Aiding the invasion in Battle: Los Angeles

In Battle: Los Angeles, the Californian city once again finds itself under attack from alien invaders. Visual effects supervisor Everett Burrell and an army of effects artists wrought havoc on the city as well as realizing the other-worldly warriors.

Seeking to establish a grittier, street-level kind of invasion flick, director Jonathan Liebesman initiated a three minute test to present to Columbia Pictures in order to greenlight the film. With the help of Burrell and SPIN VFX visual effects supervisor Jeff Campbell, the director shot scenes of Aaron Eckhart and other actors dressed as marines mounting an operation in what looked like a bombed out building – actually an office building under construction. “We ran around with a RED camera and smoke machines and made it very hand-held with a lot of zooms,” says Burrell. “We added in a bunch of effects over about a month and a half. Then Jonathan cut it together and put some music to it and showed it to Sony, and that’s how the film got pushed along.”

Production shot mostly in Shreveport and Baton Rouge, Louisiana, with special effects duties overseen by Stan Parks for large-scale destruction and explosions and makeup effects by Joel Harlow. Several vendors contributed to the film’s more than 1000 visual effects shots, including Cinesite, Hydraulx, SPIN VFX, The Embassy Visual Effects, Shade VFX, Luma Pictures, Soho VFX, Intelligent Creatures, Matte World Digital and Modern Film and Video. An in-house team nicknamed the ‘garage band’ of about eight artists also completed shots of tracer fire and various fix-its, working closely with editorial to provide temporary effects as the film was cut.

 

An early mandate from the director was that the film would feel particularly frenetic. “I gave all the visual effects companies a big synopsis of what to expect and the first thing I said was that there was going to be a lot of handheld, and therefore a lot of camera tracking and roto required,” recalls Burrell. “Jonathan wanted to keep it almost like it was a Vietnam War film where you see the enemy off in the distance and you only see shadows and shapes. The less you see it, the more you’re intrigued.”

Designing the aliens

Character designs for the film’s extra-terrestrials – made up of human-like bipedal infantry aliens and a floating commander alien with an elongated body and multiple legs (inspired by the probe both on Hoth from The Empire Strikes Back) – were led by artists Paul Gerrard and TyRuben Ellingson. “Jonathan’s mandate was that the aliens had to move like marines,” says Burrell. “They had to relate to each other like soldiers, not just running around like insects. They were very human-like in their movement, which made them disturbing. They’re aliens, for sure, but they’re not climbing on the ceilings or jumping 40 feet. They had to follow the rules of earth gravity.”

Persistence of Vision Entertainment embarked on a significant previs effort between March and September 2009 for the film’s major effects sequences. A motion capture session for the aliens was also carried out at Giant Studios, and shared with each of the vendors. Mo-cap actors sometimes wore special shoes and inserted their arms through PVC pipes to enhance the rigidness of the alien performance. On set reference for the aliens came from macquettes built by Spectral Motion.

Hydraulx, under visual effects supervisor Bill Kunin, modeled the aliens in Maya for its work on the freeway attack sequence, and shared the assets with other vendors for various shots. “We did some tests for the animation to see whether they should be very creature-like or human-like,” says Kunin. “Ultimately, Jonathan wanted it more like a marine in terms of their tactical moves, so we mixed the mo-cap data with keyframe performance to get the right look for our shots.”

Cinesite worked on shots of infantry aliens and the commander alien, a decidedly different creature. “He kind of levitates, sort of like with mechanical squid legs,” notes Cinesite visual effects supervisor Ben Shepherd. “He sometimes moves a little squidish and spiderish, moving with a thruster. He was in a dark and dingy and steamy sewer, so we made him a bit more waxy and slimy, whereas all the other aliens are always perceived as much more dry and even more dusty because of all the grit and dirt and gunpowder.”

