Visual effects supervisor Greg McMurry oversaw 800 shots for I Am Number Four, the story of an alien fugitive on the run from other-worldly pursuers. We take a look at some of the key effects scenes from the film.

I Am Number Four follows John Smith (Alex Pettyfer), one of nine aliens with special abilities from the planet Lorien hiding on Earth from the evil Mogadorians. The 'Mogs' are on a mission to murder each of the nine, of which John is Number Four, with the help of their alien attack-like dogs called Pikens. Avoiding the Mogs by hiding out in a mid-Western town, John slowly discovers he has special powers, known as Legacies, that can help him against his attackers, even though the powers make him feel an outcast at school and in front of his new love, Sarah (Dianna Agron).

To help director D.J. Caruso realize the creatures and effects necessary to bring the film to life, VFX supe Greg McMurry called upon several visual effects houses. Industrial Light & Magic created the Piken creatures and another dog-like animal that is John's protector. Entity FX devised shots of the Mogs disintegrating as they are killed, as well as teleportation and sword work. Hammerhead was responsible for John's powers of Lumen and telekinesis, as well as Mog breathers and ink effects. Shade VFX delivered laser blasts, set extensions, a CG gecko and a torture ball. Rounding out the visual effects work was The Pixel Playground, Kaliber Visual Effects, Lola Visual Effects, The Creative Chamber, DIVE and Base FX, plus a number of freelance artists, with The Third Floor contributing previs for the entire show. KNB EFX Group handled make-up effects.

Legacies, breathers and ink

John's powers as Number Four are slowly realized throughout the film, manifesting in an ability called Lumen and a form of telekinesis. These powers were created by Hammerhead under visual effects supervisor Justin Jones. "The Lumen comes out of John's hands in terms of light," says Jones, "but it's an energy that boils up under his palms and shoots out, and he ends up being able to use it as a flashlight or as a weapon against the Mogs."

John discovers his Lumen legacy in 'I Am Number Four'

The Lumen was initially devised as a powerful beam of light shooting out to the edge of the frame, an effect ultimately toned down to match some of the on-set interactive lighting and lighting rigs worn by the actor." We just tuned our Lumen to fit that," says Jones, "but we had a small range that we went outside of. In the end it was a more photoreal and less magical effect coming out of his hand."

The final Lumen look became a mix of volumetric emanating from John's hand, with Maya used to render 3D content and noisy shapes within the rays. Hammerhead built some 3D tools in Nuke to match that look so that many shots could be achieved in the comp. "It was all about the energy coming from his hand," says Jones, "and one of the biggest struggles we had was not blowing out the core of his actual hand. D.J. always wanted to feel the energy, and there was always a spectrum of color at the core, so it wasn't just white."

"We also added some veins and bones on top," continues Jones, "so that it was glowing underneath the skin, for when it wasn't turned on all of the way. Then we always added some turbulent moving waves of color at the palm. For the back of the palm, we did an effect like the one you see when you put a flashlight against your hand and you can see an orange glow."

The telekinesis effect, in which John is able to move objects or people at will, relied on no particular glow or interactive light, but instead just a suggestion of movement. "D.J. didn't want any confusion between Lumen and telekinesis," notes Jones. "So the effect became a matter of warping the background from John's palm. That was mostly 2D, but did have some 3D elements - it just depended on the shot. If it was against a black sky, no matter how much you warped it you didn't really see it, so sometimes we needed some material. We did a bunch of noise patterns of these spheres shooting out. We also sometimes did some 3D elements of light kicking off the telekinesis, but never like it was an inner glow. The telekinesis was definitely more of a feeling."

Hammerhead's work extended also to enhancements of the breather slits seen on the cheeks of the Mogs. Using the existing breather make-up, artists chose specific shots to show the slits breathing and with some glowing red texture and atmosphere beneath. "For this," says Jones, "we did all the spline warping in Shake and the compositing in Nuke. A lot of it involved tracking at first and then blending the make-up. On top of that we would widen and shrink the four scales on each side of the nose, and then add the red texture we had built."

