Natural effects, unnatural people: Sony Pictures Imageworks creates a post-apocalyptic Manhattan and fills it with plants, animals, and vampires.(CG Modeling)

In the film I Am Legend, when Neville (Will Smith) moves through Times Square, he doesn't see streets filled with people, neon signs, or yellow taxis. He sees a lion stalking a herd of deer. Three years after a rampant virus has caused the evacuation of Manhattan and its ensuing isolation, the island has returned to nature.

Of course, when director Francis Lawrence shot the Warner Bros. film on location, the city was as raucous as always. Sony Pictures Imageworks emptied the streets and did the dirty work that made the city look abandoned.

"We shot all over Manhattan," says Jim Berney, visual effects supervisor at Imageworks. "So, we had to paint out all signs of life. The streets are cracked. Buildings are crumbling. There are weeds everywhere. The wildlife is back in town."

For the buildings, Imageworks artists working in Adobe's Photoshop turned out the lights, tattered awnings, aged and weathered surfaces, added procedural bird poop to photographs taken on location, and more, and projected those textures onto low-res representations of the buildings in 3D geometry.

Modelers built the structures using survey data and LIDAR scans, the latter for a virtual background surrounding Times Square for scenes shot on a bluescreen stage. "We surveyed every location," says Dave Smith, digital effects supervisor. "When we needed higher-resolution, we used the LIDAR scans."

In addition to re-creating plates, the Imageworks crew also built all-digital environments for a seaport sequence during which they destroyed a 3D version of the Brooklyn Bridge. Imageworks uses Autodesk's Maya for modeling and a combination of Side Effects' Houdini and proprietary tools for dynamic simulations. Houdini dynamics set the stage for destruction by simulating the collapse of the large structure; proprietary tools provided fine details. "We drove the crinkling, bending, and snapping of smaller pieces from the low-resolution simulation of bigger pieces," Smith says.

Growing weeds through cracked sidewalks and streets proved to be more difficult, however. First, rotoscopers lifted people and buildings from the plates, and matchmovers provided a virtual camera. Then, texture painters worked on ...