Climax was shot in 15 days in an abandoned school in Paris. Although Noé conceived a basic story, and gave the cast ideas as to where the story and characters could go, he did not write any lines, and let the cast improvise the dialogue and most of the situations in front of the camera; there were no rehearsals, and only the premise, the characters' basic personality traits, and the early dance scene had been planned beforehand. He stated that when the cast asked him for a script so they could learn their lines, he answered, "No, just come to the set and do whatever you want, I’ll never push you to do anything against your will and if you have any ideas please tell them to me." Noé did give several ideas to the cast, but let them be free to follow them or not: "I knew the start and the end point, but I didn’t know the in-between. For example, initially I thought Sofia Boutella’s character, Selva, would end up with a boy, then I thought maybe it could be a girl. When I met the Russian girl dancer and I asked Sofia if she minds ending up with her, she didn't... so the whole thing was quite organic. Then I didn’t know how the story of the DJ would end... oh maybe he ends with the young dancer... But everything was shot in chronological order, which keeps the door open for any kind of re-writing." He stated that "The mood on set was so joyful and friendly. People were not getting wasted. I asked them what you would enjoy doing in the movie? How would you want to shock an audience? I would never ask them to do, what they would not like doing. Tell me who you want to kiss? Who you want to smash? Who you want to insult? And I would ask the other person, would you mind if this person wants to do this or that. And of-course the reciprocal person was welcome to [propose] anything."
