Mark Spatny, Supervising Producer for Stargate Films, acknowledges that it wasn't the most complex visual effects sequence of the show (that would be Season 3's cleaving of Tokyo—more on that, below), but there are scenes in Heroes' first season that contain a confounding mix of practical and virtual, including an episode in which Claire (played by Hayden Panettierre) battles a radioactive man (no, not The Simpson's comic book character) who burns her to a crisp. (If you're interested, check out Heroes Monday nights at 9:00 p.m. on NBC.)

"We had originally planned to do it practically, with quick cuts, and several Claire look-a-likes in special effects make-up," Mark recounts. "First, we had to get Hayden's make-up right. We work with a great special effects make-up company and they know the difference between, for instance, radiation and electrical burns. They designed a look for Hayden with a shading technique for burned skin that would flake off, and then applied that look to her. She sat in make-up for eight hours!" Once the "Crispy Claire" look was established, the make-up team applied various stages of the look to the Claire look-alikes.

The VFX team did, indeed, fry the cheerleader through a mix of practical make-up and digital double but, thankfully, she was able to save herself through her regenerative powers. Image courtesy of NBC Universal and Stargate Digital.

"But, when we got on location and shot the scene," says Mark, "no matter how much the Claire look-a-likes looked like Claire, they didn't move like Claire—not exactly, as every human has a distinctive gait, almost like a fingerprint." So, after all that work, the practical effect was scrapped in favor of CG. "We came up with a solution that used most of Hayden's performance, and created a digital double for those few, fleeting on-screen moments when she's supposed to be engulfed in flames or charred to a crisp."

A 360-degree laser scan of Hayden was taken "neutral," without make-up, and then several still photos were taken of her as Claire, in hair and make-up, for reference. The team then took the live-action plate of Hayden's performance and, frame by frame, inserted the computer-animated 3D model in exact alignment, "almost like tracing paper," says Mark. Wherever the digital double appeared in the scene, the team applied texture, such as hair and skin tone, to the 3D model. "We use match-move software, like boujou, to make sure the actual and virtual Claires stayed in proper alignment and perspective as the camera and character move." Once the CG character matched exactly, the team could dissolve (an optical effect in which one image seems to dissolve into another) seamlessly between the two.

The Iceman Cometh

The team went from super-hot to stone cold when Tracy Strauss (Niki Sanders' identical triplet, also played by Ali Larter) gives a journalist the cold shoulder—literally, turning him into a human Popsicle® that shatters into a thousand pieces. That scene presented more than its share of artistic and technical challenges.

For starters, what does a human block of ice look like? And how does it shatter in a manner that looks realistic, considering no one has ever seen a frozen human shatter into a thousand pieces? (Remember, Robert Patrick's liquid-nitrogenic T-1000 in Terminator 2 was a machine.) "It all starts with a script break-down," says Mark who, together with Heroes VFX Supervisor for Stargate Films, Eric Grenaudier, reads the script, noting every scene and sequence requiring visual effects shots. Typically, there are anywhere from 80-100 visual effects shots for each episode of the series and Mark and Eric work together, along with their visual effects team, to get them done.

"We have a concept meeting with the director, producer, and other department heads, including make-up, wardrobe, and camera, to figure out the best way to approach the shot," says Mark, who is responsible for budget and scheduling. There are some effects that can be done practically, in camera, on a live set using make-up and prosthetics, for example. "We could have done the ice-man scene practically, with a sculpture," agrees Eric, who is ultimately responsible for the creative look of the effect. "In fact, another show did the same gag [visual effects parlance for a VFX shot or sequence] a few weeks later, and that's the approach they took, but we decided to do it CG."

What does the inside of a human, frozen solid, look like as it shatters into a thousand pieces--and does it really "shatter," or it more "crumble" or "disintegrate?" Image courtesy of NBC Universal and Stargate Digital.

Explains Eric: "First, we shot the live-action plate on location in the parking lot where the scene takes place, right up to the point where Tracy touches the journalist with her new-found power and he begins to freeze." (The journalist was played by William Katt, best known as the super-cute 80's superhero in the sitcom The Greatest American Hero.) Literally, Katt froze at that moment, holding his body very still "Then we took him out of the plate [the live-action footage], and Ali reacted to this empty space as if he were freezing, toppling, and shattering right in front of her." And that's when the VFX fun began.

"We did a 360-degree laser scan of Katt in his character's wardrobe to create an exact digital double that we imported into the 3D animation environment Maya," says Eric. This is the juncture at which artistry and technology really intersect. "It was open to everyone's interpretation, what a human block of ice looks like, and how it shatters," Mark notes. "Should he look as if he's been dipped in liquid nitrogen, or frozen at the molecular level? And, I know it sounds gross, but, when he shatters, is it into thousands of 'ice chips' of human blood, guts, and entrails, or does it look less life-like? And does he really shatter, or is it more 'crumble' or 'disintegrate'?"

According to Eric, the first order of business in the scene was to make the transition from live-action actor to 3D model. "We did this in the first 'frozen shot' of the scene," he explains, "by matte painting a layer of frost, condensation, and ice onto the live-action plate, giving a lot of thought to Katt's skin complexion and coloring, how it would change as his body froze." By the second shot of the scene, "we were into our digital double, who we lit virtually with exposure information captured from the location."

Close Move

Eric and Mark's VFX team uses pre-visualization software ("pre-viz" in industry lingo) so the director and producers can see how the effect will unfold. Clip courtesy of NBC Universal and Stargate Digital. (Click to play. Movie will begin playing once loaded.)

Right-click to download this video clip.

To ensure the lighting of Katt's character—live-action and digital double—is consistent throughout the scene, even as he freezes over, the VFX team used a technique known as high dynamic range imagery (HDRI), which helps accurately render illumination, reflection, and shadow on 3D objects as they move through their environment. "Basically, you use a camera—I use a Cannon SLR 5D," says Eric, "to capture a still scene in as many different stops, or exposures, as possible [typically, five under and five over the key exposure] in order to collect a dynamic range of data that enables virtual light to change as the virtual camera and objects move." A similar technique is used in panoramic photography.

Then various computer simulations of how ice would form on the body were run, starting from when Tracy grabs Katt's character's arm and frost travels across his shoulder, engulfing his face and, eventually, encasing his body. At this point in the process, Mark was thinking a glass-like shatter of the character into big shards would be best. But when Eric saw the simulations, it became clear that he was envisioning something more "like glaciers calving," says Mark, "bigger chunks, with smaller particles. We really had to re-think our approach." When they got the consistency of the shatter correct, there was also the matter of the, um, matter. "Nobody had really thought about it till then, but he's human, so the chunks would be frozen meat and gristle and bone," Mark notes.

"To enhance the CG shots of this human ice block shattering into thousands of pieces, we shot pass after pass of practical liquid nitrogen in our studio, along with chunks of meat, and blended everything together in the computer," says Eric. According to Mark, the first completed sequence was "a little too gruesome, we had to tone it down," but they are both very proud of the result they were able to achieve, especially on the comparatively limited budget afforded television series (in comparison to motion pictures). Thankfully, they had a little more time to plot the complete destruction of Tokyo.