Horror mocumentary: The Troll Hunter

3D World | Features | Making of | 18/01/2012 14:43pm

Rune Spaans of Superrune and Lars Erik Hansen of Gimpville reveal how they helped bring Norwegian folklore to life in André Øvredal’s monster hit, The Troll Hunter

For a film so thoroughly Norwegian – suffused with dark, Scandinavian humour and drawing heavily on local folklore – The Troll Hunter has proven a surprisingly successful export. So much so that Hollywood has grabbed the rights for an English-language remake.

Along with some work completed in-house by production company Filmkameratene, Storm Studios, Gimpville and one-man-band Superrune were the principal effects studios involved with the project. The latter’s Rune Spaans also handled the modelling for the base troll design, with a look inspired by the work of 19th century Norwegian artists Theodor Kittelsen and Erik Werenskiold, and contemporary illustrator Svein Solem.

Spaans admits that he hadn’t originally intended getting involved with another movie project: “I’ve been trying to get out of visual effects for some time, but when they emailed a rough script and some concept designs I just knew I had to do it. I found a sequence that I felt I could manage on my own, and also put in a bid on finishing off the character design for the film. Looking back, it’s amazing that they took the chance on a one-man company.”

“I built a stunt sheep to find the optimal pipeline for the troll, so he went through several hair tools and a lot of script testing,” says Spaans. “My animator also made a madly detailed double for the actor.

Superrune’s sequence in the movie depicts a violent showdown between a heavily armoured troll hunter and a troll living under a bridge. Initially working alone, though eventually bringing in animator Atle Blakseth to help out, Spaans realised he would need to work cleverly to keep everything manageable.

“I figured a detail level that matched videogames or TV animation would be a good starting point, making sure I could scale up from that if there was time,” he explains. “I wrote a lot of scripts to make the pipeline as non-linear as possible. I initially thought an asset tracking system would be overkill, but did end up programming a very simple one halfway through the project, just so I could rebuild the shots with improved rigs and shaders.”

Pushing towards real-time performance, Spaans says his troll model was incredibly simple, with just 3,400 polys at the base level (and around 2,000 of those were for the teeth). “All the details are in the displacement map, added after the model has been subdivided to seven million polys at render time. The rig, based on one I’ve been scripting on and off for the past four years, also adhered to a ‘keep it simple’ philosophy. There were probably no more than a hundred animation controls, which increased viewport performance and kept the whole process as fast as possible.”

The troll’s fur was added in Houdini and SynthEyes was used for tracking, with all shots composited in Nuke

Muscles were a last-minute addition to his rig. “They were built and skinned using SkinFX, and simulated using the built-in ‘flex’ soft-body dynamics in 3ds Max, which was very unstable,” says Spaans. “I managed to get it under control with constant keyframing, but it was a risky thing to do on deadline.”

A regular collaborator with Filmkameratene, Gimpville created the giant troll that stomps across Norway’s snowy wastes near the end of the movie. “We knew from the start that the ‘Jotne’ was going to be a huge undertaking, and luckily convinced Filmkameraten’s VFX producer Marcus Brodersen to spend almost 40 per cent of the budget on the character asset alone,” says Gimpville visual effects supervisor Lars Erik Hansen.

“This approach ensured that we would have an asset that would work in almost any shot, although I have to admit I was still a bit concerned when the director told us about the scene where the truck drives right between the troll’s legs!” As with the rest of the film, this sequence was shot in hand-held ‘mockumentary’ style, with rapid changes of shooting location making proper location surveying impossible.

For interaction between troll and landscape, Gimpville extended standard Houdini tools with a dynamic footprint system to solve snow quantity and movement speed depending on the impact of each footfall. A noisy particle system was used to add snow, filling in the space between the camera and the troll. “Due to the scene scale in some shots, we ended up with several million snowflakes dancing in front of the camera,” notes Hansen.

“We used Serg’s AxisSSS shader for the subsurfacing on the skin, adding layers of dirt and specularity for about 15 different passes,” says Hansen. “These were then rendered into multi-channel EXR files”

A dream come true

While Spaans knew the original script had potential, he says he never expected The Troll Hunter to be such a critical and commercial success. “I’m not really sure what it will eventually mean for the VFX community in Norway. And to be honest, while the work is pretty impressive considering the small teams involved, it’s nothing compared to the effects bonanzas moviegoers are spoiled with today. I’m very proud to have worked on it, though. It really was a dream come true.”

“Trolls, Vikings and folktales are an important part of our cultural heritage, so one of the coolest things about participating on this project was the opportunity to update people’s perceptions of what a Norwegian troll really looks like,” adds Hansen, who’s surprisingly optimistic about the upcoming Chris Columbus reboot. “We really are looking forward to the Hollywood remake… in fact it would be awesome if we got the chance even to do just a tiny bit of the VFX work for it!”

Troll Hunter image of troll showing lighting

KEY TECHNOLOGY

The starting point for Gimpville’s giant troll was Rune Spaans’ base model. Maya was used for modelling and retopologising, with HD sculpting performed in ZBrush. “The animation was done at Filmkameratene in Maya, using motion capture via NaturalPoint’s OptiTrack,” says Gimpville’s Lars Erik Hansen. “Everything came together in Houdini where we added fur and vegetation. SynthEyes was used for tracking, with shots comped in Nuke.”

The starting point for Gimpville’s giant troll was Rune Spaans’ base model. Maya was used for modelling and retopologising, with HD sculpting performed in ZBrush.

“The deformation rig was done mostly with Maya Muscle. The Jotne was first skinned to joints with standard skin weights. The muscle deformer was added to this skin cluster as a relative deformer, and the muscles bound using ‘sticky’ weights. Smooth maps were used for compressed and expanded areas on the mesh, with relax wrinkle and direction maps for bulging and wrinkling the skin and sliding maps simulating joints under the surface.

“Some vegetation was partly modelled in Maya with traditional techniques and some was created using paint effects. The vegetation had to portray a vast amount of detail. We solved this by scattering 40,000 points on the Jotne’s back and solving simple two-point lines on top of these. As it was mostly seen at a distance, we just needed to provide a general notion of mass and movement.”