In an old National Lampoon cartoon, a moviegoer exiting a theater enthused: “Well, I couldn’t really say if the movie was a good one or a bad one, but the illusion of motion created by what was really nothing more than the rapid projection of a succession of still images was itself worth the price of admission!”

People have been fascinated by that illusion of motion ever since Edweard Muybridge went to see a man about a horse over a hundred years ago. In his now famous wager, Muybridge set up an array of cameras to see whether or not the animal’s feet all left the ground at the same time during a gallop. The running horse tripped wires that, in turn, activated the cameras, proving that it did in fact become fully airborne. Modern filmmakers have updated this classic methodology. By triggering an array of still cameras simultaneously, and projecting the resulting images sequentially in motion picture form, visual effects wizards have created a technique in which a moment in time is frozen while the apparent taking camera continues to dolly past or around the subject. The captivating illusion, seen first in music videos and TV commercials in the mid-nineties, gained wide-spread prominence as the centerpiece effect in The Matrix. Gale Anne Hurd, producer of such high-octane effects films as Aliens, The Abyss and Armageddon, saw a terrific opportunity to take that technique to the extreme with Clockstoppers, a science fiction adventure aimed at teen audiences.

In Clockstoppers, a high-tech wristwatch possesses the ability to accelerate molecules to the point where the bearer, or anyone touching him or her, enters a state of ‘hypertime.’ The prototype invention’s potential for mischief, which ranges from teenage pranks to capital crimes, makes it a coveted object. High-jinks follow as the watch passes from its brilliant, but eccentric, creator Earl Dopler, to Dopler’s former professor George Gibbs, to Gibbs’ teenage son Zak and Zak’s girlfriend Francesca. “My first reaction to the original spec script by Rob Hedden,” recalled Hurd, “was that if I were a kid, this is exactly the sort of premise I would be drawn to — the ‘what if?’ scenario, especially since there is an element of wish fulfillment. The kids in the story take technology and have fun with it; but they realize that there is a darker edge to it. Something that they see as a device to be used for fun could actually have sinister purposes if it fell into the wrong hands.”

To shoot the effects-heavy show on a tight, fifty-three-day schedule, Hurd chose actor/director Jonathan Frakes, who had successfully helmed the two most recent Star Trek features. “It was wonderful having Jonathan as director of this film,” noted Hurd, “because nothing frightened him, and he also didn’t have the hubris to believe that the postproduction process is a big black box where anything you screw up in production can be fixed. So we were on the same page all the way through the show. We both knew what we could accomplish and what was beyond the bounds of our time and money.” Hurd and Frakes turned over Clockstoppers’ 200-shot effects slate to visual effects supervisor Michael Fink, a former freelancer who had recently signed on at Cinesite, where the bulk of the show’s digital effects work would be undertaken. Two other companies provided additional effects support — Pacific Title Digital, which was assigned some 3D computer animation along with routine wire removal and compositing for twelve shots, and Reel EFX, which provided its Multicam equipment for an important camera array shot.

Planning how to visually convey the film’s central premise of hypertime was an essential early task. “We had huge, hours-long conversations,” Fink recalled, “where we would talk about the sequences and formulate a concept of what hypertime was and what it meant. Based on that, visual effects supervisor Jackie Lopez created a document called ‘The Rules of Hypertime.’ Actually the discussions never stopped, because as we shot the movie, Jonathan would have an idea or I would have an idea, and one of us would always say, ‘Well, doesn’t that violate the rules of hypertime?’ Then we’d come up with some great, logical explanation as to why it didn’t, and why we should proceed.”

Among the rules of hypertime established by the filmmakers were those stipulating what audiences would see depending on the point of view being depicted. For instance, it was determined that the molecules of a person in hypertime, seen from the point of view of someone in normal time, would be moving at such an accelerated state as to render him invisible. From the point of view of someone in hypertime, however, anyone or anything that was not in direct contact with him — and therefore not in an accelerated state — would essentially appear frozen in space. “The rule of thumb was that we didn’t want people to be really stopped dead,” explained Fink. “We wanted a little bit of motion in everything, just to keep it alive – which makes everything quite a bit harder to do, but certainly looks more interesting.”

