The mammoth green-screen (which the majority of the film was shot in front of) was housed inside a large industrial warehouse, where the temperatures would drop close to freezing after the sun had set. Cast members (wrapped in blankets) warmed themselves beside small propane heaters in between takes.
Spending long hours in front of the 400 ft. green-screen, caused many of the cast members to temporarily lose their peripheral vision. Actors would run face-first into the screen on a regular basis.