Earlier shots of John seeing a vision of Number Three being killed while he is in the ocean were also Hammerhead creations. Here, inky depictions of the murder and the Mogs are revealed to John under the water. "We used Krakatoa for the ink look," says Jones, "mixed together as many layers and mapping those to the 2D footage that was shot and adding bits of plankton and particulate. The Krakatoa artist would take the footage and apply the ink to that and it would peel off, but keep that color as it was swimming around."

How to kill a Mog

John and other characters in the film dispatch the Mogs in the final battle sequence, and throughout the film, using various methods - swords, Lumen and laser rifles. When killed, the Mogs immediately turn into a rock-hard gray plaster and then into dust that floats away (partly to explain why no alien traces are left on the planet). The disintegration effect was achieved in stages by Entity FX under the supervision of Mat Beck, ASC.

For the first stage, in which the Mog turns gray, artists isolated the character and performed a desaturation. "Often it was a dark scene, and the character was wearing black," notes Beck, "and simple desaturation didn't really show up. So we would track and deform a more interesting gray texture to stick on the character."

The second disintegration stage involved the Mog taking on the rough surface of the material that it would be breaking up as, almost a dusty rocky plaster. "We built a 3D version of each character that died, and tracked its motion to the real character in 3D space," says Beck. "The living character transformed into the statue along a boundary made of fractal fibers that grew and filled in as it advanced along the body. Sometimes we would add a bit of a time warp to help freeze him into place."

"D.J. wanted it to be clear that a 3D object was disintegrating," continues Beck, "so we broke our statues into large chunks, which in turn gave birth to smaller pieces, which in turn broke into smaller particles. We had a lot of force fields and turbulence on them to give them good energy and complexity before they dissipated. At the end we got the request to add one extra moment to two close-ups, so instead of just stopping at a stone texture, the Mog transformed to a skull face. We even added a little energy zap at the end of one shot to give Greg McMurry a punctuation point that he wanted. It worked great." Artists mostly worked in Maya using both particle and fluid sims to achieve the effect, then in 2D and two-and-a-half D for the finals through After Effects, Nuke and Flame.

Mirroring the Mogs in 3D gave other benefits. One shot featured a Mog's arm and hand and sword in the foreground. "The hand was out of focus and so dark that you couldn't see the transformation," says Beck. "With the fully CG arm, we could make it brighter and sharper and pull focus to the foreground as the hand and sword turned to stone."

For a combat scene in the truck cab, Entity tracked in a CG windshield, sword, glass particles, blood, and two CG hands - one holding the sword and one getting stabbed. Entity was also responsible for scenes of Number Six teleporting, achieved as a light and energy effect. "We did quite a few shots where the character disappears in one part of the frame and reappears in another part," explains Beck. "The idea was to give it a certain amount of color and impact and energy. We modeled her in 3D so we could generate elements tracked to her movement, which allowed us to distort the background in an interesting way to time with her disappearance. Greg wanted her colors to carry into the energy field, so we mixed an electric blue with a saturated yellow from her hair. Because these scenes often played dark, these flashes of brightness really popped off the frame. The more colorful painterly streaks we added, the more D.J. liked it."

A colorful shoot 'em up

"the lasers blasts were warping the background behind them, so they needed to have 3D renders"

Bryan Godwin
Shade VFX supervisor

Shade VFX designed and implemented many of I Am Number Four's energy weapons, in particular those used by the Mogs and another alien, Number Six (Teresa Palmer). After an R&D period, Shade settled on a 3D approach for the laser blasts. "Everything was rendered out of Maya in terms of 3D lasers going through," says Shade visual effects supervisor Bryan Godwin. "They had a unique texture and shape and were warping the background behind them, so they needed to have 3D renders moving through space rather than just 2D muzzle flashes."

Watch the hallway fight from I Am Number Four

Number Six sports a pulse rifle that tied into the look and feel of her other powers, including teleportation and her forcefield effect. The Mog commander is able to use an almost bazooka-like weapon to destroy parts of the school sports stadium with laser blasts. "For those," says Godwin, "we essentially built a hair system of sorts that we attached to a ball. This hair system created this interactive and dynamic tail that would come off the back of the energy pulse. I thought that was a unique way to approach it because usually we weren't using geometry or particles to get the look." The blasts were rendered in VRay and composited in Nuke, and were also added into set extensions of the stadium along with CG fire and smoke and various damage and destruction pieces."