Given its pervasive use of the hypertime perspective, action scenes with characters moving in and out of hypertime at dizzying speeds, and a climax in which Zak is catapulted into an even more extreme state of acceleration known as hyper-hypertime, the Clockstoppers story would be a difficult one to tell. “To keep all of it straight,” remarked Fink, “we really had to obey the rules we set up. The problem was that in order to make the movie possible within a somewhat limited budget, we had to cheat on a number of the frozen-time shots – using mimes or having people standing very still as the camera went past them – making those people appear really static. So we pulled back from the level of motion we thought we were going to be depicting to an even lower level of motion, to the point where people actually do look frozen, and you don’t see much motion at all, unless you know it’s there.”

Extensive testing conducted before the start of filming helped to pin down shooting strategies for the frozen-time shots. “We shot tests with people walking, running, dancing, bouncing on trampolines, tests with automobiles, day and night tests – all of this to see where the techniques would fall apart,” recalled Fink, “because on a fifty-three day schedule, we didn’t have time to make mistakes in shooting these shots. The testing accomplished two things – it helped us choose techniques, and it helped Jonathan figure out how he wanted to tell the story.

“In terms of camera technique, we found that if the camera was dollying or moving in a circle around people, we could have the subjects move a little; and even if they were not moving smoothly, the camera motion would take out a lot of the jitter and make it feel like a natural frozen position. So there are a lot of shots in the movie where the camera is a Steadicam that goes around or through a group of people, so that you get the feel of some dynamic motion from the group, even though you really can’t see it.”

Other tests entailed digital manipulation of footage in the compositing stage to slow the apparent speed of a filmed subject. “We shot a test in a number of environments, from 24 frames all the way up to 360 frames per second,” said Fink, “then used our in-house software, Cinespeed, to slow it down. We took 24 frames and slowed that down to about 2000 frames, and 60 frames and slowed that down to 10,000 frames to see what we could get away with before it fell apart.” In the end, although some things were shot high-speed, most shots would rely on speed changes done in compositing, and just one sequence at the end of the film would be relegated to the still array camera technique.

The hypertime perspective is first established through Zak (Jesse Bradford), who pockets the mysterious watch after discovering it in his father’s basement lab. Unaware of its powers, Zak unwittingly sets the watch timer in motion while raking leaves in the yard of would-be girlfriend Francesca (Paula Garces), and is instantly propelled into hypertime. Spotting what he believes to be a dead possum, stiff with rigor mortis, Zak carries the carcass into Francesca’s kitchen, eager to show off his catch. To his surprise, he finds Francesca frozen in the act of fetching drinks from the refrigerator. Walking around her, Zak waves his hand in front of Francesca’s face with no reaction. Suddenly, the timer runs out and the watch jolts him back into real time, as everything in the room – including the possum — comes back to life. Startled and angry that Zak would bring a live possum into her kitchen, Francesca sprays the presumed prankster with a kitchen sink hose. Ducking to avoid getting doused, Zak activates the watch by accident, and everything — including the arcing stream of water — freezes again.

Though Fink knew from his earlier testing that under many conditions, pantomime would suffice in capturing frozen time characters — provided a camera move masked imperfections in the pantomimed performance – he opted to use motion control for the kitchen sequence, guaranteed to deliver results. Cinesite previsualization supervisor Andrew Honacker was called upon to work out the logistics of the live-action camera move. “The shot went through a bunch of incarnations,” stated Honacker, “because we didn’t know if it was going to be filmed on a set or a location. We knew it was going to take three or four passes of the motion control camera, with different things going on, to get what we wanted. But each location that we looked at had certain limitations as to where the rig could be set up and what it could do. Also, this one effects shot was right smack in the middle of a rather lengthy sequence; and if things weren’t set up properly during the live-action shoot as to where characters and objects were placed, there was going to be a mismatch in continuity.”

Ultimately, the scene was filmed in the kitchen of a real house, in the Silver Lake district of Los Angeles, over the course of a week-long shoot. “We started by blocking out how we wanted the shot to feel,” Honacker recalled, “how close we were going to get to the kitchen sink water sprayer, how fast it was going to be, how quickly Zak was going to walk around Francesca, and how far down we were going to start. Originally, we had a much bigger move planned, but that had to be scaled down to accommodate the kitchen, which was quite small.”

