Intelligent linear rig tightens up film production
11 February 2011
Production of stop/motion animated films at Ko Lik’s Edinburgh film studio is proceeding more smoothly, in part thanks to some rather clever design work based on a linear actuation system
Funded by BBC Scotland, the ‘Glendogie Bogey’ stop/motion animated film was the sequel to the BAFTA-nominated ‘Haunted Hogmanay’ and the brain child of Ko Lik Films, an Edinburgh based company specialising in stop frame animation. This painstaking process involves clay models being moved, frame by frame, to create a sequence. It is particularly time consuming work as typically 25 camera shots are required to complete a sequence that is just one second long.
Historically, Ko Lik mounted the camera on a hand wound helical screw that allowed it to be moved along the scene set. However, this was neither accurate nor flexible, and resulted in increased production hours and compromised cost-efficiency. The company decided to seek the help of engineering designer and model maker, David Campbell and his colleague Michael Gormley, who takes up the story:
“We explored proprietary motion systems for Ko Lik but they were too costly and over-specified for its needs, 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 system devised by the Campbell/Gormley team comprises two HepcoMotion PDU profile driven units with a SmartDrive stepper motor and controller. Designed to straddle the set, it was a fairly long-winded development, as Mr Gormley explains: “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.”
The rigidity of the profile driven units was deemed important. As the system is cantilevered, the vertical axis had to provide solid support for the motorised X-axis on which the camera is mounted. The designers also had to contend with an element of bounce within the system, but the rigidity of the beams and the 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 the rig, however, is its controllability. The camera is able to move a set distance to within a tolerance of 0.1mm and, most importantly, provide a datum, which 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 SmartDrive 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. With the new system, these algorithms are fed into the controller so it has executable routines that the camera operators can simply run – and it is completely transparent to them. Michael Gormely concludes:
“In the greater scheme of things, this was a fairly small job but both HepcoMotion and SmartDrive, were only too pleased to give us the benefit of their knowledge.”
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