Double Negative produced the largest number of IMAX shots for The Dark Knight and its work included the bank heist prologue. All images ™ & © DC Comics. Courtesy of Warner Bros.

In comic books, superheroes generally battle one villain at a time. But on the big screen, it seems that two major baddies are a minimum to satisfy audiences. The Dark Knight, now playing from Warner Bros., is no exception as Batman is opposed by the Joker (a haunting performance by the late Heath Ledger) and Harvey Two-Face (played by Aaron Eckhart). Both characters had already made an appearance in the Batman film saga. In 1989, Jack Nicholson portrayed an unforgettable Joker in Batman, wearing a striking make-up designed by Nick Dudman. In 1995, Tommy Lee Jones played Two-Face in the not-so-well received Batman Forever. The actor wore colorful make-up created by Rick Baker.

This time, though, director Chris Nolan wanted a completely fresh approach. The Joker was realized via evocative facial paintwork associated with subtle prosthetics work. For Two-Face, Nolan decided to break new ground. "This character was one of our major vfx challenges," recalls overall Visual Effects Supervisor Nick Davis. "Chris was not interested in going the traditional make-up route. He felt that it would be an additive effect, rather than the subtractive effect that he felt the character required. So, instead of adding a layer of material to the actor's skin, we actually removed the skin digitally. It allowed us to reveal the tendons, the cheeks, the eyeballs and to create unique textures. The challenge here was that we were dealing with one of the main characters, and that the digital make-up would be seen in full close-up, including in dialogue scenes…"

Since the technique was introduced in such movies as Deep Rising and The Mummy, digital prosthetic make-up has become increasingly popular with directors looking for innovative character designs. The task to push it one step further on The Dark Knight was assigned to Framestore in London. In-house VFX Supervisor Tim Webber oversaw the project with VFX Producer Lorna Paterson, CG Supervisor Ben White and 2D Supervisor Jonathan Fawkner. The team used a variety of software, including Maya, XSI, Mudbox and in-house tools for modeling and animation, PRman for rendering, as well as Shake or Nuke for compositing. The all-important tracking and matchmove work was carried out in RealViz Matchmover and Movimento.

Digital Make-up
The design process started with concept art. "As soon as we agreed on a general direction, we hired sculptors to create full size maquettes that allowed us to study the design in three dimensions from all angles," Davis says. "Once approved, the maquettes were sent to Framestore to be digitized and further refined in 3D."

Framestore's White notes that the key to the Two-Face project was to get enough detail into the CGI to give it realism. "In doing so, we worked at much higher texture resolution than we normally use. We also rendered our CG work at 4K, even for the regular 2K anamorphic shots. A very large number of texture layers were needed, and displacement maps from Mudbox were combined with bump maps and displacement maps painted in Photoshop. It really took a significant amount of work to get it right."

The task of capturing Eckhart's performance was a major consideration, as the crew needed to do it on set as shot by the main unit camera, rather than in a separate motion capture session. After testing, Webber and his team opted for a video-based motion capture technique, shooting at 48 fps from several digital witness cameras positioned on set. Later on, when an individual marker was tracked from each witness camera, the position in 3D space could be triangulated. By doing this for all the markers, the performance could be recreated in 3D.

Two different type of tracking markers were used. "The larger primary markers were retro-reflective material to be visible in low light levels, while smaller secondary markers were applied as black make-up dots," White explains. "Because of the logistics, it was sometimes impossible to get many witness cameras in place -- for example, when the action was taking place in the back seat of a car. This made the job of tracking and positioning our CG face even harder. Despite this, there were several parts that needed to be animated by hand. It included the subtle muscle motions when tensing up, and also the animation of the CG eyeball."

While part of the team was handling Two-Face, another part was hard at work on digital environments and CG doubles. Much of this work focused on a sequence set in Hong Kong, where Batman jumps from the very top of a building and glides though the air using his cape. In addition to a CG Batman, Framestore needed to create two full CG skyscrapers that would be seen at IMAX resolution and from close up. "This presented a particular challenge, as the room interiors would be seen from such range that the use of 2D texture cards behind windows would not suffice," White says. "Instead, we used photogrammetry techniques to help model and texture the room interiors. We then created a shader toolkit, allowing us to control the position of each office within the building and adjust the lighting, making sure there was enough variation to create a believable effect. Tiled vista plates of the surrounding city at night were shot from helicopter, and these were stitched together to make a moving panorama."

The sequence ended up as a combination of partial and full replacements of the main buildings and surrounding city, with several shots fully digital.