Although the effects crew planned to shoot the move — about twelve seconds long in real time — at the standard 24 frames per second for Zak’s portion of the action, the plan was to use a much higher frame-rate to depict Francesca slowed down to a near stop. “The human body can hold still to a certain extent,” noted Honacker, “but there’s always going to be just a little bit of movement, a twitch here and there. In order to smooth out any problems like that, we wanted to shoot Francesca at 72 or 96 frames per second. To do that, the rig had to move three to four times faster, so this thing was going to have to whip around to get the shot.”

Tests conducted prior to shooting produced surprising results. “We set up the rig to do a very rough move based on some earlier previz we had done,” recalled Honacker. “After shooting some footage for the real-time pass, we started cranking the system faster and faster to try and push its limits. We got to a point where it was doing 48 frames per second fairly well, completing the move in six seconds. Then we went for a 72-frame pass, which essentially meant that the rig had to make its move in four seconds. When it got to the end of the eighteen-foot track, it suddenly lurched, started to shake, made this horrifying noise and just went nuts. The camera assistant and the grip chased after and the mo-co operator slammed the emergency stop button over and over and over. Fortunately, at the end of the track the emergency stop kicked in and all power to it died. But the rig still had momentum, so it hit the bumpers and just leaned over with these two guys holding onto it to keep it from toppling.”

As a result of the test, Fink had to rethink his shooting strategy. “Though we had expected that at some point the system would go out of control,” remarked Fink, “we were surprised at how soon we hit that point. So we modified our approach. We let the camera remain in the same path we had originally planned, but since there are a lot of ways to move the underlying support structure and still preserve the same camera path, we found a new way to compensate for the interaction between the dolly move and the arm swing in the motion control system that would be physically achievable at 72 frames per second.” Camera crews experienced additional problems during the actual live-action shoot when a power spike in the Silver Lake house damaged the motion control system computers shortly after shooting got underway. Facing a tough call in terms of whether to delay production with additional shooting, or to use the passes already filmed that included both actors at 24 frames per second, Fink determined that Paula Garces’ performance at 24 frames per second would hold up sufficiently in the final shot, and decided to forego additional shooting.

A Cinesite team led by CG supervisor David Altenau added 3D animated frozen water droplets arcing from the kitchen sprayer. To simulate the refraction of the background plate photography in the CG water, artists ran in-house software to render out a field of per-pixel motion vectors for each frame. “We used that data to displace the background plate,” said Altenau. “In other words, the animated foreground water element became a distortion pass. It was quite a neat little tool.” Computer animators grossly tracked the arcing 3D water element to the live-action plate using 3D-Equalizer. Precise in-house 2D tracking solutions took them the rest of the way, locking the origin of the CG spray to the nozzle in Francesca’s hand. The final shot was assembled by compositing supervisor Jason Piccioni and his department.

Cinesite also added a digital effect, dubbed a ‘warble,’ to the shot of Zak initially being jolted into hypertime. The transitional effect – mandated by Frakes as a means of telegraphing to audiences when a character was entering or exiting hypertime — would be repeated many times throughout the show. “What we wanted with the warble,” explained Fink, “was some sense of a temporal shift. I wanted it to feel like parts of Zak were speeding up while other parts weren’t quite there yet, and there was a bit of a lag as the other parts were catching up. So we used a fairly old-fashioned technique we call ‘latency.’ We took the image and used our Cinespeed software to streak it as if it were a slitscan shot. It kept the leading edge fairly well-defined, while the trailing edge became a smear, with the back-end coming in sharp again. We had a lot of control over how we warped that, how we distorted and stretched it; so it could be very staccato and nasty-looking or really smooth.”

To add visual interest to the warble effect, Fink also came up with the idea of having the camera punch in to its subject and spin around him, pulling back out to reveal a slowed-down world. “We’d shoot Jesse, or Jesse and others in front of a greenscreen doing their action, then stepping onto a motorized turntable, built by Gary Monak, which rotated slowly while the actors held fairly still,” observed Jason Piccioni. “For the background, we usually just tiled stills together. We took it all into composite-land, sped up his spin and gave him a bit of the latency effect so that part of his faced ripped apart, then held together when it caught up with itself.”

The element that worked to the greatest comic effect in the kitchen sequence – a shot of the possum coming back to life as Zak abruptly exits hypertime-proved the easiest to achieve. Filmmakers relied on a simple trick, using a prop possum in one shot, and substituting the prop with a real possum for a following shot of Zak dropping the startled, suddenly revived animal. The transition between the two shots occurred across a cut, and image warping of the prop possum’s head by Cinesite contributed to the apparently miraculous revival.