In addition, SPIN VFX brought to life a practical alien for an autopsy sequence in the film – crucial to discovering that the aliens are full of water and may have a weakness. “We added a CG eye scanner, CG ears and gears, a vibrating bladder-type mouth, venting steam, and CG tentacle legs,” says Jeff Campbell. “We had a cyberscan of the alien dummy to use in the aide of object tracking. The alien body parts were so organic and hard to line up to the scan that we ended up building our own geo for RealFlow fluid sims. We designed and built a CG water-pumping heart, which burst when stabbed by Aaron Eckhart’s knife. In order to make it interact with its surroundings the water was half CG and half practical.”

Invasion!

The film’s first big scene takes place as the aliens arrive in Los Angeles and commence their attack. Cinesite created large scale views of the destruction brought on by the strange beings is apparent as marines – sent in to help civilians evacuate the area – fly via helicopter from Camp Pendleton to Santa Monica and witness the destruction. One of the signature effects in the film occurs as alien meteorites crash-land, but not before leaving massive smoke rings in the sky. The effect was created in Maya Fluids, based on a real practical explosion observed by the crew while filming in Louisiana.

Click here for an fxinsider interview with Cinesite about their work on the alien smoke rings – exclusively for fxinsider members as our way of saying thanks for your support.

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For other shots of destruction and combat action, Cinesite had to model and match various military vehicles. “They had three live action CH-46s and one Super Cobra and one or two Huey choppers,” explains Cinesite’s Ben Shepherd. “So we had to populate the whole of an airfield with landing vehicles, CH-46s buzzing the tower. Basically, any time you see an airport there were only ever three real helicopters and everything else is our work.

 

 

 

 

 

Helicopter plates looking down on LA and plates of real CH-46 craft flying along the coast were shot, and then significantly augmented by Cinesite, the studio filling the scenes with general destruction, smoke plumes, numerous vehicles, people, tracer fire and even shockwaves.

We’d always be in one live action helicopter looking at two other live action choppers,” says Shepherd. Then we’d populate the sky around them – we had military advisers telling us how they moved and about the flight formations. The main close-to-camera helicopters were usually always live action. Then we’d have another say 12 in the background flying in trios.”

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“We had an excellent LIDAR scan of the whole set and good survey data. The majority of the shots actually tracked quite well. There were lots of crash zooms and changes of focal length, all of the things that most matchmovers say never do! For tracking we mostly used 3DEqualizer, but we did have some shots where nothing would do it, and had to use Nuke to do camera tracks. A lot of the problems were actually caused when there wasn’t too much movement and there was more like just a

focal drift in it. We had such good survey data, so once you knew what the world was doing, you could work out what the lens was doing.”

For hard body modeling, Cinesite relied mostly on Maya. “We had to destroy all the assets as well,” notes Shepherd, “so some of the damaged vehicles were turned into nCloth and we literally shot them to get rips and tears into them. One thing we used to say was that every shot had to have aliens and helicopters and every shot was huge. When you see some of the scope of the shots, we’ve got damage all the way to the horizon.”

SPIN VFX also created effects of the aliens swarming from the sea, seen through a TV camera crew’s disrupted video signal, and also shots of soldiers investigating the aliens’ behavior from a rooftop vantage point. For that sequence of 35 shots, SPIN built a 280 degree multiplane cyclorama to insert into bluescreen photograph, adding riflescope POVs of an alien ship dropping cargo.

The freeway battle

Hydraulx tackled the film’s freeway battle, completing about 100 shots, in which a group of soldiers is ambushed by infantry aliens. The sequence was filmed in Shreveport, Louisiana. “They shot this on an on-ramp to a freeway that they shut off,” explains Hydraulx visual effects supervisor Bill Kunin. “Basically we roto’d the plate and added LA-style buildings, palm trees, roads and general destruction. We had a LIDAR scan of the freeway and we built some proxy geometry for buildings and then had a two-and-a-half-D solution for placing things in. So then when we did the camera track, everything popped into place and scale was all correct.”

The aliens also storm the freeway with the aid of a two-legged moving weapon that became known as the ‘Walking Gun’, a piece of artillery based on a real device called the Big Dog. “We had a couple of YouTube videos of this,” says Kunin. “It was a strange robotic machine that walked and ran weirdly. If you pushed it over it was able to regain its balance and continue walking. Jonathan never wanted anything that looked too much like it came out of the assembly line – it was more like a home-built kind of look. We’d throw on a bunch of metal – the more chaotic and more random it was, the better.”

