kidd's team also experimented with variable film camera speeds to achieve different looks. "We figured out that a number of those techniques would work. We also shot tests with the Phantom HD camera, but we found that it wouldn't be usable in production for all the shots we needed."

All of Kidd's planning paid off during post for the digital visual effects team at CIS Vancouver, the main vendor on Twilight. "Richard was our man on the ground," says CIS Digital Effects Supervisor Geoffrey Hancock, a veteran supervisor whose credits include The Changeling [7], Vantage Point [8], Night at the Museum [9] and I, Robot [10]. "We'd had talks early on about things that we wanted to avoid, like moving branches. But Richard was able to get us all the information we needed."

Kidd recalls that while shooting the actors and stunt doubles on wires in the trees he tried to minimize anything that would present particularly difficult rotoscoping problems for the CIS team. "One of the things we came up against was that if we were moving the camera a lot we'd end up with trees behind trees multi-planing against each other -- and we'd also have a bunch of wires in the middle of that." Once those wires were removed, he notes, "CIS would have to replace infinitesimally small leaves. That made for some challenging rotos, but we tried to minimize that as much as possible while we were shooting so they didn't have very horrendous rotos."

In one signature shot of the protagonists in the trees, Kidd explains, "The stunt doubles were 100-plus feet up in a tree as we swoop around them and pull back. We needed to add a lot more trees to make the shot work. We didn't have the ability to turn this into a $100,000 shot by adding 3D-CG trees. And we weren't able to provide CIS with photographic elements of 100-foot-tall trees because we didn't have a helicopter to shoot elements. So, CIS came up with a way of creating 2D trees on cards that was cost-effective and also visually uncompromising."

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When VFX Supervisor Richard Kidd first came on the show, there were about 350 vfx shots planned. It expanded to 500, then went down to about 95 shots and wound up at 250.  [11]

Hancock adds, "We had a fun time with the helicopter shot around Edward and Bella perched in the top of the tree. It started off as a wire removal shot, and we used Digital Fusion to remove the wires. Then we needed to add some foreground trees and bushes to make it feel like the actors were out in the wilderness instead of on location in a 'groomed' field. It turned into a great example of the new 3D compositing features in Digital Fusion. We were able to do a 3D track of the swooping camera move and then -- just using images on moving cards -- creating the movement of tree branches, and layering many trees and having them stick into the ground. We could quickly make changes without having to go through the traditional 3D lighting and rendering and comping."

The shots where the vampires move through the trees serve to underscore author Meyers' idea that vampires are hunters, observes Kidd. "We did augment the traditional levels of motion blur with a bit of streaking to give the sense that they're moving impossibly fast. But it's not heavy-handed."

For a complex sequence in which the vampires play a baseball game, CIS helped Kidd prepare for the shoot by doing a Maya previs. The scene had to show the vampires' extraordinary abilities to throw and hit baseballs with lightning speed. These shots also required CIS to replace the skies with storm clouds and CG lightning -- major plot points for the storyline. As Kidd explains, "It's one of the scenes where the vampires could be themselves, because there's a storm rolling in, and with the thunder and lightning, the noise that they make when they hit the ball would be masked. They make a thunderclap sound because they hit the ball so strongly."

"The weather underwent a long evolution for this scene," notes Hancock. "In pre-production we wanted to get some thought put towards weather factors in case that would impact how the filming would be done. Initially they had an almost fantastical sky in mind with crazy formations of storm clouds, and then there was the push to get it in-camera and limit the horizon. That required that we see the sky through branches. We wanted to limit the sky replacements to more of the up-angle shots.

"The weather on the day of shooting was pretty cooperative," Hancock explains. "We extended our color correction as deep to the horizon as we could, but we had some rotoing of characters. In most cases were able to get far with color corrections to modify the existing sky in the plate behind the trees. This would leave the new stormier cloud elements above the treetops. Some of the shots did have animated rolling clouds but they were all approached from a 2D point of view -- there were some 3D tracks but mostly they were 2D cloud elements shot up here in cloudy Vancouver. We used Boujou for some of the complex 3D tracking -- for zooms or whip pans or really fast dollies. But a lot of it was just 2D tracking in Shake. It ended up being a moody scene with lightning and thunder, which provided a nice chance for visual effects to be part of the story."

Another aspect of preparation for the sequence was the gathering of environmental background images in case CIS would need to extend the background during post. As Kidd explains, "We shot gigapixel images for panning and tiling. We shot with a long lens and created enormous panoramas so that later if we needed a background we could zoom in on it at whatever level and have sufficient resolution. In the baseball sequence we actually did a full 360-degree view from the ground to the sky at extremely high resolution." This kind of home-made 2D 'Lidar', Kidd notes, "Allowed us to create lots of virtual set elements in 2D."

