Step by Step:
Mr. and Mrs. Smith
Jun 1, 2005 12:00 PM, By Ellen Wolff
Taking CG Camerawork to the Max
Director Doug Liman knows how to show protagonists in peril. The man behind the two latest Bourne blockbusters pulls out all the stops for the 20th Century Fox/New Regency Pictures production Mr. and Mrs. Smith. One shot takes viewers aboard a helicopter ride through a steep canyon as the camera pans the canyon walls in search of a cliff-climbing Angelina Jolie. When the helicopter camera spots Jolie, it pushes in tightly on her — a camera move that appears to be one uninterrupted shot.
It fell to Burbank, Calif.-based Digital Dimension to create a seamless shot out of three distinct pieces — the plate photography from the helicopter; the bluescreen photography of Jolie on a faux rock-climbing wall, and a virtual camera move to link both ends of the shot. “We had to create a transition camera move because there was never a point where the helicopter camera was in the same position that the bluescreen camera was — 15ft. from the cliff and tilted up at 30 degrees,” explains CG Supervisor Jason Crosby.
Digital Dimension, which employs a Discreet 3ds Max/Microsoft Windows pipeline, used Andersson Technologies' SynthEyes software to track both the panning helicopter camera and bluescreen camera. Adding to the degree of difficulty of the assignment was that the helicopter shot was sped up and the bluescreen camera craned up on Jolie and her fellow climber. Armed with the information they would need to mimic those two camera moves, Crosby's team then created a virtual camera move to link them.
“For the first four seconds of the shot we have a CG camera following the path of the helicopter,” says Crosby. “Then for four seconds we made this transition from the helicopter to the bluescreen, and then our CG camera followed exactly the bluescreen camera move. During the transition between the helicopter camera and the bluescreen camera, our CG camera had to lock on to — and make an extension of — every little shake of the bluescreen camera. Our CG had to come down exactly the Z axis of the bluescreen camera move, as if it was riding on a pole.”
It took a great deal of finessing to correct for any perspective shifts on the rock wall behind Jolie as this transition was made. Crosby's team created extensive CG rock backgrounds to make the cliff face look believable throughout the entire shot. They began by building a wire frame version of the canyon in 3ds Max, guided by digital elevation models from the U.S. Geological Survey of the canyon where the helicopter photography was shot.
“That was helpful but the resolution wasn't high enough — I think it was one meter per pixel,” says Crosby. “But at least it gave us a rough kind of shape. Using that and topo maps we were able to get a pretty accurate representation. We could take some liberties as far as making the cliff a little steeper, but anywhere where the CG met the ground we had to match the actual cliff.
“It wasn't typical Southwestern rock. It had lots of crags and overhangs, and it required a lot more geometry to simulate those overhangs,” Crosby continues. “We divided the process into three levels. The most prominent features of rock were done by actual modelers creating geometry. For things that were a little less prominent but still had some size to them we used displacement maps. The finest level of detail in the rocks was done — in terms of texture — with bump maps.”
Crosby's team also created textures out of still images pulled from the helicopter footage. “We chose a handful of frames [from the helicopter footage] that were scanned at 6K, and that helped in creating texture maps, but again there was nowhere near enough detail. It's fine when you're 300ft. away from the cliff, but when you're 15ft. away from it, a 6K scan just looks like a bunch of pixels. Our texture artists really had to do a lot of work in [Adobe] Photoshop creating detail where there wasn't any. We chose our levels of detail based on how many pixels the camera was going to see as it pushed in. If there were 4K scan textures butting up against a smaller area that was covered by a 6K map, the seam between them had to be perfect, so you couldn't see that there was low detail on one side of the rock and higher detail on the other.”
Although there were different areas of detail in the rock, the elements were rendered as one image using Mental Images' Mental Ray renderer.
“It's a pretty complex renderer, but with that complexity comes a lot of flexibility,” says Crosby.
For the 2D work required for this shot, including roto and wire removal, Digital Dimension used Eyeon's Digital Fusion. “Wire removal isn't bad when you've got a straight line, but these wires were casting shadows over the undulating surface of the rocks, and it was very close to camera,” says Crosby.
The final post processing applied to the shot was motion blur, which was done with Chronos software (part of The Foundry suite of tools). Because the helicopter plate photography was speeded up, notes Crosby, “when you speed up footage, you don't get motion blur. We used Chronos to apply it to the entire piece so it all got the same motion blur.”
The final effect is a study in integration, with the camera starting from far away and — without cutting — ending up on a close shot. This “virtual zoom” in some respects evokes memories of the famous Charles and Ray Eames film Powers of Ten. Crosby agrees, “That was mentioned quite a bit!”
|Director -||Doug Liman|
|Visual Effects Supervisor -||Kevin Elam For Digital Dimension|
|CG Supervisor -||Jason Crosby|
|3D Tracking -||Travis Yohnke|
|Lead Compositor -||Leandro Visconti|
|Roto/Wire Removal -||Tammy Sutton|
|3D Artists -||Mitch Gates, Christian
Zurcher, Brandi Johnson,
Federico Rivia, Phi Tran,
Tong Tran, James Coulter
|2D Artists -||Ryan Smolarek, Travis
Wade Ivy, Tatjana
Continue the discussion on “Crosstalk” the Millimeter Forum.