All images © Twentieth Century Fox. Supplied by Rising Sun Pictures.
CGSociety :: Production Focus
1 August 2013, by Paul Hellard
Rising Sun Pictures (RSP) created 266 VFX shots for The Wolverine, the new action film for Twentieth Century Fox. As part of the formative early sequences, Seventy-five RSP artists helped to recreate the World War II atomic bomb attack on Nagasaki in Japan. They also produced digital environments for a scene set in a snow-covered Japanese village, and combat effects such as digital copies of Wolverine’s iconic claws for use in numerous scenes involving challenging stunts. The work was conducted under the supervision of the production’s VFX Supervisor Philip Brennan, and VFX Producer Jamie Stevenson.
“RSP was one of the primary vendors on The Wolverine," says Stevenson. “Having worked with them in the past, we knew they would be a great fit for much of the claw work, but we also felt that they were the right vendor to take on several of the key sequences that required extensive environment work as well as challenging simulations and particle effects." RSP’s team was led by VFX Supervisor Tim Crosbie, whom was also VFX Supervisor on the second unit for the 'ice village' sequence.
“The view of Nagasaki, seen from across a harbour, required an extensive digital matte painting,” notes Crosbie. “We started by modeling the bomb after photographs of the actual blast but James Mangold wanted something unique and so pushed the blast into something never before seen. We were able to leverage research we had done for previous destruction effects to make an event that is much, much bigger and more immersive. It’s exciting stuff.”
Rising Sun Pictures worked meticulously to recreate the detonation and blast effects from the viewpoint of just across the bay from the Nagasaki explosion in August 1945. Tim Crosbie and spoke about the challenge. "There was a brief from Jim saying he wanted something a bit different. He said he knew the stock footage of the mushroom cloud that we all have seen. This was to show the initial blast, the flash, the dome of flame," he said. In Wolverine, the director also wanted there to be a deep interaction between a reconstruction of that event and the players in the movie. "Our goal was to generate something that the director responded well to, as well as being able to iterate it quickly," explains Crosbie. "The explosion almost became a character to escape from." Youtube: 'Trinity and Beyond'.
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RSP built a detailed 3D model of the prisoner of war camp based on a location outside Sydney, and then blew it apart as the radioactive shock waves rolled through. One of those waves carries Wolverine through the air. He lands in a stone well where he uses his body as a shield in saving the life of a Japanese soldier. “Components of the huts and wood that fly past the camera required a fair amount of choreography and numerous iterations to get the action beats just right,” recalls Crosbie. “Equally challenging was the pyroclastic cloud—the leading edge of the explosion—which sweeps across city and the water and through the camp ripping up buildings, guard towers and everything else in its path. Our team did a fantastic job.”
In the initial few seconds of the detonation, this is seen from across the bay from the relative safety of a WW2 prison camp. The highest viewpoint on the sequence is the grandstand view of the prison towers.
"When you run a simulation of an explosion, you can set all the starting conditions, but you can never tell exactly what you get at the end of it. Sometimes, you'll get a bit of serendipity and something you didn't expect, and you may be lucky and like it." Creating a presence that large, you need to load a vast amount of resolution to catch as much detail as possible. This will also take an enormous time to render out. "Clearly we couldn't get an off the shelf solution for the whole sequence, but we did use Houdini for the explosion and built a lot of tendrils upon it," explains Prema Paetsch, FX Lead at RSP. "We did have an off-the-shelf mushroom cloud simulation, and changed a lot of the framing and timing but we soon found that we couldn't just run a simulation for days." The RSP crew eventually ran a particle system which was driven by that initial mushroom cloud simulation and ran a set of smaller simulations which would be part of the pyroclastic motion around the base of the initial explosion. That way, they were able to create enough of the visuals, at the right resolution, volume, scale and detail. "This ended up being quite manageable and the simulation times could all be parallelised because they were independent, pyroclastic featurees that we could run and iterate on all at the same time," he adds. "Using some smart instancing, to distribute these, pre-cached, into the particle system of the master simulation."
Generating the extra, smaller impacts and explosions of the many buildings and superstructures on the ground at the base of the bomb was the next challenge. But also, the background matte painting of the Nagasaki environment and backdrop was another main challenge. Paetsch created a ring shaped particle system that would emminate out from the centre of the explosion. This would have that pyroclastic look, triggering explosions along the way. "We were to make sure to have the matte painting of the city, dated and true to the city's appearance at the time," said Crosbie. "In the closer shots, there was a very simple ground-plane, with a nod towards the architecture of the time. Since pyroclastic clouds do move extremely quickly, especially straight after an explosion of such scale, while it needed to show foreground superstructures, even if it was only for a few frames."
One of the signature shots of this sequence is of Logan (Hugh Jackman) surfing a pyroclastic wave into a well, shielding a Japanese soldier from the full flame force of the explosion at the bottom of the shaft. Overall VFX Supervisor Phil Brennan had a Japanese POW camp built down near Botany Bay, south of Sydney. This was where they shot a lot of the background plates for the sequence. "From this, we had a clean background, some practical elements and a green screen plate.," explains Crosbie. "We took the LiDAR scan, broke that down and rebuilt all the geometry that existed for the scene, to a level where we could then blow them up, using the Bullet physics system in Houdini." RSP started off using projected textures from the clean plates, which worked for the builds that were relatively far away, but they needed some of these pieces to fly towards camera. Several ignition points were employed to cheat more pieces of debris to fly towards camera instead of heading off to the sides. The shock wave's effect itself was created using fast fluid sims and some particle sims as well, running along the geometry based on that LiDAR. This was all based on the pyroclastic work that the team had done in the previous shots across the bay.
Rising Sun pulled together a vast amount of elements, compositing the shock wave effects together. "If the crew was careful placing these elements together, the sense of scale of complimented successfully," notes Crosbie. "We had the full team running on this, and everything was bedded in. The more stuff that's in there, as long as it is working the right way, you get that much higher level of details, and that's what sells the sense of scale."
"If you can see what we did, then we haven't finished yet."