'Hot Fuzz': A Cop Spoof CG Investigation

After mocking horror movies with Shaun of the Dead director Edgar Wright is back with a spoof comedy aimed at over-the-top action movies. In Hot Fuzz (opening today from Focus Features), supercop Nick Angel (Simon Pegg) is so good at his job that he makes the rest of the police force look incompetent. To save embarrassment, he is relocated to a quiet country village, but even there, his unique skills are soon put to a test...

Initially, the movie wasn't considered as a vfx-heavy project by production. "The approved shot count prior to filming was about 45; I think by the time of final delivery, we were at a little over 300," recalls vfx supervisor Richard Briscoe, who led the project at Double Negative with vfx producer Steve Garrad and vfx coordinator Sona Pak. "Most of the shots weren't difficult, but there was a steadily increasing volume of them throughout. All spread over an enthusiastic, but small, core team of less than 10 artists. Due to time constraints, there were very few shots we had the luxury of being able to spend more than a day or two onWe also broke an in house record on this one for the shortest shot ever produced: two frames long!"

Briscoe confirms that Wright was almost always very explicit and sure about what he wanted. Yet, during post, he would often hand over whole rough-cut sequences early on as QuickTtime files, and encourage the team to have fun with them. In general, especially in terms of gore, nothing was "too much" or "too over the top" for the director...

"We had to work within an extremelya limited budget, which meant we had to be pretty inventive," Briscoe notes. "It allowed us very little recourse to using 3D. It was actually rather refreshing to go back to some quite 'old school' methodologies, putting stuff together with filmed elements, often significantly re-purposed from what they actually were. For example, we used water-splash elements colorized for some of the blood, or combined and layered many, many small 'bullet-hit' dust elements together, to get rolling dust clouds."

Creative Blasts

The most demanding vfx sequences of the movie were two major explosions. One was a daytime blast at a police station, the other one a nighttime explosion at a private mansion. For the former, the crew was able to do some actual "damage" at the location, as the building was basically an empty shell. This did allowed the crew the latitude to blow out the windows for some tighter insert shots, but not actually destroy the building. The destruction was primarily achieved with a miniature built by practical effects vendor Artem. The model was shot at a matching angle to the location plates.

"While at the location, we shot a variety of plates and passes, which the miniature was then ultimately composited into," Briscoe notes. "Compositing was initially just a case of bringing all of these pieces together. The real work came in adding, combining and retiming literally 50+ individual smoke and dust elements. Edgar wanted to have the feeling of this rolling, dynamic curtain of dust rushing forward and gradually engulfing us, as debris rains down. This was rather a labor of love for compositor Ian Simpson. We used Shake for all our 2D work on this project."

While the police station explosion was all about dust and debris, the blast at the house was all about fire. The brief called for the mansion to be completely vaporized. Since the shoot was taking place at a real house, the crew couldn't rig anything that might actually touch the building at all. Artem used gas mortars to create harmless large-scale fireballs right in front of the house. The fire elements were shot at up to 96 fps in three passes with multiple cameras. "We had already shot a normally exposed and lit 'clean plate' of the house at night," Briscoe says. "So, for the fire passes, the exposure was set for the fire only and all other lighting was off. This meant we essentially got fire against black and an additional, naturally interactive, lighting pass on the building, combined, which we could then basically screen over the clean plate as a start point. We also shot a series of small decorative trees bursting into flames one after another, used later to help delineate the fire's progress down the driveway toward the camera."

Months later, Double Negative set up a fire elements shoot. For the wave of fire that engulfs the camera, gas mortars were used again, but this time, they fired upwards into a black 'ceiling piece' slightly sloping up towards camera. This set-up produced a fire that rolled along a 'ground plane' surface toward camera, without rapidly dissipating upwards. Shot at high speed, the elements were eventually flipped upside down in the comps, to make them seemingly surge across the ground. The crew also filmed some more generic fireballs going straight into the sky, which would help fill in areas immediately in front of the house, as well as numerous takes on a flaming dummy.

Playing with Fire

In compositing, the first steps were to remove the visible parts of the gas mortar rigs, and create the illusion of the explosion starting inside the house. "We scaled down the principal fire passes, and repositioned them 'behind' the windows through a combination of luma keys and rotoscoping," Briscoe explains. "For the moment of the windows shattering, we extracted pieces from the shoot of the exploding police station miniature, but the vast majority of the flying wood and glass debris was CG, turned around by senior 3D artist Pete Bebb.

