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MillimeterDigital Acrobatics
May 30, 2007 10:28 AM, By Michael Goldman
Inside Imageworks, Spider-Man effects veterans discuss the franchise’s visual effects evolution.
Unique combinations of CG characters with pieces of live-action stunt performances were used to build many of the action shots in Spider-Man 3.
At Sony Pictures Imageworks in Culver City, Calif., as work on Spider-Man 3 winds down, many of the key players behind the film’s visual effects extravaganza (just less than 1,000 shots) are finally starting to contemplate life without the spider. Some, such as Visual Effects Supervisor Scott Stokdyk, have been involved in the franchise in one way or another for more than seven years—since planning for the first movie got underway.
In looking back at the evolution of the franchise’s effects, Stokdyk and his colleagues are naturally proud of how far-reaching the influence of their work has been. As he tidied up a few loose ends on the project, Stokdyk took time to sketch out for millimeter some of the visual effects trends moved forward by the latest chapter in the Spider-Man saga.
“Combining pieces of live-actor performances with CG elements in heavy digital sequences and the degree to which we worked closely with stunt people were pretty important,” Stokdyk says. “The stunt people we worked with have moved quite a bit in the last couple years into computer-controlled wire systems—high-speed winches to move their stunt people around that are all computer-controlled. We learned how to move a camera relative to stunt people and to use extensive previsualization models to provide the production with information from the previz so they can match it with their computerized wirework. I had never seen that before—it borders on motion-controlling people.
“That’s an interesting trend I expect to see carried on—visual effects work that relies heavily on stunts to get bits and pieces of shots we can put together later. In many ways, doing an action shot completely computer-generated nowadays is easier than incorporating live-action elements. It’s not new to have all synthetic shots. But what people in the visual effects community have to be intelligent about from now on is how to incorporate live-action elements into a synthetic world to give you something you can’t get all-CG or all in-camera. That is something big I’m personally taking away from this movie.”
The New Goblin character and his glider were largely all-CG creations, combined with bluescreen elements of actor James Franco for action sequences.
Facial Replacement
In particular, Stokdyk is referring to the degree to which director Sam Raimi wanted Spider-Man unmasked during web-swinging episodes—sometimes forced to battle his nefarious foes in street clothes, in fact. This required an extremely sophisticated facial replacement approach for adding those real bits and pieces to a CG character engaged in heavy-duty action.
“We had to stretch our methodologies to combine stunt work with face replacement work—mixing live-action photography and CG in all sorts of different ways in a single shot,” Stokdyk says. “For instance, in one shot, we had a stunt guy spinning around on a special stunt rig over a bluescreen [standing in for Spider-Man’s alter-ego, Peter Parker], and he gets kicked by a CG [Goblin character] on his [CG] glider, and we then have to transition from that kick to a CG Peter Parker, and then, from that CG Peter Parker, we have to go back to the stunt Peter Parker, slamming into a set piece. So, in the same shot, we went stunt to CG to stunt and CG background to set background to CG to set. Those are the kinds of unique combinations that we were faced with.”
Imageworks’ previz team was central to this process. They would convert an animatic of such scenes into Autodesk Maya-based CG shots, and then turn over the computer models and related geometry to the visual effects team, which, under the guidance of Motion Control Supervisors John Schmidt and Nic Nicholson, would download that data into the computer system for the motion-controlled rig. This permitted the production to shoot stunt people executing various sequences against a bluescreen, and then use the same camera data and movement to film lead actors such as Tobey Maguire performing facial close-ups for the same scene.
Those facial performances were then mapped onto the moving CGI character, and as the sequences were built, the effects team then transitioned seamlessly between stunt shots, CG shots, and combo shots with a unified sense of camera perspective to sell the illusion.
“So, in some cases, we ended up with very long shots you could never photograph in real life, but with an animated character having the real actor’s face,” says Spencer Cook, the film’s animation supervisor. “We also tried to incorporate animation and bluescreen elements of the actors in various combinations. For instance, we filmed [actor] James Franco [as the Goblin] on his glider on a rig in front of a bluescreen, and then we would take that element and put it on a 2D card within Maya in order to move it around and enhance some of what was done on the stage.
“In other cases, we would go from the 2D element, the actual photographic element of the actor, directly into the full 3D digital character. We did lots of that kind of blending from an area where you see the actor’s face, and it’s clearly that actor, and then, through wipes and camera moves and things, you go to a digital character who is flying and doing all the things you could not do with rigging on a real stage. It’s about mixing all that stuff within the same shot. We did that to a far greater extent than what I’ve seen before this project.”
Continue the discussion on Crosstalk the Millimeter Forum.