Double exposure.(mocap)

The feature film Van Helsing is full of amazing effects, but from a technological standpoint, none can compare to the groundbreaking motion-capture work by Industrial Light & Magic (ILM).

To create a trio of hybrid vampire brides--characters with the heads and faces of actual actresses fused with computer-generated bodies--the studio developed a first-of-its-kind technique that enabled it to acquire motion-captured data during a live film shoot.

For the sequence, Dracula's brides metamorphose from sultry females to bloodthirsty vampires who use bat-like wings to swoop through a Transylvanian town and attack the villagers. Despite the transformation, the creatures still had to have the same facial performances and look like the actresses, only creepier. The ILM group decided to accomplish this by applying makeup and prosthetics to the head and face of each actress, and then "marrying" the actual head to a digital body to give the team more control over the complex, acrobatic movements that animation director Daniel Jeanette was seeking.

ILM had done this type of work before using a more time-consuming procedure of manually tracking an actor throughout the shots and then replacing the person's body with a 3D version in postproduction--a process that may not extract all the nuances of the performer. This time, with Jeanette's prompting, the group devised a novel technique that allowed it to use motion-capture cameras for acquiring the movements of the actresses, while the film crew simultaneously shot the backplates of the women's facial performances.

Previously, a simultaneous capture like this was out of the question because the bright stage lights rendered optical-based motion-capture systems--which track reflective light from markers placed on an actor's body--useless. And while magnetic mocap systems are not affected by lighting conditions, they can be influenced by metal, such as the film cameras and harnesses that were used in the scene.

To overcome these issues, ILM's principal engineer, Kevin Wooley, developed customized markers using high-powered infrared LEDs that could be tracked by the Vicon mocap cameras ILM was using. Because they worked outside of the visible light spectrum, the markers were invisible to the naked eye--and the film cameras.

The markers were fitted onto customized motion-capture suits worn by the actresses. A main cable fed power to 45 of the special markers through flexible, lightweight ribbon wires, enabling the actresses to move easily. On the set, the actresses--who were adorned with makeup, wigs, and special contact lenses, and completely covered in blue from the neck down to aid in the rotoscoping process--moved with the help of a harness and stunt puppeteer. "It was critical that the [mocap] information be exact when it came time to line up the computer-generated body with the real neck and head," maintains Doug Griffin, ILM's motion-capture supervisor.