Footage from the world

Shade VFX took on just under 60 shots for the film, including monitor inserts, television footage and set extensions, under the supervision of Bryan Godwin. “A lot of the story is told through the use of television and archival footage and things playing back on screens so we can see what’s going on throughout the world,” says Godwin. “We built and designed the graphics overlays for the different news broadcasts to give a reality to the playback on the screens.”

That work also included the re-creation of archival footage. “Jonathan did a lot of research where he’d look through real footage of attacks on say Baghdad or Afghanistan and he’d find these clips,” says Godwin. “They’d be these really small 300 pixel wide clips, and we would take and re-create some of that footage through matte paintings and compositing and elements in CG to up-res them to 2K first and foremost, but also to change the locations from Baghdad to look more like Los Angeles.”

“A large amount of the work was done in Nuke,” adds Godwin. “We’d take the low-res footage in as a backplate and start up-resing from there and then start painting elements in Photoshop. We took a lot of photographs of downtown LA and re-purposed them into matte paintings to fit into this footage of Baghdad. In some cases, we also augmented that with 3D renders out of Maya.”

Adding in aliens

Luma Pictures contributed around 100 shots, including for scenes in which troops are ambushed by the aliens perched on rooftops in a residential neighborhood. For those sequences in particular, Luma relied on Nuke to create an efficient way of inserting aliens into the shots. “What we decided to do early on,” explains Luma visual effects supervisor Vincent Cirelli, “was that rather than tracking everything in 3D, we created these gizmos inside of Nuke’s 3D and used Nuke’s tracker so we could change position of, say, aliens on rooftops and go through iterations of the shots a lore more efficiently.”

This meant that where camera moves were incredibly fast, less tracking was necessary and instead graphically specific locations on rooftops could be tracked. “We created an alien gizmo that consisted of an alien rendered from a 360 degree view,” says Cirelli. “Based on where you positioned the card in 3D space on top of the rooftop, you would automatically have the appropriately rendered angle of the alien for wherever the camera is pointing.”

Luma’s system allowed for a specific ‘alien sprite’ to be be displayed to the appropriate camera angle that would look not like a 2D sprite but in fact a 3D rendering. “What that allowed us to do was track for very specific areas of the shot, and replay scenarios very quickly,” notes Cirelli. “For example, if they wanted an alien running across the rooftop, rather than having to go in and re-animate an alien running across the rooftop, we could look for our specific alien-running asset and propagate that on the card in Nuke. And based on the camera trajectory, it would associate the right imagery at the right angle that was being pulled up.”

“The whole sequence was all about tracer fire, sparks and damage on cars,” adds Luma visual effects producer Steve Griffith. “So we used this ‘sprite-o-mater’, which was what the guys called it, as basically a library of elements, not just aliens but also practically generated elements.” Alien animation was based on mo-cap reference, supplemented with keyframe work. FumeFX was used for missile trails, explosions and fire, and elements rendered in mental ray.

The gas station

For a scene in which an alien drone and saucer come to grief at a gas station, Burrell turned to The Embassy to build those assets and share them with other facilities. “The aliens have flying vehicles that look very much like flying saucers and can split apart almost like a pizza into many slices,” explains Embassy visual effects supervisor Winston Hegalson. “The slices are called drones and hover around the city and they drop white phosphorus weapons and have rockets to take out various pieces of artillery.”

The gas station sequence was filmed in Shreveport. On set, a small macquette of the drone was used for reference that was later scanned by Gentle Giant Studios, with additional modeling carried out by The Embassy to smooth out angles and add hoses, pipes and battle damage.

Artists then created shots based on previs to mirror a Multiple Kill Vehicle that director Jonathan Liebesman had seen. “Jonathan wanted it to move in a very specific way with a staccato firing method,” noted Hegalson. “It had essentially eight control thrusters around the ship that would actually fire in this staccato pattern. They had it flying around in a cage with randomly controlled jets all the time. If it was flying at speed, it would fly around like a ship, but when it went into hover mode it would have a little difficulty maintaining its lift down the streets.”