Having discovered that two people may occupy hypertime as long as they are in contact with each other when the watch’s timer is pressed, Zak and Francesca activate the watch and venture into the backyard. There they encounter a world of natural wonders – all seemingly suspended in mid-action. “Zak and Francesca are just discovering hypertime,” observed Altenau, “so we needed a ‘wow’ sequence that really presented some beautiful images that would be stunning and fun to watch, and where you could really get into the characters’ heads and just be blown away by how cool hypertime is as you see it from their POV. We threw everything at those shots. We have doves that are quite close to the camera and just barely moving. Next, the camera pans off a sprinkler, which is across the yard. Then we see a hummingbird.”

Frakes purposely zeroed in on bees and hummingbirds to sell the premise of hypertime. “Bees and hummingbirds move very rapidly, so they really help convey the idea that in hypertime, things are slowed down, but not stopped,” explained Fink. “Everybody knows that a bee’s wings are nearly invisible and you can’t see them flapping, and the same with a hummingbird’s. People perceive them as incredibly fast, so when they’re not just darting around, when they’re moving very slowly and all they manage to do is get about a half a wing cycle going, it really gets attention.”

High-speed photography of the hummingbirds and insects was impractical given the need to match lighting, camera angles and motion, as well as the degree to which they needed to be slowed down. Hence, the creatures were computer generated. Using Maya as a front end to RenderMan, technicians wrote custom shaders for the bees, seen in a series of six shots that ranged from wide to extreme closeup. “We did some really nice shader work on the bee’s body,” noted Altenau, “and we worked really hard on getting the proper simulation of the multifaceted eyes that bees have. This was also our most challenging use of Jahasa, our in-house fur renderer. Jerry Tessendorf and Dan Weston in our R&D department built up interfaces into Maya and a lot of hooks that we needed to control all the classic things with fur – density, curl, color, luster. An actual follicle model accounts for the shading of the fur at a sub-pixel level.”

For photorealistic hummingbirds, seen in two shots, modelers built translucency and a subtle iridescence into the wings. “We debated various techniques for how to best represent the feathers,” recalled Altenau. “With feathers, you can actually take a bit of a fur approach, with many, many small pieces of geometry. We took a hybrid approach. For areas where we wanted a fluffy, layered look, we added geometry. We also did an extra edge treatment to eliminate that hard CG edge, although the bulk of the bird across the middle of the body is fairly simple geometry.” Though very little of it would actually be seen, animators implemented a full wing cycle for the birds in order to ensure that the motion was realistic, and to give the director a choice as to which part of the cycle he wanted to use in the shots.

As in the kitchen scene, digital water would play a part in the backyard scenario, in the form of frozen spray emanating from a lawn sprinkler. In one striking shot, Cinesite was called upon to illustrate how the frozen spray would react when disrupted by Francesca’s hands intersecting the droplets of water. Two problems had to be resolved in executing the effect — one creative and one technical. From a creative standpoint, the CG artists had to decide how the frozen water should behave on contact with the character. After numerous discussions on what might happen in real life, they opted for a simple storyteller’s approach, applying artistic license to the effect. “We used educational films as reference,” explained effects art director Lubo Hristov, “but a high-speed camera shows things far outside of people’s normal experience. If you look at very high-speed water reference, it looks more like mercury; so you can simulate it perfectly, and it still looks weird — people don’t recognize it as water.”

“We tried to avoid the blobby outer-space look,” added Fink, “since gravity ostensibly still works in hypertime. What we found was that we were doing something no one had done before — rendering CG water droplets moving so slowly that there is no motion blur. Without motion blur, tiny water droplets become incredibly difficult to replicate. Refractions and specular highlights, which are sub-pixel in size, tend to turn on and off as the water or camera moves. This effect disappears when the droplets are rendered to move normally, but it can look obnoxious when they’re rendered to look nearly static. We spent quite a bit of time manipulating contrast and focus in the refracted backgrounds and reflected highlights to control this artifact.” Ultimately, the shots were accomplished with a custom blobby renderer, written by Chris Horvath. “Chris wrote the renderer to optimize the computation required for thousands of refracting droplets in a very short time. It was key to completing all of the sprinkler shots and maintaining a realistic look to the water.”

