The dragon in the Chinatown sequence was needed to relate closely to the parade dragon yet still be extremely threatening. Numerous designs and styles of animation were explored. "At times, it looked more like a dinosaur, a snake, a komodo dragon and a crocodile," Brennan continues. "The final design was a very complex eight-legged creature animated to walk down the street, climb buildings, spray fire and smash through walls using a combination of practical and CG elements."

Asylum's most difficult challenge, arguably, was to transform the parade dragon into the real one. "The parade dragon was modeled and carefully matchmoved," Brennan notes. "Cloth simulations were then used to build a CG version, which could slowly transform into the real dragon. Each shot had to be treated as a separate one-off effect with its own rigs and blend shapes. Asylum's pipeline allows data to be moved very easily between Maya and Houdini, which proved invaluable."

The car chase was another challenging sequence. Once again it is filled with very complex one-off effects: morphing/melting cars, numerous other CG cars, a smoke filled tunnel, morphing people, magical mirrors, exploding glass windows and several fully CG blocks of 50^th street and 7^th Ave. "While filming, the production had absolutely the worst luck possible -- car accidents and the subsequent speed restrictions as well as weeks of torrential rain made it almost impossible to shoot all the elements required," Brennan concedes.

For the transitions, reference plates were shot of each car, but the actual transition was built over the clean plate using fully CG cars. Both cars were scanned and modeled in very high detail and a third model was constructed that performed the blend animation between the two vehicles. This model was used to drive the shapes of the high-resolution geometry in Houdini and create the waves of transforming metal. Several layers of CG water spray were then added to tie the whole effect together.

Once inside mirror world, Balthazar (Nicolas Cage) has to escape back through another mirror to return to the real world, but Horvath is ahead of him, shattering his chances of escape. Asylum used extensive Lidar data to build several full blocks of 7^th Ave. approaching Times Square. Since the windows couldn't really be shattered, the plan was to replace the store fronts of the building in CG.

"This way we could control reflections on the windows to best convey the story of mirror world," Brennan continues. "Ultimately 10 of the shots were fully CG: everything (cars, buildings, road surfaces, sidewalks, street signs, etc.) had to be created from scratch. To pull this off, we combined fully textured, lit and rendered geometry with texture projections built from the extensive photographic reference gathered on set. All reflections had to be removed from the photographic textures and the correct ones properly calculated and added back in the shader. The distant environment was built using Nuke (by projecting additional photographic reference and animated signs) then passed back to the lighting team to be properly reflected into the streets and foreground buildings. The effects team created dozens of elements per shot including fog, drizzle, atmosphere, shattering glass, tire spray, man-hole steam and plasma balls.

"At the end of the day, those 500 effects shots felt like 1,500!

Bill Desowitz is senior editor of AWN & VFXWorld.