From the opening minutes of Kubo and the Two Strings, directed by Travis Knight, it's clear that team at LAIKA broke new ground for the company with the vast amount of water effects in the film. That's not to say there hasn't been any water on screen in their previous films, but it was treated as a practical effect and not CGI.
A previous example would be in their 2009 film Coraline. In one scene, Coraline wanders into a bathroom, turns the shower on, and she's sprayed with this rusty, rancid water. That was all achieved using replacement animation, which was achieved via replacement animation where streams of water are swapped in one frame at a time. Rapid prototype (RP) 3D printers were used to create each physical frame of the water animation.
For their next film, Paranorman (2012), there is a scene where Norman is in the bathroom at school and his uncle makes his first appearance as a ghost. A quake occurs and water spills out of the toilet and under the floor. The team at LAIKA used a lot of 3D printing with replacement animation, but also used different types of gelatins that could actually be formed and moved one frame at a time.
"The thing about Kubo is that it's epic and it's huge," says LAIKA VFX Supervisor Steve Emerson. "The first thing that I was shown when we started talking about the fact that we were going to make this film was the opening sequence. We certainly weren't going be able to buy enough of whatever that gelatin was that the animators use -- KY Jelly or whatever the heck it was going to be. We knew it was going to end up being some type of a computer generated solution."
Even though it was going to be a computer generated solution, it was critical that the style and look fit in with the traditional stop motion animation LAIKA is known for. "That's a really, really important thing that we learned early on when the scope of these films started to just grow," says Emerson. "How do we do that in a way that we can create visuals that feel that they belong in the stop motion hand-crafted environment? The answer to that was largely through collaboration."
They started by examining the visuals created by the art department and figuring out how to bring a painted image to life. The look of the film is very much a love song to Japanese wood block art, and in particular that of Kiyoshi Saito. "You end up with a lot of plain or negative spaces that are offset by areas of very, very dense information," says Emerson. There is "a very, very soft color palette which is offset by colors that are very, very bright and brilliant. Because of the wood block process itself, which is created by a carving of wood with papers pressed up against it, you get this really, really cool texture almost like a wood grain."
They turned to LAIKA Animation Rigging Supervisor Oliver Jones and the rigging team for physical references for the types of looks they needed to create. Emerson explains the process in the video, below.
With the physical references and collaboration with the practical team in high gear, it was time to tackle the problem of creating digital photo-realistic water and making it feel like it belongs in Kubo's stop motion environment. While the shuttering of Rhythm and Hues after the release of Life of Pi was truly unfortunate, it did provide an opportunity for Kubo. Emerson immediately contacted David Horsley, who was water effects lead on Life of Pi, and brought him up to Portland to let him know about the project. "I think David was very much excited about the fact that he was going to have the ability to make a real impact on this film," says Emerson. "He was going to be driving a lot of the visuals, because a lot of this film takes place on water."
The biggest challenge was to stylize the look so that the water fits with the rest of the show for style, which means essentially animating Japanese woodblocks." Adding wood grain on water was fun," says Horsley, "so we used wood grain textures but we also used procedural noise and fractals that complemented the wood grain and helped integrate it."
One concern the team had early on was scale. They needed to establish what the correct scale would be to make sure the physics were going to respond correctly to the puppets, as if Kubo and the other puppets were at normal human scale. AT LAIKA the puppets are tiny in reality, so scale was a big focus at the start of the project. Matching the water to the animation wasn't an issue according to Horsley. "The stop motion at LAIKA is so smooth that really all we needed was an accurate object track for the puppets and to simulate water around the characters as one would normally," he says.
Due to the vast amount of data that simulations generate, as well as the various render elements, the water put added stress on LAIKA's infrastructure. Horsley jokes that he's "always been at the top of the list of the worst offenders for disk space usage." LAIKA did invest in more disk space, but for render capacity they needed to work smarter and more efficiently to make sure the render farm wasn't saturated.
Horsley relates that "every night the leads would meet and discuss what goes into the farm, what gets rendered on 10's, which elements should be 1k or 2k (fog for example is fine at 1k), which elements can slow cook on the back burner, and which elements we can backup and remove, etc."
The main effects software used on Kubo was SideFX's Houdini. At Rhythm and Hues for Life of Pi, Horsley feels that the Houdini team made great strides on their water simulation software, and during Kubo they kept improving the software to be able to do more complicated work. "I was most impressed with a sim of a beach scene with the foam lapping up on the shore," says Horsley, "the sim looked great as a first take out of the box."
The VFX team at LAIKA is about 60 artists out of the approximate 400 people who make up the crew for the film. This is quite small considering the amount of work that needs to be accomplished. The 3D team rendered deep camera maps, allowing the compositors to work at least partially in 3D. For Horsley, the key to integration was largely about motion. "If the physics of the water simulation worked realistically with the animation then that immediately sells the fact that the puppet and the water live in the same world," he relates. "But as long as I provided the compositors options for elements, they were able to pick and chose which elements work best for them."
For Kubo, LAIKA had not worked on really large scale effects scenes that involved dozens (or hundreds even.) of elements. Getting water working right involves all elements working together as part of a symphony, says Horsley. If one element is off or changes then it effects all the other elements and one needs to adjust several other components to ensure things work well together again as a unit. "The biggest challenge was to get Travis to sign off on some pretty rough looking base simulations, that would provide the foundation for all the other water elements in a shot," says Horsley. "The solution was not a technical one, Travis just trusted us, so with some soft selling we moved the shots along."
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