However, it turned out that the virtual New York City during the alien attack of the last third posed the biggest challenge. ILM couldn't shoot principal photography there but sent four teams of photographers shooting spherical overlaps at all the appropriate locations, especially the Park Avenue Viaduct. They shot on the ground every 100 feet and up every 120 feet with a man in a lift moving down Park Avenue. They made close to 2,000 spheres and stitched together 275,000 high-res photographs like a Google street view.
"In New Mexico, we had a 300-foot set of the Park Avenue Viaduct dressed with a couple of flipped over cars," White explained. "They don't care how much exploding you do in New Mexico. And then we projected that onto the buildings and that gets us 60% there. But once you move the camera, everything that's static in a photo no longer holds up. Not only does every window requires its own reflection, but also every window blind needs to be a different height and every room interior needs to be different. We replaced every window from the photography with a CG window and the inside the building contains nearly 30 of our ILM offices that we digitally reproduced.
"And we had tools that we actually developed for 'Rango' in terms of populating the town. And we leveraged those and built upon them in order to populate the environments of all the street signs and cars and planter boxes. One of the benefits of a virtual New York is that we can use that environment to light our CG creatures."
It all comes together in that memorable, iconic shot of the camera moving around the Avengers, who are huddled together and poised for action. It's seamless and not as flashy as the Hulk but effective VFX.