From a technical standpoint, Cinesite also had to figure out how to get its CG water particles to interact with a live-action figure without precisely recreating that figure in the virtual world. “Francesca walks right into the middle of the sprinkler,” Altenau observed, “so we needed to have CG particles that would go both behind and in front of her. They needed to be articulated around her exactly, especially since she touches the water, as well. For expediency, we just did enough inverse kinematics and match-moving on a rough CG stand-in of the actress for the particle interaction to be acceptable. We didn’t try to match her exact profile. From that point, we rendered the water in layers and let roto or bluescreen mattes take us the rest of the way, sandwiching her between the water layers.”

To depict the frozen backyard swimming pool, Fink opted to use Cinesite’s proprietary Cinespeed software. A cousin to sophisticated feature-based image tracking and stabilizing software, Cinespeed uses pattern recognition techniques to discern differences between adjacent frames, and to insert as many ‘in-betweens’ as are requested by the user, providing the ability to arbitrarily re-time live-action footage as needed. “We were prepared to create fully 3D water for the swimming pool,” said Altenau, “but Cinespeed allowed us to work with the original film, slowing the full 24-frames-per-second water down to the speed we needed. Although we almost completely froze the photography, we avoided the usual problem of discernibly frozen film grain. We shot with the right film stock and lighting, so we minimized grain to start with; and since we didn’t totally freeze the image, the grain always remained slightly in motion. We further diminished it as best as we could in software, and then re-grained the resulting footage.”

Relishing their newfound power, Zak and Francesca decide to go downtown to explore the mischievous possibilities of hypertime. The filmmakers used combinations of overcranked camera work, multipass motion control and plenty of pantomime to capture the teens turning the tables on a graffiti tagger, a would-be bicycle thief, a used car salesman and a meter maid with a predilection for unwarranted parking tickets. Later, the pair stops in at a deejay spin competition where their friend Meeker (Garikayi Mutambirwa) is performing. Under cover of hypertime, they decide to augment his act with a snappy dance routine by invisibly manipulating his body so that he appears to be performing gravity-defying moves. The comic sequence was achieved through a combination of greenscreen compositing and clever editing. “We filmed the dance party scenes at a club called Giant, a few blocks from Cinesite,” related Fink. “We had to have the actor on a wire rig, but we couldn’t shoot him in the main room because it was impossible to suspend a wire in there. So we set the rig up in a different room and shot him against greenscreen there. We shot the background plate in the main room, ran the video-assist tape over to the other room, then used the video to line up foreground and background, which was dicey, because you don’t get a lot of detail out of those video tap images.”

While Zak and Francesca enjoy themselves at the expense of others, watch inventor Earl Dopler (French Stuart) experiences the darker side of his invention at the hands of his employer, industrialist Henry Gates (Michael Biehn). Having learned that government funding for his research has been suspended, Gates forces Dopler to continue his work on the watch, keeping him in a permanent state of hyperspeed, locked in a secret laboratory ‘clean room’ reachable only after passing a high-security retina scan. To produce the digital retina scan effect, production called upon Pacific Title Digital. “We were creating the retina effect from scratch-trying to get something unique for the director,” recalled Pacific Title compositing supervisor Kenneth Dackermann. “We used Maya and RenderMan to create a beam that comes out, scans the eyeball, then recedes into a device. We looked at a lot of other movies to see if something similar to what we had in mind existed. Nothing showed an actual element coming out; only scanning occurring on the eyeball surface itself. Our 3D artist, Bill Leeman, went through an extensive review process, giving the director about eight different looks from which to choose. We finally zeroed in on a 3D vortex effect.”

Though Dopler himself is invisible, his activities in the clean room, viewed from the perspective of the normal world, appear as a blurred flurry of moving magic markers, whiteboards, chairs and soda cans. At one point, Gates floods the chamber with super-cooled liquid nitrogen – a quick-and-dirty method for slowing down hypertime subjects. Previsualization work by Andrew Honacker once again helped Fink plan and execute the sequence. “We had to determine how many passes we’d shoot, and how many layers of smoke we would need for the liquid nitrogen,” explained Honacker. “We also thought we’d have to plan how to rig all the moving objects; but after working with the previz, Mike figured out a simple approach involving multiple passes of the same room with objects relocated in different places. For example, if we had to have a Coke seem to move by itself, we’d put it in one location for the first pass, and then move it to a different location for the second pass. All the compositing department had to do was a quick two-frame motion-blurred transition between the two positions. The production didn’t have to worry about rigging each of the objects with armatures or special effects, as was the original thought.”

