Cinefex Weekly Update | Issue 33

To create the nexus of the effect, ILM lead CG modeler Michael Koperwas designed a series of glasslike digital shapes -- spheres, ovoids, rods and interlocking orange-segments -- which lead animator Paul Kavanagh articulated to describe motion like shifting tumblers in a combination lock. "It was an abstract art style of animation," said ILM animation supervisor David Andrews. "We made the pieces pop and flip and spin, and applied them to this completely bizzare creature. Alfonso wanted it to behave like a visual representation of a radio tuner sound, picking up these different nightmares. We tried to give it a very frenetic quality to match that weird sound, and used the animation principle of a bouncing ball -- it anticipated the action by a couple of frames and then popped and changed shape, like a frog squishing down and then hopping."

The spinning, shifting pieces drove transformations between Boggart forms, culled from a library of live-action images representing elements on the Boggart nightmare scale. "Alfonso asked us to come up with 100 different scary things that we thought would make interesting images," related Guyett. "He was very good at tapping into the kinds of things kids are afraid of -- things within their own set of experiences, like the classic fear of going to the dentist. But we also tried to put an angle on it because these were Hogwarts kids, not in the normal world." The production allocated a Boggart shooting unit to film a wild variety of childhood fears -- including a dentist, a crocodile, a shark's mouth, lunging knives and a flamethrower. Censorship concerns of placing children in peril whittled imagery to a handful of horror archetypes -- a gecko, raven, witch and snake - which ILM mapped and revealed subliminally in the shifting CG object.

The first Boggart apparition involved the appearance of Hogwarts Professor Severus Snape (Alan Rickman), who terrifies Neville Longbottom (Matthew Lewis) before acquiring women's apparel. "We used a small motion control rig where we hand-operated and recorded the move," related Guyett. "We filmed Alan Rickman stepping out of the wardrobe in his professor robes and recorded the move. We then dressed Alan as a woman and played back the selected take. Alan is such an incredibly skilled actor, he matched his movements exactly; then, ILM did a fantastic job of matching Snape in his robes to Snape in the dress, through what looked like a handheld camera move."

ILM next modeled and animated a giant spider, reminiscent of the monstrous Aragog from Harry Potter and the Chamber of Secrets, to terrify Ron Weasley (Rupert Grint) before the young wizard succeeds in conjuring rollerskates onto the spider's feet, causing the giant arachnid to skitter and skate. The third candidate (Sitara Shah) transforms a giant lunging snake -- another ILM animated character -- into a giant jack-in-the-box, constructed as a full-scale animatronic by creature effects designer Nick Dudman.

The sequence then concludes with Harry Potter facing his own demon -- a towering spectral form representing one of the robed prison guards from Azkaban wizard prison. One of the most nightmarish creatures in the film, the form was generated digitally by ILM. "The Boggart started out as a longer sequence than it appears in the movie," stated Guyett. "But it was a cute idea, and short and sharp is probably the way it should be."

For more on the effects from Harry Potter and the Prisoner of Azkaban, look for Cinefex 99, coming in September.