This article contains spoilers for Game of Thrones Season 6 Episode 10, "The Winds of Winter."
In what was undoubtedly Game of Thrones' most exciting season finale to date, a handful of prominent cast members went up in literal flames. Having lost all of her allies in King’s Landing, Cersei Lannister ignited the massive cache of wildfire that The Mad King had stashed beneath the Great Sept of Baelor, producing a colossal explosion at the center of King’s Landing. Through a combination of analog camera tricks and a whole lot of complex CGI, the fuse blew during what was supposed to be Cersei’s trial of atonement, seeing the High Sparrow, Mace, Margaery, Loras Tyrell, Lancel Lannister, and about 287 extras consumed by a massive cloud of green flames.
Equipped with an artificial light source and a collection of giant wind blowing machines that shot big gusts of air over the crowd of actors, GOT crew shot the explosion on the set of the Grand Sept. Using the wind and the light, the crew staged the very first moments of the explosion inside the building, before the visual effects started to really take over the image. On set, the episode’s director, Miguel Sapochnik, the man who put together the undeniably excellent "Bastard Bowl," would countdown to the moment of ignition, signified by a shot of air and a flash of white light. At that moment, all 287 extras would fell backwards in unison as the blast’s shockwave passed over them. In the special featurette below, Sapochnik explains, “that was as close to exploding as we got. But a majority of it, 99% of it will all be visual effects.”
Visual effects associate producer Adam Chazen describes the order of events in which the episode’s VFX came together: After the effects team got the storyboard, they sorted out their camera arrangements and the animations, so that when it came time to film, the crew had a fairly comprehensive animatic vision of what that final shot would look like. “Obviously it looks like a video game, but we know what we're going for and how we want it to look at the end of the day,” says Chazen.
The explosion begins with two wooden barrels leaking puddles of the neon wildfire. The actual liquid is a highly fluorescent neon green pigment that was lit from underneath using a UV LED system and lighting trays. The leaking barrels then explode, triggering the row of barrels all the way down the vault wall. One of the show’s special effects coordinators, Sam Conway, describes how they incorporated footage of actual fire into the explosion scene using a camera, mounted onto the tall structure, and pointed at the ground. A controlled flame is shot out of a black flamethrowing device through a sort of funnel, and up towards the camera. Conway explains, “They explode, so then when we do the barrels, we’ve got some pyro set up. Flame always flies up towards you, so you shoot it like that. You’ve got a flame coming up towards the camera. When you see it like that, it’s flame coming down, coming down towards you. And everything else is, um, CG.”
One of the advantages of having full-hour episodes, is that they allow filmmakers the ability to take their time with certain sequences, adding a level of cinematic zest to television series. This was a calculated and carefully set trap, and the Game of Thrones crew set it off with the same calculated precision as Cersei herself.
You can watch every episode of Game of Thrones on HBO.