White House Down: Method Studios Wreaks CG Havoc
COW Library : TV & Movie Appreciation : Ollie Rankin : White House Down: Method Studios Wreaks CG Havoc
Graduating with Honors from the University of Auckland in New Zealand, Rankin majored in Computer Science. Rankin has brought his VFX skills to Tokyo, San Francisco, London, and now Vancouver to work on different projects.
Method Studios Vancouver created 185 shots on White House Down, including CG helicopters, digital doubles, fully digital and extended partial environments with the White House and Capitol Dome, lots of trees; effects included missile trails, explosions, fire, smoke, building destruction, trees blowing and being shredded, ground impact destruction, water interaction. Oh, and they also did some bluescreen comps.
The film's total number of shots was 900 shots; other houses that worked on the film included Uncharted Territory, Prime Focus World, Hybride Technologies, LUXX Studios, Image Engine, Scanline VFX, with additional VFX by Crazy Horse Effects, Trixter, Crafty Apes, Factory VFX, Fuse FX.
In this article, Method VFX supervisor Ollie Rankin, who worked with Method VFX Producer Christopher Anderson, talks to Creative COW about how Method's crew of 80 artists handled some of the movie's most challenging VFX.
We hadn't worked with [visual effects supervisor] Volker Engel before, but we were quite keen to get some of the work on White House Down. I think the work we did on G.I. Joe: Retaliation and Abraham Lincoln: Vampire Hunter was relevant to the style of work required on White House Down, and we were fortunate enough that some connections in the wider Deluxe family of companies came through and did the handshake between the various parties.
Although we were not responsible for the greatest volume of shots, we did have the most complex shots and also provided the bulk of the 3D asset creation. Volker and Marc Weigert [co-producer/visual effects supervisor] have their own in-house facility, Uncharted Territory, and a lot of the concept drawings and previs came from there. We got involved at the point they needed the CG White House and Black Hawk helicopters.
Initially, they built the pristine, undamaged White House back in September, when they were first working on the trailer, and had to create the damaged South Portico later.
The first asset we needed to get working on was the White House; all the other vendors were going to need our White House asset and several would also need the Black Hawk, the White House grounds and trees and so on.
Another reason why it made sense for us to build these assets is that in our shots they are featured up close so they would be subject to a lot of attention. We built the White House based on a great deal of research and reference photography; there's a surprising amount of information out there about that building.
The attack on the White House begins to show with CG damage inside.
Initially we built the pristine, undamaged White House back in September, when we were first working on the trailer. The bulk of the shots that Method undertook take place after a sequence -- done by Prime Focus -- in which a tank round has damaged the South Portico of the White House. So we had to build the damaged South Portico.
A tighter shot of the CG damage to the South Portico of the White House.
We did all the modeling in Maya and texture painting in Mari, using WETA's elegant expansion of the traditional UV texture space, known as a UDIMs. Not to be confused with UDIMMs, or memory chips, UDIMs are a way of associating different textures with various objects that share the same surface properties, making it possible to greatly reduce the number of surface shaders in the scene.
BLACK HAWKS DOWN OVER THE WHITE HOUSE
We worked on a sequence in which three Black Hawk helicopters fly over the White House and all of them are shot down by the terrorists. Director Roland Emmerich and the production-side VFX team conceived of nearly every possible permutation of a helicopter being shot down in the White House grounds, before deciding on the three different events. Completing these difficult shots enabled us to really push the boundaries of our fluid, rigid body and soft body simulation pipelines.
The sequence begins after the terrorists come into the White House, neutralize the security detail on the roof and position themselves on the roof with snipers and rocket launchers. The National Guard, which has tried and failed to retake the White House earlier on, send in a squadron of three Black Hawk helicopters. To avoid detection, the helicopters fly low, barely above stopped traffic on the streets of DC, hiding among the buildings as they approach the White House from the North. The terrorists spot them and shoot the first rocket; the helicopters take evasive action and circle around, but one by one, the helicopters are hit and go down.
The sequence begins after the terrorists come into the White House, neutralize the security detail on the roof and position themselves on the roof with snipers and rocket launchers.
Meanwhile, Channing Tatum's character Cale has come on the roof and is also fighting the terrorists. The scene ends with Cale in hand-to-hand combat with the terrorist leader, Stenz, who still manages to fire the missile launcher and take out the last Black Hawk.