Shade also contributed a fully CG gecko, which later becomes the dog Bernie, into early scenes as it tails John. "We tried to instil some character into the gecko without it being cartoony," says Godwin. "We used Maya for him. Our skim deformations were actually cloth simulations - little lizards have very leathery, crinkly skin that's very thin, not like a wet skin. It wrinkles up and crunches. We tried some muscle systems but what worked best was turning the entire skin of the animal into a cloth sim."

Further CG work included shots of a Mog torture ball fed to a hapless civilian who initially tries to help the aliens capture John. "The Mog commander pulls out this rusty steel ball," says Godwin. "Out pops these circular steel blades and he feeds it to the guy. It was a particularly grim and gruesome idea, but it's played quite funny by the actor. In camera they shot him holding a ball and we replaced that with a fully CG prop of the weapon."

Creating killer machines - the Pikens

Although they make a brief early appearance - to help kill Number Three - the Pikens are spectacularly revealed in the fim's climax as the Mogs zero in on Number Four. "The Pikens went through a wide conceptual process," notes McMurry. "We wanted to create animals that were vicious, but didn't necessarily look like anything in particular from Earth."

ILM's art department used the principal photography period, which took place in Pittsburgh, to revise the designs of the two Pikens seen in the film. "ILM's visual effects supervisor Bill George led the ILM effort to create these two distinct creatures," says McMurry. "We wanted the audience to tell that there were two different ones, so that they didn't think there might be an endless number of Pikens coming out. Then we went through this whole process of what makes the Piken a killing machine - he's out to kill and has no other purpose than to attack."

That process resulted in nine foot tall creatures acting almost as hunting dogs and appearing somewhere between a giant flying squirrel and a reptile with large spiked claws. "We made them fly, but more so they were jumping rather than flying like a bird," says McMurry. "They were so powerful they could leap hundreds of feet at a time. We worked out a webbing in their legs to give them that ability."

“Peter built this giant 18 by six foot steel hammer contraption that was hydraulically powered from the back,”

Greg McMurry
Visual effects supervisor

The film's end battle, in which Number Four, Sarah and the newly arrived Number Six confront the Mogs and Pikens, takes place inside a high school and adjoining sports stadium. For the first appearance of a deadly Piken as it crashes into the school cafeteria, McMurry collaborated with special effects co-ordinator Peter Chesney and director of photography Guillermo Navarro to achieve the resulting mayhem practically and with as much interaction as much as possible before ILM added their digital creature. "Peter built this giant 18 by six foot steel hammer contraption that was hydraulically powered from the back," says McMurry. "There were real glass windows in this place and this thing would crash through and recoil itself fast enough so it wouldn't be in the picture any longer than we had to have it. Then ILM went in and animated the Piken coming through that window."

On set, McMurry chose to acquire the plates using multiple pass motion control photography, since pieces of wood, furniture and glass were likely to cause a hazard to the actors. The creature's proposed movements were blocked out in previs by The Third Floor, then divided up into the multiple passes required. "Peter Chesney and I worked out the timing for the triggering of each of these crash events," recalls McMurry, "and then we did some tests to figure out the exact frame in advance to trigger the hammer so it would come right through for the planned camera move."

Tables, chairs and other flying pieces were rigged with separate pulling mechanisms that were also triggered on the precise required frame. "Then we had to do a pass that tied all our actors in there because it was so crazy with all these gags going off," says McMurry. "These were at least five pass shots. There was no way you could have actors standing around while glass was breaking and steel was flying."

In addition to the Pikens, ILM developed a creature that comes to the aid of John during the battle sequence. Initially seen as a gecko and then a dog called Bernie, the creature is revealed as John's protector, transforming into a large and vicious animal that is able to wrestle and subdue a Piken.

On a tight schedule - around only four months - Greg McMurry and the visual effects vendors delivered significant work that placed a number of otherworldly beings in some very real environments and predicaments. "One thing I really enjoyed was putting our young characters in big battles with the aliens who have big blasters that we basically all invented," says McMurry. "Our rationale was that the aliens wouldn't be coming down to shoot bullets at each other, so we wanted to make them more colorful and exciting.  I am proud of all of our efforts to create great tension and excitement throughout the movie."


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