In the sixth Harry Potter film – the Half-Blood Prince – things have taken a dark turn, with Draco Malfoy now a Death Eater and the horcruxes starting to become important. It was also the most expensive Harry Potter movie, with a budget of $250 million. A fairly large portion of both time and money was spent getting just one special effect right – Dumbledore’s tornado of fire which he uses to rescue Harry from the Inferi.
In the sequence, Harry and Dumbledore have traveled to a magical cave in order to retrieve a horcrux (which contains part of Voldemort’s soul). Dumbledore is forced to drink a potion which greatly weakens him, and Harry tries to fetch him some water.
However, under the water, lie the Inferi – zombie-like creatures, who start to swarm him and drag him under. Dumbledore manages to find the strength to conjure fire – the only thing that destroys them. Harry is seen rising to the surface, which is covered in fire and it was this meeting of fire and water that provided such a challenge to ILM, who were in charge of creating the effect.
“We collected a bunch of references, including flares that burn underwater, and showed them to the Potter folks,” said visual effects supervisor Tim Alexander, speaking in 2009 to Wired. Once Half-Blood Prince director David Yates signed off on a visual template, ILM deployed supercharged Linux machines, each loaded with 16 processors and 4 gigs of RAM. “We emulated all these fire parameters: heat ripples, smoke, buoyancy, viscosity, opacity, and brightness,” Alexander said.
Processing the massive particle simulations for the 100- by 300-foot firewall was burning up days of data crunching for each frame. So computer graphics artist Chris Horvath spent eight months obsessing over a faster way to conjure impressive flames. “Chris figured out that a lower-resolution particle set still had a fluidy flow,” Alexander said “The effect looks as if you sprayed propane and then lit it.”
Check out our guide to the best Harry Potter characters and the best Harry Potter villains.