While doing his press tours for his most recent movie Dawn of the Planet of the Apes Motion Capture god himself Andy Serkis spoke with The Daily Beast about The Avengers: Age of Ultron. If you don't know Serkis came onto the next Marvel film as a consultant to exclusively help Mark Ruffalo mo-cap The Hulk! He goes onto talk about helping Rufflo feel more like the Hulk while motion capturing:
“The difference for Mark [Ruffalo] this time around is that the Imaginarium, which is our performance-capture studio in London that’s providing all the performance capture for the Avengers movie, is providing education, Previously, he would’ve walked onto a set and you’ve got Thor and all the other characters in their costumes looking magnificent, and then you’d have Mark in a grey motion-capture suit playing this enormous character, so it’s about giving the actor the right atmosphere and credibility for the performance, which we did in a number of ways. We had to educate the director that the actor owns the role, and what you get on the set is what you should be aiming to put into your cut as the final performance—with the rendering coming later on.”
He went onto say:
Also, we worked with Mark in really grounding him and playing with the digital avatar before going on set so he could see himself as the Hulk before going onscreen, and we put weights and inhibitors on him to give him the sense that his arms were these big, giant wrecking balls, and so that his biceps wouldn’t intersect with his body. We equipped him. We also gave him a sound system and pitch-modulated his voice so you could hear the enormous Hulk roar coming out of these speakers, so the crew would go, 'Jesus! That’s Hulk on set!' It gives Mark the sense of feeling better, and if he feels better, then he’ll be more comfortable in the performance.”
It was confusing for a while if he was simply a consultant on the film behind-the-scenes or if he also has a role on the film. He goes onto confirm he does also have a role on the film but he isn't saying what! They asked if he was he physical Thanos with Josh Brolin providing the voice but Serkis goes onto deny that character as well as denying playing Ultron himself since James Spader will motion-capture and voice that character:
“Um…I’d have to deny that character at this point, But I am playing a character. I was really thrilled that Whedon asked me to be involved. It’s fantastic. I’ve had a ball working with them, both as performance capture consultant through the Imaginarium, but also being asked to be in it. I can’t say anything more!”Now while he said that "at this point" he is not Thanos that does not mean Joss Whedon won't bring him back in the Avengers 3 given Thanos is only rumored to have a small role in Age of Ultron.
The Avengers: Age of Ultron hits next May