"Within Maya, Pete used an in-house proprietary simulation system called 'Dynamite' to subject geometry for the frames and glass (with pre-defined break points) to simulated explosive forces. The effect was slightly offset in time for each window. Further secondary forces were applied corresponding to the position of the principal fireballs, later in the timeline. Crude environment maps built from the location fire passes were then used to give us appropriate lighting for the fragments as they travel towards camera. Some rough geometry, again corresponding to the principal fireballs, meant a holdout could be built-in to allow for many of the pieces becoming engulfed as the fire spread. There were also depth and ID passes to allow for adjustments to focus and lighting in Shake, and a shadow-pass for the ground. To help them read better as glass, further 'glinting' was added to the glass fragments in Shake, by running noise patterns through edge detects, and using these to add more bright spots."

Any unwanted gaps or dissipation in the fire passes shot on the location were hidden using the additional fire elements by layering up and offsetting in time. Additional interactive lighting was added to the building for the moment of emergence and for the extra fire elements. Finally, subtle camera shakes were added, and, in the last shot, a simple tilt up and then down, was applied to the originally static shots.

Blood and Gore for Fun

One of the signature aspects of Hot Fuzz is Wright's use of blood and gore as a comedic element. To this purpose, the practical make-up and special effects were heavily enhanced in post-production. "Generally, the enhancements were very straightforward," Briscoe admits. "We had quite a few blood elements shot against greenscreen from when we did Shaun of the Dead with Edgar, and these were brought into service again. Artistically, it was really just a case of finding the right spurt, squirt, spray or gush, in terms of its trajectory and duration, to fit the shot -- or rather, which could be adjusted and altered to fit the shot. In terms of how much or how high we made a spurt of the red stuff, Edgar would always say 'There's no such thing as too much.' In many ways, the more extreme you make it, the more people know it is stylized and enjoy the humor inherent in how ridiculous it is. It's rather like the (eventually) limbless Black Knight in Monty Python's Holy Grail."

The most time-consuming gore enhancement was a sequence in which a character's head is completely crushed by a falling object. The shot of the actual hit involved a handover from a 'crash' zoom-out shot of the actor, and matchmoving in a static camera shot of a life-cast dummy. The dummy was shot against greenscreen on location. It was held by a practical rig that dropped the object to a pre-set height, with charges set to explode the head at the right moment.

Putting the shot together went in two stages. "We first did a pre-comp, which involved a substantial rig removal, as well as losing some smoke resulting from the pyro charge, and adjusting the color of some of the revealed internals of the head," Briscoe says. "This prepared element was then match-moved into the zooming plate. We did some minimal warping to line up the features of the dummy's head and shoulders, to those of the actor for a handover over the moment of impact. Once this all worked well with added motion blur for the zoom and the keying finessed, there was a round of final enhancements. There were obviously quite a few blood elements added -- some quite explosive and some more spurting in their dynamics -- plus further cleanup of the edges of the neck wound (to better match subsequent shots in the sequence). Finally, we added quite a lot of animated spatter and blood staining both to the masonry piece itself and the wall behind."

For the preceding shots, the falling object was created as a CG element modeled and textured from digital photographs of the actual prop. The accompanying dust and fine debris was a combination of smoke and dust elements with some CG particle work. These shots went through many blocking versions, as the team fine-tuned the choreography and timing of the fall with the director, and created camera moves from some originally static plates.

Creating a Digital Mayhem

Besides the gore enhancements, a major part of the vfx workload involved adding muzzle flashes and bullet hits in the shootout sequences. More than 70 gunfight shots were digitally augmented, a mission mainly handled by additional vendors Baseblack, Machine and Lipsync, with elements provided by Double Negative.

"We ended up doing many more bullet hits than we originally expected," Briscoe observes. "Individually, the shots are very simple comps, adding dust-hit elements, sparks, flying debris, etc. The difference is quite subtle when you just watch one shot. However, accumulatively, when you watch a whole sequence, the difference in feeling is very impressive. The town square shootout, for example, is full of extra little hits scattered throughout, so that it feels like our hero characters really do have it all going off, all around them. The raw sequence has a much safer and more pedestrian feel to it. It was a great demonstration of what a differencehow individual, seemingly very trivial enhancements can make a difference when combined across a sequence. A victim of of theirur own success really, the more of these we did, and the more that they then tangibly improved the sequences, the more Edgar wanted!"

Throughout post-production, Briscoe and his team appreciated that Wright was capable of assessing rough temp versions of shots or sequences, and of providing specific feedback from these. "This saved a lot of time, in not having to get things too polished when we were still exploring possible directions or blocking timings," Briscoe concludes. "Hot Fuzz was never going to be a project to employ groundbreaking digital techniques anyway. It was always going to be more about adding a lot of value in invisible ways, working to adopt and blend in with the very distinct visual style that Edgar employs."

Alain Bielik is the founder and editor of renowned effects magazine S.F.X, published in France since 1991. He also contributes to various French publications, both print and online, and occasionally to Cinefex. In 2004, he organized a major special effects exhibition at the Musée International de la Miniature in Lyon, France.