The off-world scenes were filmed on an interior sound stage, using occasional lens flares and off-camera fans to simulate weather. A matte painting by the in-house visual effects department later served as a sky replacement for the used greenscreen. The Vancouver-based company GDFX was responsible for almost all visual effects shots, some of which were re-used within the episode to save money. Other visual effects clips were re-used from previous episodes. "Window of Opportunity" was the first episode to feature a rear-screen projection in the briefing room. To speed up the shooting process, scenes were filmed in thematic blocks instead of in a story-chronological order, and short sequences were re-used to help the audience with a visual recall in new scenes. Sound effects were later added to give the wooden altar prop the impression of being made of stone.