Combined plates of the actors against bluescreen.
The biggest challenge of this sequence was just how much of it was fully CG. We did every shot in that sequence from the moment of the first missile launch. The bulk of the work was around the CG helicopters, but we also did quite a lot of blue screen work on the hand-to-hand combat and machine guns being fired from the helicopter and the roof of the White House.
Compared to the helicopters we did on G.I. Joe: Retaliation, in White House Down, the helicopters are quite large in frame and it's also broad daylight, so the helicopters undergo quite a bit of scrutiny. Although there are some cutaways of a partial helicopter on a gimbal on stage, whenever you see a full helicopter, it was always CG.
Although there are some cutaways of a partial helicopter on a gimbal on stage, whenever you see a full helicopter, it was always CG.
In most cases, the entire background was also CG since you can't get permission to film that close to the White House. They built a partial rooftop set so all the hand-to-hand combat took place there. But everything off that set is all CG including the White House gardens, CG trees, and a matte-painted background.
When a missile hits the first helicopter, the copter is burning, billowing smoke, and spinning out of control over the White House
Several shots in the crashing of the three helicopters were very elaborate in the number of interacting components that went into them, and they were a big step up for our team in terms of complexity. When a missile hits the first helicopter, the copter is burning, billowing smoke, and spinning out of control over the White House. It crashes through the flagpole and then into a tree and, as it breaks up, it explodes and the blades are grinding up the ground and breaking trees. All these different elements had to interact, which made it our single most involved shot.
There were about 150 rendered elements in that shot, and each element had multiple layers. The White House in the background with the surrounding grounds and trees probably took up 5 to 10 layers. Of those, each one was separated out so they had diffuse lighting, specular lighting, reflected components, all divided out so the compositor could balance them. On top of them were foreground layers.
The helicopter was hand-animated but it required a special rig because it needed to break up progressively as it hit the ground; when the tail rotor hits the tree, it breaks off, creating additional debris.
The way we approached this was to design the animation using a very low-res representation of the helicopter and got one of our top modelers to model in all the crumbled, shattered metal detail. Our rigger then built the rig that allowed all those transitions from an undamaged copter to a damaged one, and the animator redid the animation using that updated rig. The helicopter went to lighting, but at the same time, it needed to drive all the effects that went on. To do so, we cached it using Alembic, an open source format that allowed us to load in Maya and Houdini and even Nuke if we needed to.
Using the Alembic format to cache the helicopter animation meant that we could develop the methodology required for the rotor blades chopping up the tree, which took a lot of time. We had recreated the tree from our generic White House grounds tree library in Houdini, using wire deformers to drive dynamic animation in the branches. Then, with a proprietary set-up, we triggered rigid body destruction from the impact of the fuselage and the rotors. As the helicopter flies towards the tree, there's also rotor wind emanating from it, and the ground is also being churned up by the blades.
From beginning to end, the sequence took six months. It began as a couple of different R&D tasks that has an artist dedicated to each one. In the last 2 or 3 weeks, we had a dedicated team of 15 artists working on this one shot.
CREATING CG TREES
Trees were something else that took a lot of effort, and we underestimated that in the beginning. We went into the show knowing the White House would feature prominently and would be difficult to match photorealistically. We knew the helicopter and all the dynamic effects would be difficult. But we thought of the trees as a peripheral.
At a certain point, as we were building up our library of trees, we realized they're actually quite difficult to do in a believable way. And even though the focus of all these shots is the helicopter or the White House or an explosion, half or more of the screen space is actually filled with trees. They're always there and they deserved a lot more attention than we initially thought they would.
The other tricky thing about trees is that they're always moving. Even with the gentlest breeze, the leaves are fluttering and the branches are swaying. It's amazing how subtle that movement can be. But if the trees are static, your eye immediately knows they're CG.
We developed strategies for moving the trees. One is a technique within Nuke that used procedural warping to make the leaves and highlights flutter. That was incredibly successful when the trees were in the background and defocused. But as soon as the tree came into focus, you could see the gag.
CG crowds at the Washington Monument.
As the helicopter flies towards the tree, there's also rotor wind emanating from it, and the ground is also being churned up by the blade.