Under interrogation by Gates, Dopler admits to having sent a watch prototype to physics professor George Gibbs, hoping for assistance in fine-tuning his invention. Enraged by the breach in security, Gates and his henchmen pay a nighttime visit to the Gibbs home, armed with high-tech super-soaker squirt guns containing liquid nitrogen. A short battle ensues as Zak eludes the intruders and escapes with the watch.
For the liquid nitrogen gas blasts, Fink had considered a CG particle system, recognizing that it could provide a convincing look, though historically, gaseous forms have been difficult to simulate digitally. Ultimately, Cinesite executed the effect using volumetric rendering in combination with a particle approach. To provide the illusion of interaction between CG gas and a live person, Fink employed the same set of techniques that had allowed Francesca to interact with a CG sprinkler — gross particle collision against roughly matched 3D forms, fine-tuned through 2D roto mattes.

One of the most challenging aspects of the gas effect – liberally featured in the film’s many action scenes — was figuring out how to make a character blasted by the liquid nitrogen appear frosted. Dissatisfied with initial color-correction experiments in which characters were given a blue caste, Fink sought an alternate solution — a frost element that could warp with a live-action human figure without digital artists having to animate a matching 3D model. “Every time someone was shot with liquid nitrogen,” recalled Lubo Hristov, “we created a single-frame artwork frost element using reference photography of all these crazy people who go up Mount Everest. We worked in a single frame so that we would have more control over the matte painting and so the texture wouldn’t ‘boil’ over time, as multiple uniquely painted frames would. We then used in-house software to ‘stick’ the single frame onto a moving person — kind of like feature-based motion tracking.” Though the result was encouraging, Fink wanted more, and finally pinpointed what was missing from the frosted look. “It just didn’t look cold enough,” Fink recalled. “Most people recognize ‘cold’ as ‘vapor that falls.’ Anything that’s really low in temperature — a piece of dry ice, or something you take out of your freezer on a damp day — exhibits the effect of mist falling from it. Once we added that, it really worked.”

In a subsequent nighttime chase sequence, Gates’ henchmen pursue a van driven by Zak through frozen city traffic. Fink hit an immediate problem during live-action filming of the scene. “The sequence was shot with pantomiming actors,” Fink explained, “and, with the exception of the hero vehicles, slow-moving cars. The camera was required to move quickly with the moving hypertime van and car, leaving everything else behind. Because of this fact, the background elements could have been moving or not, and you wouldn’t really notice the difference. Since it wasn’t immediately obvious, we needed a way to make it clear to audiences that this was a hypertime chase sequence.”

Fink and Hristov took their initial inspiration for the shot from scientific principle. “We drew from the Doppler Effect,” Fink elaborated. “When a train is approaching, its sound waves are compressed; when it recedes, its sound waves are stretched out. So it has a higher pitch coming toward us than it does going away. Light waves do the same thing, but they change color instead of pitch. Light is bluer on the approach, and redder going away. Since this was a night sequence, we did some tests with Cinespeed and latency and other techniques to streak headlights and taillights on frozen objects. We finally abandoned science for creativity, and decided to give everything a lavender/green shift. Originally, the plan was to streak only moving lights — but we extended that to include all lights seen from a hypertime frame of reference.”

Fink worked with Jason Piccioni and the 2D crew to accomplish the necessary streaking, choosing between two techniques on a shot-by-shot basis. “If the camera was locked off and the cars were moving through frame,” said Fink, “we would isolate the lights with a luminance matte with maybe a garbage matte here and there to exclude street lamps. When the camera was moving as well, but we didn’t want its relative motion to contribute to the shape of the streak, we would take one frame of a headlight and give it a target position further on down the line and streak between source and target positions while ignoring the camera motion.”

