Blending puppetry with 3D animation provides plenty of challenges for Prime Focus, as they give kids’ classic Tales of the Riverbank a 21st-century remake.

The partnership between UK and Indian post-production facilities formed when the Prime Focus group bought VTR in 2006 has come into play on its first major visual-effects project, Tales of the Riverbank.

Directed by Spitting Image’s John Henderson, Tales of the Riverbank is a feature film remake of the popular children’s TV series of the early 1960s.

The film tells the story of three friends – Hammy Hamster, Roderick Rat and GP the Guinea Pig – who, having been swept downriver in a violent storm, embark on an epic journey in search of their lost homes.

The animals’ adventures include encountering the evil Fat Cats and their WMD (Waffle, Marmalade and Doughnut) factory. While the original programme used real animals as the characters, the remake uses puppetry and 3D animation with the furry cast members voiced by stars of British comedy, including Stephen Fry and Steve Coogan.

As the film was shot almost totally against bluescreen, the vast majority of the visual-effects shots that Prime Focus created involved multiple rig and puppeteer removal, with keyed-out elements then tracked and composited into real riverbank backgrounds.

Nearly 1,200 shots of this nature were finished at Indian facilities in Mumbai, Chennai, Hyderabad and Parel, while the remaining, more complex, shots were completed in London.

This allowed the British client direct access to the work in progress. The shots handled in London ranged from extensive CG set builds and fluid simulations, including the entire WMD factory and its bubbling marmalade, to the film’s fully CG characters Owl, Falcon and Flea.

The project’s immense scale called for a streamlined pipeline and close coordination between modellers and animators. “The pipeline was developed around the tight delivery of shots,” explains John Harvey, head of 3D/VFX at Prime Focus London (PLF). For modelling, texturing and animation, the PFL team used Softimage|XSI.

“Without the exibility of XSI’s modelling and texture tools we would have struggled to deliver within the tight timeframe,” explains Harvey.

“The animation editor with its ability to mix IK with FK enabled the main CG character of the Owl to have quite a detailed library of moves. Also XSI’s customizable sliders and synoptic view allowed for quick editing and layouts. It has become our base package for animation due to its flexibility.”

Some supplementary atmospherics were created in Autodesk Maya, while the fluid simulations were achieved with XSI and RealFlow. “These required an extremely capable and technical operator to achieve the look and feel we needed,” notes Harvey.

Completing the pipeline were ZBrush for the fine detailing of the elements, Photoshop CS 3 for the digital matte paintings and Boujou for tracking. “We began by conceptualizing all the CG elements and creatures in the film, creating concept art for approval before any 3D work was started. The factory exterior and interior were also painted up, and their look and feel approved before build,” he says.

“We also completed several inline tests in order to establish techniques and limitations. Normally this would be done pre-production but due to time constraints we had to do most of this on the fly.”

The team’s main challenge in creating the CG characters was matching them to the look and feel of the puppets used in the film. The design for the Owl character, for example, went through several stages.

Based on the figure of an eagle owl, and drawing on the character of the actor (Stephen Fry) who voiced him, several designs were presented before the green light was given for the character’s appearance.

The first build of the Owl character in Softimage|XSI was anatomically perfect, built up from a skeleton with first muscle groups added then feathers. Initial animation, however, proved too realistic and didn’t gel with the more stylized puppets used in the film.

“We then decided to derive our skeletal structure for the Owl from the same system employed with the puppets in the film,” says Harvey.

“This presented a challenging task for the animators and modellers, as the Owl’s movements needed to look somewhat mechanical but realistic – as if they had inserted a pole into the character and sticks into the wings.“

Derived from a real owl, the feathers were dynamically animated using Softimage’s Hair system allowing for realistic bodily interaction. The Owl’s head movements and facial expressions were controlled using an elaborate ray of sliders.

