Effects house Double Negative cooked up a desert storm for the special effects in blockbuster movie Sahara.

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Master explorer Dirk Pitt (Matthew McConaughey) takes on the adventure of his life when he embarks on a treasure hunt through some of the most dangerous regions of North Africa. Searching for what locals call The Ship of Death, a long lost Civil War battleship filled with gold, Pitt and his wisecracking sidekick (Steve Zahn) use their wits and heroics to help Doctor Eva Rojas (Penelope Cruz) who believes the ship may be linked to mysterious deaths in the very same area…” 
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That takes care of the plot – let’s get on with the effects. Double Negative (DNeg), a Soho effects house with more than 30 feature films to its credit, landed the job of bringing the sand-yachts, explosions, and duststorms to the big screen. 
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“We were initially approached by VFX supervisor Mara Bryan, who we’d worked with before on a number of James Bond projects,” says Frazer Churchill, VFX supervisor at DNeg. “Looking through the boards was exciting because it was obviously a high-octane action movie, and all the action sequences involved serious military hardware.”
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As the title suggests, most of the action takes place in the desert, which presents its own set of difficulties, says Churchill. “Sand, dust, smoke and bright desert daylight conspired to make production pretty tricky. This coupled with lots of moving camera shots in frantic battle situations created a lot of challenges for our effects team.”
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Because of the unpredictable nature of the desert conditions, the schedule had to stay flexible. That meant Churchill was in Morocco for the duration of the shoot – February to April 2004.
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In total, DNeg completed 185 effects across eight sequences including an explosion in a blast furnace, a land-yachting sequence, a cave full of toxic waste, a Tuareg village, helicopter chases, and the powerful opening sequence.
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<h2>Explosive</h2>
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Deserted

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Out in the desert, things got exciting. All the scenes in the desert, including a land yacht sequence, and bomb alley sequence, where the helicopter is chasing after the heroes, provided some challenging rotoscope work. 
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Cook says: “On the shoot, they had a huge number of vehicles and tanks, so there were tracks everywhere. Additionally, the land-yacht was operated by a stunt driver in a go-cart beneath the plane, which had to be removed in every shot.
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“Most of the shots were tracked with Boujou, which worked extremely well for most of the shots. A handful – in which the camera was travelling quite fast over bumpy terrain – required a lot of manual tracking in 3DEqualizer. Then we broke the shots up into groups based on how challenging they were. 
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“For simple aerial shots where the camera didn’t travel large distances, we de-grained and painted-on 4k scans from the BG plate that we simply re-projected onto the matchmove geometry. 
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“The data provided from Boujou was so accurate that it had unexpected advantages. A few of the desert shots were shot after the sun had fallen behind a cliff face, which caused continuity issues. So we replaced the cliff with one from an earlier shot with very little extra work.”
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The helicopter was photographed extensively in Morocco, which lead 3D artist Becky Waters used as the basis for modelling and painting the CG helicopter. “Once we’d developed controls for the chopper, we could place it in any situation and light it accordingly, which gave Becky the flexibility to invent shots that weren’t storyboarded,” explains Churchill.
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Cook adds: “The helicopter was modelled in Maya, and painted with Deep Paint 3D and Photoshop. It was animated in Maya, and rendered with Pixar Renderman. We used HDRI (High Dynamic Range Imaging) environment lights to add realism, which involves shooting HDRI environment spheres at several different exposure settings.”
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“In the final analysis,” says Churchill, “when VFX shots intercut with the live action so seamlessly to create great action sequences, it’s one of those jobs where the effects support and enhance the story, and should go unnoticed.”
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