When Gates abducts Zak’s father, threatening harm to his family if he refuses to perfect the watch technology, Zak — aided by Francesca and Dopler — plans a bold rescue. Arming with paintball guns jerry-rigged with coolant tanks and liquid nitrogen pellets, and under cover of hypertime, the trio infiltrates the lab where Zak appropriates a bicycle and races through the corridors, dodging frozen lab technicians and armed hypertime guards. Live-action plate photography for the scene was handed to Pacific Title Digital for postproduction enhancement. “Production gave us a series of shots in which actors pretended to be frozen,” related Kenneth Dackermann, “and we needed to smooth out the performers’ imperfections. In one shot, Zak was racing his bike through the clean room, and one of the supposedly frozen characters flinched when he came close to her. In another shot, Zak’s stunt double, intending to leap his bicycle from one countertop to another, landed a bit short, striking instead a precautionary safety board that had been stretched between the two surfaces. When we digitally retouched the board from frame, the rear bicycle wheel looked mysteriously unsupported on impact. We corrected all these things by painting missing elements or borrowing elements from adjacent frames and tracking them into the overall motion of the shot.”

Toward the end of the film, Zak and Francesca are captured and forced into hypertime along with Zak’s father. While they are held captive in the clean room, Gates causes the entire building to go into hypertime – depicted by the Cinesite crew as a warble effect. “The room warble is an energy field that envelopes the chamber,” explained Dave Altenau. “It grows in a concentric, circular way and spreads, following the surfaces of the room. To accomplish this effect, we rendered in layers and did very rough modeling that was just enough to give us perspective and foreshortening of our animated texture maps. The room contained all kinds of very complex grid work, and we wanted our energy effect to look like it was following that grid work specifically; so we modeled approximate 3D shapes over which we animated our textures, and we did the fine work with roto mattes in the comp to articulate the details.”

In a bid to escape, Zak propels himself into a dangerously over-accelerated state called hyper-hypertime in which his molecules are moving so fast that he becomes less corporeal and, thus, able to pass through solid objects. Featured in some forty shots, the extreme hypertime would present Cinesite with an interesting creative challenge tantamount to nesting levels of hypertime, one inside the other, like Russian dolls, without confusing the audience. “The whole movie is about hypertime,” observed Lubo Hristov, “but suddenly we had to go to hyper-hypertime. This raised questions in terms of the hyper-hypertime point of view — if everyone was already frozen in normal time, were we going to have hypertime people also appear frozen from the point of view of someone in hyper-hypertime? How were we going to differentiate the two levels?”

After deliberation, Frakes and Fink settled on yet another rule of hypertime — the camera never enters hyper-hypertime; it captures only the hypertime perspective. In this way, real-time people would appear frozen, hypertime people would appear normal, and hyper-hypertime people would appear somehow transformed. Frakes wanted hyper-hypertime Zak to look as if he were emitting light, like an energy being almost on the verge of disintegration. To accomplish the effect, Jesse Bradford was shot against greenscreen, treated with a number of image processing techniques to achieve the desired glow and transparency effects, then inserted back over the backgrounds. Digital artists used Discreet Logic’s Flame software to create a difference matte between successive frames in order to layer a motion-inspired halo effect over a base glow — the more Zak’s body parts moved, the more light he would emit. Although largely automatic, the procedure required much artistic supervision. Glows had to be sustained and created from whole cloth when Bradford stopped moving, and glows on the actor’s face in closeups had to be heavily manipulated so that they did not distract from his performance.

The sequence concludes with a shot in which Zak, protected by hyper-hypertime, leaps from the clean room catwalk as Gates blasts him with liquid nitrogen, effectively freezing the teenager in mid-jump and causing him to drop as he reverts back to normal hypertime. For that pivotal moment, Frakes had envisioned Zak freezing in midair, then crashing to the floor while the camera continued to dolly. Recognizing the shot as a signature camera array effect, Fink enlisted the aid of Reel EFX to shoot the leap with its Multicam system. “What happens in a still array shot,” Fink explained, “is that you’re replicating a camera dolly — but rather than moving the camera, you’re setting up a still camera at every position the motion picture camera would normally be getting an exposure.”

The setup required for the still array would involve extensive previsualization to ensure that the potentially complex shoot would be a productive one. “We only used the still array once in this entire film because of the shooting schedule and production budget,” Fink acknowledged. “The producers carefully chose where they wanted to spend their money. We used it here because the effect had to occur without a cut while Zak was in the middle of falling, and the camera move called for was too fast to be achieved any other way.”

