Intelligent linear rig

for a film production

HepcoMotion

Thanks to some clever design work based on a linear actuation system, production of a stop/motion animated film the Glendogie Bogey was a slick operation.

Funded by BBC Scotland, the stop/motion animated film ‘Glendogie Bogey’ was the sequel to the BAFTA-nominated ‘Haunted Hogmanay’ and sees two friends go in search of the fearsome monster, the Glendogie Bogey, that lurks in caves under a golf course.

The film was the brain child of the Edinburgh based, Ko Lik Films. The company specialises in stop frame animation, a method that involves clay models being moved, frame by frame, to create a sequence. This is time consuming work as typically 25 camera shots are required to complete one second of film.

Historically Ko Lik used a rig whereby the camera was mounted on a hand wound helical screw allowing it to be moved along the scene set. However, it was neither accurate nor flexible. This resulted in increased production hours and compromised cost-efficiency. The company therefore sought the help of engineering designer and model maker, David Campbell and his colleague Michael Gormley.

“We explored proprietary motion systems for Ko Lik but they were too costly and over-specified for its needs,” explained Michael Gormley. “So we set about designing a system ourselves. And although what we came up with was a fairly straight forward two-axis system carrying a small load, there were several factors that made it a nifty bit of kit.”

The resultant system comprises two PDU profile driven units with a stepper motor and controller. Designed to straddle the set it was a fairly long-winded development. “We had to translate exacting production needs into design engineering and both HepcoMotion and its motion control partner SmartDrive contributed a great deal in this regard,” Michael continued.

The rigidity of the profile driven units was an important criteria. As the system is cantilevered, the vertical axis had to provide solid support for the motorised X-axis onto which the camera is mounted. Michael and David also had to contend with an element of bounce within the system but the rigidity of the beams and use of the motor to counterbalance the camera and camera head at extremes of travel ensures that this effect does not compromise the camera’s positioning accuracy.

Key to the success of this rig is its controllability. It is able to move the camera a set distance to within 0.1mm accuracy and most importantly provide a datum. This is critical from a production cost standpoint. When a sequence has been shot it is naturally reviewed for quality. If part of it needs to be re-taken, it is now easy for the production team to re-shoot, for example from frame 10-20 in a 100-frame sequence. This is because the exact camera position is now known.

The controller also provides other highly valuable automation features. Knowing what distances to move the camera to achieve the required visual effect is a complex task. Historically it needed a combination of mathematical calculation and intelligent guesswork on the part of the production team. “On the new system we have fed these algorithms into the controller so it has executable routines that the camera operators can just run,” Michael explained. “It’s completely transparent to them.”

In conclusion Michael Gormley praises both HepcoMotion and SmartDrive for their ongoing advice on this project. He said, “In the greater scheme of things this was a fairly small job but both companies were only too pleased to give us the benefit of their knowledge.”

Edited by Constanze Schmitz