OSLO, NORWAY — Storm Studios (www.stormstudios.no), here, recently created troll characters for the film The Trollhunter, which is being distributed in the US and Europe. The film marks the feature debut of director André Øvredal, and was produced by John M. Jacobsen and Sveinung Golimo from Filmkameratene AS.
The concept of the film centers around the Norwegian government hiding a secret population of trolls, which are living on game preserves, safe from the public eye. High tension power lines actually form an electric fence that keep the beasts contained. The studio used Maya to set up the base meshes for sculpting in ZBrush. After texturing was done, artists continued sculpting with projected desaturated textures which allowed them to add more details to the sculpt as well as aligning it up with the textures.
“By using ZBrush, we were able to model with a very high polygon count without worrying about it,” notes VFX production manager Vicky Kwan. “For retopology of our creatures we used Topogun, and all parts of the troll was assembled in Maya with displacement maps extracted from ZBrush for render. UV mapping was done in Headus UV Layout, which made sure we saved a lot of time on that process.”
Storm Studios relies heavily on Houdini for their VFX work. The animation software helped in setting up procedural systems
that could be run through whenever there was a new change on a shot. L-system was used to create trees that the trolls could interact with. This, combined with a setup of Houdini's particle system that emitted falling debris when trolls pushes the trees around, created the level of detail and flexibility needed to integrate the CG into the plate. The L-system was later used as a base for Maya’s PaintFX that was rendered out with the studio’s existing Renderman pipeline.
“We also used Houdini's SOP architecture to create the base for an effect where the troll turns into stone when it gets hit by a strong light,” adds Kwan. “Again, the procedural nature of Houdini made it possible for us to get a fast previz of the effect and update it whenever the animation of the shot changed.”
Shave and Haircut was used to groom the trolls, in combination with paintFX. “We used the simulated curves generated from Shave and Haircut to control the movement of the PaintFX, although at the end this was deemed unnecessary on most of the shots and the dynamics were controlled separately,” says Kwan. “We had to write our own scripts for being able to simulate the fur and PaintFX distributed on our farm. This was essential since we had several trolls with approximately one- to two-million hair strands each in shots that spanned 500-plus frames.”
Renderman was used for exporting hair and PaintFX as rib files. Trollhunter was rendered using Renderman Studios. The complexity of the trolls required new custom shaders be created, so the studio developed a new general shader that was able to handle all aspects of the setup. Nuke was used extensively for compositing. The camera tracker in the app proved to be an efficient and valuable tool for tracking hand-held shots.
“Much of the film was shot with night vision,” explains Kwan, “and matching the color artifacts, warping and noise produced by the night vision function of the camera became an important part of integrating the digital trolls into the rather rough plates. Nuke's flexibility proved very valuable in providing a solution for getting the trolls integrated and make them a natural part of the plate.”