The previsualization was shared with Reel EFX to assist in preparing for the shot. “We had to know exactly where all the cameras were going to be pointed system,” noted Reel EFX senior project manager Tom Costan, “so Andrew Honacker created a virtual version of our Multicam equipment in his computer. At my request, he made a line drawing of the rail that the cameras would be mounted on, and a laser-line representation of where each camera would be pointed in space. That gave us a 3D spline of the path of the cameras. So at each camera location, we had a laser line going out, projected along the camera lens, intersecting a virtual plane, that told us, in theory, where we needed to aim our real-world cameras. We built a real 2D targeting grid based on that information, and it worked out very well.”

Choreography and shot logistics were worked out with a stunt double for Jesse Bradford on a flying rig engineered by Stan Parks and R.J. Hohman. Then, with the real actor in place, seventy-five Canon single-lens reflex cameras distributed along a curved forty-foot rail captured the action. Each camera was controlled by its own microchip in order to ensure precise timing. Failure of the cameras to trigger simultaneously would cause jitter in the resulting image, destroying the illusion of the frozen-moment dolly shot. The biggest challenge was determining whether or not the setup had succeeded in capturing the flailing, imprecisely-timed fall in frame. “We have a video playback system that shows you the images from four cameras,” said Reel EFX owner Jim Gill. “In this instance, we had video input from the beginning of the array, two places in the middle, and at the end. When we played the video back, frame by frame, we could see exactly where the performer was.”

To be sure he had what he needed on film, Fink employed one other technique. Since the eight-perf format of the still cameras effectively supplied Fink with extra-large Vistavision images of the fall, he opted to frame his subject in wide angle, scan the film at double the normal 2000-pixel-wide resolution, and achieve precise framing in post. “After scanning and stabilizing the frames from the camera array,” recalled Fink, “we wanted more flexibility in manipulating Zak’s animation as he dives across the room. To accomplish this, we decided to create a 3D version of Zak and use selected frames from the camera array to project textures onto the model. This allowed us to quickly create a photoreal 3D version of Zak and animate him through the scene as a 3D model. Not only did this give us complete control over the animation and timing of the shot, but it allowed for perfect integration of more than eight 3D elements, including six CG vapor passes, a frost layer when Zak gets hit by the liquid nitrogen gun, and the CG version of Zak.

Clockstoppers concludes with an explosion of liquid hydrogen in the lab clean room that decimates the facility, freeing the hostages and bringing about the arrest of Gates and his cohorts. The explosion was filmed on a quarter-scale miniature of the clean room built by Grant McCune Design to match the full-scale set. Pyrotechnics for the scene were provided by Ritchie Helmer and shot by Bill Taylor. “We built the surrounding lab,” noted Fink, “as well the teepee-structure clean room inside it, and all of the surrounding catwalks and tanks and pipes and miniature lights. We did speed tests with a motion picture camera in the parking lot of Grant’s place to see when we needed to set off the various charges to make the glass break. We shot it in two takes — as planned — because the physics of the explosion inside this little teepee shape were bizarre. To get multiple takes, we built the basic structure of the miniature out of steel. The model didn’t really need to blow up — we just needed to blow out the glass and furniture. So we had doubles made of all the breakable things, shot our first take in the afternoon; and by night, it was cleaned up and back together again, ready for take two.” People reacting to the explosion were subsequently composited into the shot by Cinesite.

Clever in execution and original in approach, Clockstoppers challenged its resourceful effects crew to convey its story in a visually arresting manner that presented new riffs on the age-old theme of time manipulation. “Cinesite did not have a lot of time on this project,” acknowledged Gale Anne Hurd, “and I’m really impressed with how quickly they were able to solve the various problems that they faced in terms of hypertime. When I think back on other visual effects films, I realize that people often have a year or more to visualize, create and deliver the final shots. On this film, it was closer to four months. But I completely believe that if you have the right people working with you – which of course was the case with Cinesite and Mike Fink – that they will rise to the occasion.”

Clockstoppers photographs copyright 2002 by Paramount Pictures Corporation. All rights reserved. Production still photography by Claudette Barius. Effects unit photography by Eric Swenson. Additional photographs courtesy of Cinesite. Special thanks to Rita Cahill, Nikki Hochstein and Kristine Gierthy.

Written by Joseph Francis. Text copyright 2002 Cinefex.