We built most of the trees using a program called SpeedTree, a proprietary 3rd party tool. It had some limitations because it's a procedural way of generating trees, using random parameters to determine the distribution of branches and how straight they are and where the leaves form. That's great for a random forest but in the case of the trees surrounding the White House, there are a number of iconic, recognizable trees. SpeedTree gave us a good starting point, and then we had to work very hard to match those trees as close as we could to the real ones.
The filmmakers were able to shoot some aerial photography from a distance, so there are times when the scene cuts between the actual White House grounds and our CG version, so we needed to be accurate. SpeedTree comes with a mechanism for simulating gentle breeze and, with a few iterations, we were able to get our entire library of White House grounds trees to move.
If a helicopter flies near the tree, however, the tree and its leaves need to be moving more violently from the downdraft. We used a different strategy for that. We found that the paint effects plug-in in Maya produces some very convincing tree/branch movement provided you don't see the trunk of the tree. In shots where you only saw the branches or tips of the tree, we used this paint effects approach. In shots with the whole tree, we developed a similar approach in Houdini similar to what we used in tree destruction, in which we used wire deformers, and the wind would cause the wires to flail back and forth.
As it worked out, we didn't have a silver bullet for trees, but we ended up with a Swiss army knife of solutions and we learned exactly which solutions to apply for each tree.
BLOWING UP THE CAPITOL DOME
We also blew up the Capitol Dome. This sequence had nowhere near the number of shots as the sequence with the Black Hawk helicopters, but the complexity of each of the shots was very high. This scene takes place much earlier in the movie; it's a diversionary tactic as the terrorists place a bomb in a cleaning cart in the middle of the Rotunda and it blows up.
The explosion expands out from the middle of the Capitol Dome, engulfs all the CG people and rises up, filling the entire cavity.
Three main shots tell the story of this explosion and we had a number of ancillary shots around it. One shot inside the Rotunda as the explosion goes off is a fully CG shot. We are looking down from the apex of the Dome as the explosion expands out from the middle, engulfs all the CG people and rises up, filling the entire cavity.
We cut immediately to an aerial shot, which was filmed from a helicopter. Our CG explosion blows out the windows and smoke billows out of each. The last shot in that group is a couple of hours later when all the fires have caused enough structural damage that the Dome completely collapses. These three main shots each had a team dedicated to them because each shot had quite unique needs.
For the interior shot, we initially thought the digi-double people would be a huge component of that shot, but as it ended up, the people were mostly engulfed in the explosion by the time we cut to it so digi-doubles were not as important as we thought. The shot became almost entirely about the explosion.
Shots of explosions are always tricky. When you do explosions, if you shoot them practically, you either expose down so you can see the details and everything is dark, or you let it blow out and see everything else. Directors always want the best of both worlds, so there's a bit of an exposure trick going on.
We hand-animated the CG people instead of using a rigid body simulation of them being thrown back by the shock wave. We created the Rotunda in full CG -- that is, everything except the statues. We realized it would be quite a lot of effort to model 12 statues all the way around the perimeter of that room. Not all of the statues are visible in the shot, and they're top down, so a CG version would be a huge undertaking for a small amount of screen time. Instead, we used a matte painting approach for that, under normal lighting and being lit from the explosion, and the compositor was able to apply the explosion light to those matte paintings.
The explosion itself was one of the hero shots for our in-house 3D pyro toolkit that we built initially for Abraham Lincoln: Vampire Hunter. We expanded upon it significantly to incorporate the new features of Houdini v. 12.5.
I've noticed a trend in the last three to four years in the prevalence of fully CG shots in movies like this. As the industry gets better at making photoreal objects, as we pay more attention to the shading properties and rendering and lighting of these scenes, it's going to happen more and more.
Obviously things like helicopter crashes and missiles will be done in CG because it's by far cheaper since you can redo them multiple times. If you blow up a practical helicopter once and don't like the shot, it becomes very expensive, very fast. Miniatures also had some artifacts that were a giveaway; the way the focus, light and small particulates would behave would key you into the fact it was a miniature.
In the last few years, the giveaway cues of CG have become so subtle and minute that practically no one uses miniatures. Perfectly straight lines and smooth edges are traditional classic giveaways of CG and, as CG practitioners over-compensate to fix that, sometimes you'll recognize CG because it's too imperfect. I think we'll continue to finesse back and forth in smaller and smaller increments. But the all-CG shot has clearly come into its own.
Images from White House Down are ©2013 Columbia Pictures Industries, Inc.