“What that brought into it was a lot of additional Houdini-type work,” continues Hegalson. “We had to integrate it much more into the scene, so we did a bunch of Houdini simulations like vortexing dust and papers flying around, rocks moving and flying through the air. So we started with a fairly clean plate, but dirtied it up.”

Our primary software for animation and lighting and rendering is XSI rendered out of mental rayTo create the scene’s mayhem, The Embassy built a two-and-a-half-D matte painting for backgrounds, also integrating ships and other vehicles into greenscreen footage of people trapped on a bus. The studio’s other major sequence involved one of the soldiers sacrificing himself before being taken out by one of the drones. “Our primary software for animation, lighting and rendering is XSI rendered out of mental ray,” says Hegalson. “Houdini is our fx pipeline, and compositing was all done in Nuke. Tracking was all done in SynthEyes. We did a lot of buildings and UVing in Modo.”

Medivac crash

Soho VFX added The Embassy’s drone model into its shots of a medivac Huey helicopter crash. After the Huey gets shot by the drone, it smashes into the ground and explodes. “To realize this,” explains Soho visual effects supervisor Keith Sellers, “we used a combination of live action smoke/explosion elements, and fluid simulations done in Maya.”

 

“One challenge we had was getting the look of the rendered fluids to match with all the live action elements that were comped into the shots. We ended up combining the fluid smoke with some faint live action smoke to get a look that worked in the shots. For the explosion we combined two live action explosion elements together to get the level of chaos that we needed, then augmented that with some CG fire and smoke. The Huey breaking apart during the explosion was done by making a few hero pieces and hand-animating those, then doing some rigid body simulations and particle instancing to get all the smaller debris in there.”

Soho tracked the shots in PFTrack, before bringing the cameras into Maya to render out the 3D elements. ” For adding 2D elements like smoke and dust and fire,” says Sellers, “we brought the tracked cameras into Nuke and mapped each element onto a card which we positioned in 3D space. This let us change those elements very quickly since it was all being handled inside Nuke – which was essential as there were so many layers of smoke and dust in each shot.”

The final battle

A final attack on the alien command and control center was split, in terms of visual effects duties, between Cinesite, Hydraulx and SPIN. Here, the marines find the alien’s central communications resource from which the creatures receive their command signals. They attempt to ‘laser-tag’ it and radio in a missile strike. The initial success of the strike is short-lived, however, when only the top of the large antenna is blown off and the battle continues.

Hydraulx modeled the center based on concept designs, adding extra antennas, solar panel-like areas and increased the size, and therefore threat, of the ship. Cinesite created shots of the soldiers being attacked by a large hovercraft, essentially a gun platform operated by two aliens. “It comes out with a blaze of canon fire with two different machine guns,” says Cinesite’s Ben Shepherd. “We’ve got real fluid turbulence from the ground interaction and lots of dust and debris.” Hydraulx took over as the command and control center rises up out of the ground with drones attached to it and others flying around on suicide missions during the battle.

SPIN completed the film’s final shot, in which the camera pans up to a 30-second long CG scene with a dozen helicopters and two F-18 fighter jets overtaking the camera against a backdrop of a mostly destroyed Los Angeles. “We were supplied an aerial film plate from the Hollywood Hills revealing downtown LA,” says SPIN’s Jeff Campbell. “Production supplied the helicopter asset for us to write the shaders. The matte painting was created in Photoshop and fed into Nuke as a multiplane card projection. The 3D camera track was fed into Nuke and a ton of live action fire and smoke elements were then added. All the animation at SPIN is created in Maya and rendered in RenderMan.”

‘Terabytes of explosions’

“I’m really proud of the visual effects work, but also the mix between the practical and digital work,” says Everett Burrell. “I shot a tremendous amount of practical elements over a period of a few weeks. We’d get a break in the schedule and I’d go out to the desert and just shoot fireballs and smoke plumes and white phosphorous elements. I have three or four terabytes full of explosions that you’ll probably be seeing in every movie I’ll be doing from now on!”

 

All images copyright © Columbia Pictures.