They’ve been giant and deadly; they’ve been chatty and contemplative; they’ve been acrobatic and futuristic. Robots in movies have served all kinds of functions in becoming an important part of the cinema landscape. So when filmmakers place a robot at the center of their work, the way it looks and behaves compared with those that have come before must be considered.

That was the case for Alex Garland, the British novelist (“The Beach”) turned screenwriter (“28 Days Later”), who is making his directing debut with the science-fiction film “Ex Machina,” due April 10. His addition to the robot canon is Ava (Alicia Vikander, above), a sleek, very humanlike artificial intelligence created by a reclusive Internet mogul (Oscar Isaac). Ava is the subject of an experiment to test how well she conveys human qualities.

As Mr. Garland wrote “Ex Machina,” he mulled what Ava’s design needed to get across. “She had to look, in a completely unambiguous way, like a machine,” he said by telephone from London. “If she looked like she might be a human in a robot suit, then it would introduce into the film the idea that she may or may not be a machine.”