Cinematic horror is rife with tales of the infamous Count Dracula, but few of them dwell on the bloody terror of his "better halves," or vampire brides. But in Van Helsing, the vampire brides abound, and the bloodthirsty creatures were among the most complicated visual-effects challenges the film presented to artists at Industrial Light & Magic (ILM).

"The brides are portrayed by actresses, but at certain points they sprout wings and fly, and [director] Stephen Sommers didn't want them to be entirely computer-generated," says ILM's Scott Squires, who co-supervised Van Helsing's visual effects along with Ben Snow. "He wanted to make sure the actresses' faces came through."

As a result, the ILM team developed a hybrid of live-action photography and motion-capture elements. "After Ben and I discussed some ideas with [animation supervisor] Daniel Jeannette, we decided to photograph the actresses' heads against bluescreen and digitally create the rest of their bodies, which were fairly human except for the wings," says Squires. "When cinematographer Allen Daviau [ASC] settled on the new Kodak [Vision2 500T] 5218 film stock, we shot a test in the fall of 2002 against bluescreen and determined that it would work for effects shots. On location, Ben and I guided the crew on the photography of the blank plates into which we would later add flying or transforming brides."

The location, a Transylvanian village, was actually a huge exterior set built outside Prague in the Czech Republic. Sommers wanted the vampire brides to swoop out of the sky like harpies, attacking the hapless natives. In addition to shooting wide shots and close-ups of actors and complex stunts with four cameras to maximize editing options, the filmmakers also employed a sizable Cablecam rig to capture the brides' points of view and the background plates to which the creatures would later be added. "It was the largest Cablecam setup ever done," says Squires. "They ran two trusses between two sets of huge cranes at each end of the village and then suspended the camera between them on a moving pod. There were days when they shot four effects shots at the same time, and things would get a little crazy when we ran back and forth to make sure we had the correct match-move data."

Once the village-attack footage had been edited, Squires' team plotted the match-move data and added rough animation of the brides into the plates for Sommers' approval. But replicating the camera moves and working out the creatures' flight patterns was the easy part. The greater challenge was essentially reverse-engineering every shot to determine the best way to film the actresses' heads while motion-capturing the movement of their bodies to drive the CG animation. Trying to mo-cap and photograph the actresses at the same time, Squires recalls wryly, "was an interesting twist."

First off, the demands of motion-picture photography and motion capture are almost completely at odds. The conflict stems from the need to light for bluescreen without voiding the mo-cap data. "The big problem is that you normally mo-cap in a darker environment using optical sensors that reflect light into special video cameras, but that won't work if you're in a fully lit bluescreen environment," explains Squires. "So by working with Daniel, our mo-cap department came up with the solution: they custom-built infrared emitters into specially made bluescreen outfits. You wouldn't see those little LEDs glow on the set, but to our mo-cap cameras they were much brighter than anything else in the scene. We did a number of experiments with 5218 to make sure we could keep the light levels that Allen wanted to achieve."

Squires set up each shot based on the timing and composition of the rough animation that Sommers had approved. Though a few setups required two actresses, the ILM team would typically shoot one bride at a time, with the actress either standing on a platform or suspended on a wire rig against bluescreen. "We would have somebody in a doghouse up above rotating her yaw axis, and/or somebody dressed in a blue outfit holding onto her legs, helping to move her up and down," recalls Squires. "Stephen was able to direct the actresses as if it was a live-action shot, and afterwards we could do a real-time composite so he could check their actions in context."

The easy part was lighting for the single motion-picture camera, which was always mounted on a crane or dolly. "Allen Daviau lit the bluescreen evenly with floor-mounted lights and then was able to light the brides so they would fit into the plates," says Squires. "In most cases, the background images were shot on overcast days - or sunny days made to look overcast via postproduction effects." Because the goal was to marry the actress's head to her digital body, framing was critical to creating a seamless blend between actress and mo-cap animation. "We set up the film camera so it would allow for the actress's entire rotational axis," says Squires.

Making sure that the mo-cap data flow was not obstructed by lighting instruments, flags or silks was a bit tougher. "Normally you don't want to block any of the mo-cap video cameras that feed all that data into our mo-cap computer," notes Squires. "But because we were lighting a true shot, some of our mo-cap cameras would be blocked by lights or gear. We therefore set up multiple mo-cap cameras in a ring down below and another set of cameras at the height the actress would fly. Instead of using six cameras, we went with eight or nine so that if certain actions were blocked on one axis, we could capture them from another axis."

Although the brides' arms and legs were animated using the mo-cap data, their wings were entirely hand-animated. Thanks to some careful planning, the hybrid brides worked, adding another tool to the array that ILM uses to create believable humanoid creatures. "As soon as we saw the first couple of hybrid shots, we said, 'Wow, this was really worth it,'" Squires concludes. "It was a lot of work, but it adds so much life and so many nuances to the characters."