While it's become standard practice to add completely digital balls in sports sequences, Hancock had the idea of using clear plastic balls that the actors could actually hold, and then replace those later with CG. "When you ask actors to imagine having a CG ball in their hands you end up with hands that are too closed or too open, which means we have a lot of additional work to do manipulating fingers. We didn't have to contend with that because these actors had good solid objects that they could squeeze, rather than miming an imaginary ball." And having the balls be clear, adds Kidd, "Didn't affect the light nearly as much as if we had shot with a solid green ball. Also, if there were several cameras picking up close-up shots, we didn't want to have six baseballs out on the field that we'd have to paint out. In our wide shots we didn't have to paint out all those clear balls -- they'd kind of disappeared."

Orchestrating the varying speeds of the game's action was one of the most challenging aspects of the sequence, notes Kidd. "The baseball game was designed to show off the vampires' speed and jumping and running abilities. They could catch the baseball without gloves when it was traveling at 100mph. So we needed to do a lot of retimes in that sequence. We'd tried to anticipate where Catherine might want speed to be in the final cut, and then we'd shoot a multiple of that shot at high speed so we could preserve our options for later. That approach gave us more frames so we could do rampings in and out of the motions if during editing she decided to use a particular take that didn't have a high-speed alternate version. For example, we could generate new frames to ramp a 24fps shot to 48fps without looking jumpy." Hancock explains, "A lot of retiming work took advantage of Shake, Chronos and Twixter, which is a retiming plug-in that does a really good job of pixel motion estimation and frame interpolation."

The climactic fight sequence in Twilight was the most complex of all from a visual effects perspective, because it takes place in a ballet studio with mirrors on every wall and pillar in the room. The idea evoked director Orson Welles' famed hall-of-mirrors sequence in Lady from Shanghai, notes Kidd. To plan this sequence, he admits, "We spent a lot of time in prep. Not only was there a lot of wire work in the sequence, but Catherine wanted to shoot it with a lot of heavy atmosphere. Light beams were pouring into the studio at night, with the rest of the studio not being lit internally."

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The majority of vfx shots on Twilight were done at CIS Vancouver. ILM, Rez Illusion, Catalyst Media additionally contributed to the film.  [12]

To prepare for the shoot, CIS did a full Maya ray-traced previs, explains Hancock. "Because of all the mirrors, we wanted to try and anticipate how many times reflections were going to show up -- whether it was of the camera crew or repetitions of the actors' reflections. Because of Catherine's shoot-from-the-hip style, we were really looking for ways to anticipate problems. It wasn't so much figuring out angles -- we were looking for what was going to be the visual effects Gotchas."

Hancock notes, "The crew was really conscious of this. They had done some of their own tests and had come up with some interesting techniques for angling mirrors and frosting them to hide unwanted reflections." Kidd explains that during prep, they tried to troubleshoot potential problems with a variety of approaches. "If we put a couple of moving mirrors in front of the camera itself, would that save us? If we created a 'mirrored box' for that camera, would that minimize the number of crew reflections? What a lot of the people on the crew weren't thinking about was that there would be so many reflections between the crew and the actors that we might have a reflection that angles backward and then bounces off another wall and is actually seen behind the camera. That's why we did the previs."

When filming was completed, Hancock said, "Occasionally we'd find reflections of the crew and equipment. What was tricky was removing the wires. Many times we were removing wires up to 3 or 4 times deep. There were a lot of cases of long shadows being cast by the wires and it was tricky to get those plates clean."

The final tally of visual effects shots in Twilight turned out to be around 250, the majority of which were done at CIS Vancouver. Kidd explains, "As the show grew we ended up doing a few shots through other vendors. ILM did a half dozen shots, in which Edward is shown in sunlight and his skin appears to be encrusted with thousands of tiny diamonds. Rez Illusion did some of the speed ramp stuff and additional motion blurring of the vampires, and my company Catalyst Media, which operates as a four wall to get things done, did about three dozen shots. There were a couple where we did some 3D augmenting, but primarily we did 2D work." Kidd used Cinesync to work with the visual effects contributors to Twilight. "We used it with all the vendors -- even the ones in L.A. -- to communicate very quickly and go over all the different shots specifically."

With Summit moving forward with a Twilight sequel, New Moon, Kidd observes, "This movie is self-contained, but there could be a setup for a sequel, At this movie's conclusion, you know there's still some bad guys out there!"

Ellen Wolff is a southern California-based writer whose articles have appeared in other publications, including Daily Variety, Millimeter, Animation Magazine, Video Systems and the website CreativePlanet.com. Her areas of special interest are computer animation and digital visual effects.