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MillimeterStep by Step: The Spiderwick Chronicles
Feb 22, 2008 4:12 PM, By Ellen Wolff
A signature moment in the Paramount/
Nickelodeon release The Spiderwick Chronicles arrives when we meet an elfin creature amid the musty shelves of a spooky old house. It’s a tiny man with rat-like ears called “Thimbletack” (voiced by Martin Short), and he possesses the power to transform into a mischievous boggert when he becomes upset. Being discovered sends him into a panic, and this provides a showcase for the CG creature animators at the San Francisco studio Industrial Light & Magic (ILM).
ILM Visual Effects Supervisor Tim Alexander has encountered with digital elves before, having worked on Harry Potter films that feature the talking house elf Dobbie. “But the complexity of Thimbletack is quite a bit higher,” Alexander says. “We learned a lot from the Davy Jones character in Pirates of the Caribbean[: Dead Man’s Chest and At World’s End], and we tried to apply what we’d done with Davy’s eyes to Thimbletack.”
ILM’s artists began by studying The Spiderwick Chronicles books that inspired the film, and they created numerous pieces of artwork and a computer model of the character. A physical maquette was also made, which allowed director Mark Waters to study Thimbletack from different angles. Once approved, that maquette was scanned into the computer.
“In terms of modeling, he’s a pretty dense character, with a lot of detail,” Alexander says. “There are lots of displacement maps to create wrinkles in his skin. All of those details had to be dialed in on a per-shot basis, because as we got further away from camera we found that we had to amp that up so you could still see them. We had to balance between making this guy look old—versus too old.”
To develop Thimbletack’s body language, ILM Animation Supervisor Tim Harrington was videotaped, which yielded a kind of rough movement previz. “Tim also did a lot of motion capture on this film—not to apply directly to Thimbletack, but for quick motion tests,” Alexander says. Since the character was so small, human movements had to be scaled downward, or retargeted. Ultimately, Thimbletack’s movements were keyframed animation.
A major challenge was animating his face, including the way he delivered the lines read by Martin Short. Reference video was made of the actor, and a huge assist came from the studio’s new proprietary facial animation system, called “Fez.” It’s integrated within ILM’s software environment Zeno, but it also functions with Autodesk Maya, which is used for modeling and animation. “Animators can work in both packages equivalently,” Alexander says. “Fez lets us keyframe, as we did with this movie, but also lets us take motion-capture data and modify it.
“Fez classifies the muscles in the human face, lets us solve a face for its muscle systems and then apply that same movement to an alien creature’s muscle systems. We’re able to retarget the data and have it look different on each creature because their facial muscles might be in different locations. You have to know how both faces move, but if a muscle fires in one face, it will fire in the other face. It might give you a different shape, but you still get the same timings, which is what’s important to a performance.” Alexander cautions that there’s a danger, with human-like facial animation, of getting into that creepy-looking territory that animators call “the uncanny valley.” “It’s a tricky business,” Alexander says. “The Fez system helped us in this case because we able to keep the character of Thimbletack on model better. His face didn’t get as screwed up when the animators were dialing things in, and we could easily save different facial configurations.”
Because Thimbletack appears frequently in The Spiderwick Chronicles, ILM built a library of facial movements that the animators could draw upon. “We could save oohs and aahs so that animators could block things in quickly,” Alexander says. “Even in the blocking stage, an animator could do a pretty full fledged vocal performance. Once they got the timing down, they could massage it so that every time the character says ‘ooh,’ it doesn’t look exactly the same. In the past, we wouldn’t even touch the face until gross movements were blocked in. Now, we can get into facial motions much earlier to express the performance for the director.”
A key part of creating Thimbletack involved simulating convincing-looking skin. “By the time simulation happens, we’re in Zeno,” Alexander says. “Lighting is done in Zeno and rendering is done in [Pixar’s] Renderman through our Zeno interface. For Thimbletack, we made extensive use of the subsurface scattering techniques that we’ve developed in the years since we animated Dobbie. We use that quite a bit for back lighting behind characters with large ears, like Dobbie and Thimbletack. We have light showing through their ears, and we now have more control over the areas that the light influences.”
To insure that Thimbletack looked consistent, ILM spent considerable time building what Alexander likens to a spread sheet in Zeno, which could be referenced by everyone. “It sort of says ‘Thimbletack: left cheek wrinkles’—with a dial from zero to one. That took quite a bit of time to set up, but later we got a lot of people doing shots that looked pretty consistent.”
Cloth simulation for Thimbletack’s multilayered costume represented a new area of development. “One of the big things is layered simulation. Thimbletack wears pants and a vest with a shirt underneath it,” Alexander says. “All of those have to interact with each other. We’ve never really had that ability before. We’re actually conjoining our simulation systems.” When Thimbletack inflates his body to become a frog-like boggert, Alexander says that the clothing simulation became very complex. “We went from a closed shirt to his shirt bursting open. We had a couple of sims that took weeks on end.”
Because Thimbletack is a small character, creating properly scaled clothing was crucial. “His clothes are small objects, so you would expect those objects to be stiffer at that scale,” Alexander says. “We played with different stiffnesses to make his clothes feel small. But that made our sims look bad, so we opted for the life-like feel of human clothes with more wrinkles. Technically, our cloth system likes to work at real world levels, so sometimes we’d blow Thimbletack up to be a 6ft. person. We’d do the cloth simulation and then shrink him back down to get him to feel more life-like.”
The final task was integrating Thimbletack into the plate photography. In this scene, the character reacts to being discovered by running away and knocking over bottles. ILM Supervisor Pablo Helman had rigged those bottles on set with wires that could be pulled to upend them, and ILM’s roto artists would later clean up the plate. “When Thimbletack ran away, if the timing of the bottles falling over wasn’t right, we’d respeed the photography to get the timing correct,” Alexander says.
“When we couldn’t do a compositing trick we’d create a CG object for the character to interact with. In this sequence, we had to animate an object that wasn’t moving in the plate photography. I still believe in shooting as much as you can on set because that’s the best way to get realism, but it’s great to have the freedom to animate an object for interaction.”
Compositing all of these elements into the plate was done in Apple Shake. “Thimbletack looks small because of the objects around him. But we also applied a lot of depth of field,” Alexander says. “When you’re shooting something small, it quickly goes out of focus. There were parts of Thimbletack that were out of focus to give you that really small feeling, as if we were shooting macroscopically. We did that as a post process in Shake. We even applied some vignetting effects to make it feel more filmic.”
“[The final feeling] is a naturalistic, organic fantasy, which we haven’t seen much of lately,” Alexander says. “This show is all about subtle character performances.” Capturing those subtleties can add to the level of a character’s complexity, Alexander admits. “We always tend to increase complexity as our processors get faster and our people get better at what they do. It never gets easier.”
Credit Roll
Director: Mark Waters
DP: Caleb Deschanel
For ILM:
Visual Effects Supervisors: Pablo Helman, Tim Alexander
Animation Supervisor: Tim Harrington
Animator: Jakub Pistecky
Creature: Jason Smith
Technical Director: Damian Steel
ViewPaint Artist: Jean Bolte
Compositor: Nelson Sepulveda
Layout: Marla Newell
Modelers: Ken Bryan, Frank Gravatt
Roto Artists: Pat Jarvis, Katie Baird
