ILM relied on Ruffalo's performance in animating the Hulk, down to the pores of his skin and gray temples. All images TM & © 2012 Marvel & Subs. www.marvel.com

Onscreen chemistry was not only important to Joss Whedon for his vision of The Avengers (including well-placed humor to lighten the load) but also getting the Hulk just right because he's the wild card. It turns out the third time's the charm for the Big Guy in this Marvel extravaganza. In addition, Whedon wanted a few tweaks for Iron Man as well considering he's the lead superhero.

ILM, if you recall, previously worked on Ang Lee's Hulk, but this was a far less cartoony rendering, according to Jeff White, ILM's visual effects supervisor. "We really wanted to utilize everything we've developed the last 10 years and make it a pretty spectacular Hulk," White suggests. "One of the great design decisions was to incorporate Mark Ruffalo into the look of him. So much of Hulk is based on Ruffalo and his performance, not only in motion capture and on set but down to his eyes, his teeth, and his tongue. We collected a huge amount of data and, thankfully, Mark is just the most agreeable person for the series of trials we put him through. We did many different types of image capture and he did a life cast of his head, hands and feet for us. Every pore and every blemish came from Mark, even his fingerprints. It was great not having to make everything up.

Whedon talked a lot about anger and rage at the beginning of the project and what they mean. Ruffalo took inspiration from The Incredible Hulk TV series, which he watched with his son. "Poppa, he's so misunderstood," Ruffalo's son observed.

"There's a moment when [Bruce Banner] consciously makes the decision to transform into the Hulk. There's something really powerful about that," White adds. "Our Hulk not only looks really good around the eyes but also has body hair, arm pit hair, nose hair. We knew we were going to have a lot of close-ups, and so it had to be more than just CG skin. We added beard stubble and salt and pepper graying around the temples to match Ruffalo."

Mark Ruffalo got inspiration from the original Incredible Hulk TV series and his 10-year-old son as a force of nature with regard to temper tantrums.

The other quality that Whedon wanted to emphasize was a wrestler physique and vibe. Yet the Hulk has his soft spots, too. He's actually got a bulge around the waist. White calculated a rough body mass of 1,000-1,600 pounds. But when the Hulk gets angry there was lots of room to pop the muscles and veins and see all of that flexing happening.

Also key was making the Hulk a lot less saturated. "It's a more believable skin tone green," White says. "We kept pulling back on the saturation because he would come out of the box very vibrant. He's got to stand next to the other Avengers and look natural."

Indeed, the animators got the mass right along with his facial expression. "You're working in Maya in very low-res and he's got a huge brow and bushy eyebrows," White continues. "But his expressions were lost when we rendered it because the brow would cast a lot of shadow over the eyes. Just a few pixels up or down of the eyelid made such a difference if he felt angry or surprised. There were many rounds making sure the performance came through during rendering and compositing.

ILM used a new procedural shading program that provided the TDs greater control of skin qualities.

"The Hulk was built with our first procedural shading project in which the TDs had control of the skin qualities in different areas and we had the ability to dial up or down dust or scorch levels per shot to alter the look depending on the [mayhem]. Also, when we first started lighting him we took a traditional approach for us with a lot of rim lighting and contrast, especially in New York City. But he stood out above the other Avengers too much, so he wound up flattening out his lighting. We worked with the shadowed, top-lit look and added lots of kicks and rims on him. One of the trickiest aspects was dialing in the sweat level. We wanted him to feel sweaty but not plastic. We utilized beaded sweat (with a lot of breakup) rather than the broader sheens to stay away from the plastic look. The jumping and crashing and environment interaction needed to be believable."