"It was important to deliver on the performance that Joss was looking for," White offered as explanation. "He knew exactly the Hulk he wanted to bring to the big screen. All of the great moments Hulk has in the film was Joss really guiding us there."
An important element in bringing the Hulk to life was having actor Mark Ruffalo wear a motion capture suit, thus creating a greater connection between actor and CG counterpart. The decision to do so was made by Whedon early on. "He wanted to see Mark Ruffalo in the design," said White, "and that was great for us, because that means we could work with Mark."
A great deal of time was spent capturing all physical elements of the actor, with White and his team doing a "life-cast" of Ruffalo. "So starting every shot from something real, we could then capture that performance and apply it to our Mark Ruffalo digital double, and make sure we were getting the right performance to translate onto the Hulk. That's where an amazing amount of animation has to come in, in order to get that same performance from Mark onto the Hulk."
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As to why there has been such a connection the Hulk, White credits it to good decisions made throughout production when it came to the character, most notably his belief that, from the outset, Whedon had clear-cut ideas on the kind of action from the Hulk that people would respond to. "That shot of him slamming Loki was in there right from the beginning," he offered as example.