The wings had several expression operators linked to the bones, which in turn controlled how the feathers behaved, allowing the wings to be folded without feathers cutting through each other.

Secondary expressions were used to control the wind ruffle. The biggest CG set challenge facing the PFL team was the interior of the WMD factory. The entire interior set was built in CG to allow for the complex lighting, fluid simulations and particle generations. The marmalade that features in these shots was created using two different techniques.

“The original brief was to create a liquid that shared properties with marmalade and boiling lava, to increase the sense of danger facing the hero characters,” says Harvey.

“The boiling marmalade was a flat, semi-transparent surface with an in-house developed animated bubble shader driving the displacement of the surface,” he explains.

“This was broken down into multiple layers (growing bubbles, popped bubble residue, and residual ripple noise), which gave the surface lots of interest in the diffuse reflections and refractions.

We also added marmalade shred below the surface and animated this to give the marmalade more depth and life.” To create the flowing marmalade, the team turned to NextLimit’s RealFlow fluid simulation software. The team began by conducting several animation tests in order to get the correct level of viscosity and the scale for the liquid marmalade.

“Lots of the settings can be bracketed – in the same way exposure can be bracketed on a camera – to make slight changes in the variables available to us such as viscosity, density, surface tension, and internal and external pressures. We can then see the result and alter the settings appropriately,” explains Harvey.

The locations that featured the CG marmalade were also modelled to match the footage, allowing the gooey liquid to fit and interact with the filmed sets and characters.

According to Harvey, the hardest shot to create was the smashing cauldron of liquid marmalade because it involved a rigid-body simulation to mimic the impact of the cauldron on the floor.

Using RealFlow, the rigid-body simulation was completed as a first pass before the fluids, with the animators using RealFlow’s stacking RB solver to correctly calculate the chain of forces needed to hold the fragments of cauldron together as it falls under gravity towards the ground.

“A similar simulation in other packages often causes the pieces to ‘explode’ apart at the first frame, requiring workarounds,” explains Harvey.

“With a successful and approved cauldron simulation, I was able to fill the cauldron with the thick marmalade-like fluid. The floor was given a high friction value to get the marmalade to slow down or stick when it collides.”

Prime Focus London created additional – mainly supplementary – CG elements for the film. These ranged from balloons, flying rocks, slime drops that fall from the sky like rain, to a waterwheel on the side of the WMD factory.

CG set extensions were also called for, including a decimated landscape and tar pits, and the main river itself. “These were particularly interesting shots as they were combined and supplemented in Eyeon Fusion, which uses normal maps in an Open EXR format. This enabled fast updates and tweaking, with the final look being achieved through a seamless pipeline from CG to Fusion,” says Harvey.

Following on from the CG and compositing, a digital intermediate (DI) process was completed entirely in London which, because of the heavy VFX nature of the film, took three months to finish. The film has yet to be given a release date but expect it at cinemas soon.

“The Owl is a great piece of CG character animation,” says Derek Moore, head of 2D at Prime Focus London. Initially a very detailed skeleton structure was built, but initial animation test proved too lifelike, which sat awkwardly with the puppets used for the other characters, says John Harvey, head of 3D.

“So we decided to derive a skeletal structure from the same system employed with the puppets.”

When it came to producing the final render for the Owl shots, the 3D team started with ten layer passes before narrowing these down to five for a typical build. Several render passes were predefined and combined, to reduce the workload for the compositors while letting the dual quad-core renderfarm take the strain.

The interior of WMD factory was the biggest set challenge, says John Harvey, as it included cauldrons casting their own lights on the interior walls. While models were built for the external shots of the factory, the interior set was recreated in CG to allow for the complex lighting and particle generations.


Project: Tales of the Riverbank
Client: Riverbank the Movie
Studio: Prime Focus London
Software: Softimage|XSI, Adobe Photoshop CS3, NextLimit RealFlow, Pixologic Zbrush, Eyeon Fusion, Autodesk Maya