The actor plays the supervillain in the new Marvel blockbuster, due for release next spring.
Brolin said in a new interview that he was shown a six-minute sequence of himself in action – and it left him with his jaw on the floor.
“They [Russo brothers] showed me a little six-minute teaser of a scene that I had done, I was so blown away by how next-level this digital process is and how real it feels,” he told Collider.
“I don’t know how I could be anything but happy.”
The actor plays the supervillain in the new Marvel blockbuster, due for release next spring.

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Brolin said in a new interview that he was shown a six-minute sequence of himself in action – and it left him with his jaw on the floor.
“They [Russo brothers] showed me a little six-minute teaser of a scene that I had done, I was so blown away by how next-level this digital process is and how real it feels,” he told Collider.
“I don’t know how I could be anything but happy.”
He added: “If everybody hates me at the end of it, I don’t know, will it be worth it if it’s a great movie? Maybe.”
Casting news for the film is still dripping out for both Infinity War and its untitled follow-up – for now referred to only as Avengers 4 – with another face from Iron Man 3 rumoured to be aboard just yesterday.
Avengers: Infinity War is out on April 27 in the UK.