Kubo and the Two Strings: the Moon Beast

The climax of Kubo and the Two Strings involves the battle between Kubo and the Moon Beast, a giant flying glowing monster. It’s the first puppet that LAIKA has done that was completely created using their 3D printing-based rapid prototyping technology.

The decision to approach the puppet that way “started with the storyboards sitting in a room together,” says VFX Supervisor Steve Emerson. “Brian McLean, who’s the head of rapid prototyping says, ‘I think I can print this whole thing up.’ That confidence is coming from the fact that during Kubo we moved from powder-based printing into plastic printing.”

In the final battle, the Moonbeast chases Kubo through the town square, wreaking destruction on the buildings. In order to achieve the final composite, a combination of practical and digital elements were created. In the clip below, Steve Emerson discusses the work which went into creating the final result.

The plastic printing provided several advantages. First, it wouldn’t break as they moved the characters frame by frame because the material is much more rigid than what was used in the past. The plastic-based printing also allowed them to use translucence, which was important for the character design.

The team went through several rounds of look development to establish a color palette that referenced grandfather’s final design while honoring the concept art.

The Moon Beast surface had intricate scale-like texturing as well as lines that appeared to glow and radiate light. The team would treat different parts of the puppet with invisible UV paint and then would capture it lit with a black light. “Whether the particular paint was red or green or blue,” says Emerson, “we could isolate specific areas to be able to create mattes in those color channels.”

For each frame/pose of the puppet they would capture several passes:

  1. Lit with an overall white flat light
  2. Lit with a shaping light to provide dimension
  3. Lit with black light to expose the UV paint
  4. Silhouette green screen pass
The three exposures that mimicked a CG lighting workflow: a flat diffuse white light, a more specular shaping white light and a UV pass for matting certain areas.

The translucent plastic was also important to allow the Moon Beast to glow and shimmer from within, with the effect achieved in a surprisingly practical way by members of the team. “They go down to Fred Meyer [a local store] and they buy like 100 of these gold Mylar balloons,” says Emerson. “They bring them back to LAIKA and they start cutting them up and scrunching them up and shoving them into the puppet in order to get a very specific lighting coming off of those surfaces. It’s all just crazy,” he jokes.

The main color process was done in 2 layers and used a combination of the 2 white light passes. The flat light provided a nice base layer to push warmer tones of purple and gold into the shadows and midtones. The shaping light gave greater contrast on the scales and illuminated the gold foil underlayer. We used this to selectively add green and blue tones in the midtones and highlights and to add targeted areas of gold shimmer.

The final touches were done using mattes extracted from the ultraviolet light pass. Glowing cyan accent lines were added on the head, body & fins. Mattes for the eyes and battle wounds were extracted to add a sense that he was illuminated from within by his inner moonlight.