|
Anyone who has seen recent blockbusters like The Lord of the Rings trilogy or King Kong will understand the power and impact of dazzling special effects. And they just seem to get better and better.
This is down to the development of increasingly clever and sophisticated computer technologies. Even ten years ago, using computer animation was time-consuming, laborious and expensive, but now accurate and life-like animations can be produced in real time at a fraction of the cost.
Having been developed out of pure research carried out by robotics experts, two key technologies, Motion Capture and Motion Tracking, are revolutionizing the film business.
Computers and the Art of Film Animation
Motion capture
Motion Capture is used widely in film and TV special effects, firstly because it speeds up the animation process, and secondly its accuracy in capturing movements leads to a much more realistic animation than could be achieved with simple hand animation. It was Motion Capture that transformed Andy Serkis into the ‘creature’ Gollum in The Lord of the Rings films.
Motion Capture works by recording the subtle and complex movements of a subject in 3D, and the results are then used to "drive" a computer generated character or object. As long as you can attach a marker to it, you can capture the motion of just about anything - someone dancing or fighting, a ponytail, a sword, a football, even a curtain. Specialist high resolution cameras record the movements at up to 1,000 frames per second (compared with 25 frames per second in normal TV video) and up to 24 cameras can be used simultaneously. Each is carefully positioned so the performer can be seen through 360 degrees. The cameras capture the reflection from the markers and these images are fed into a processor and converted into 3D data, which shows up as dots on the computer screen.
Highly refined software then reads the dots to understand how they relate to one another and to work out how to join them together in a 3D space. For example, if you are animating a gymnast, it's important the software understands dot A is a wrist and should be joined to dot B on the elbow - so when dot T on the foot crosses dot A, the animated gymnast does a somersault and doesn't turn itself inside out. The process is complicated - even more so if you're recording several different performers at the same time - but once the image is made, you can play around with it as much as you like. Applying an actor’s physical performance into a 50 foot gorilla, say.
But it's not just films, pop videos and electronic games that use Motion Capture. It's also invaluable in science research labs, specialised hospital clinics, and sports facilities. Ergonomics labs use Motion Capture when they examine how a subject interacts with its environment. By recording the precise way people move and act, car manufacturers can design car interiors much more effectively. The high degree of precision data produced by Motion Capture lets hospital surgeons plan operations in greater detail beforehand. And sports trainers and physiotherapists use the technology to devise individual training and treatment plans. At Strathclyde University, Motion Capture is used to analyse how different ships' hulls behave in wave tanks.
Motion tracking
Motion Tracking is a slightly different technology which combines real film footage with computer animation. 3D positional information is extracted from existing film and this is then analysed by software to create an exact replica of the scene, including trees, buildings, cars etc. Motion and camera data such as angles and lens characteristics, are preserved and the combination of these means you get a much more convincing match between computer graphics and live film or video. Although it is used mainly by filmmakers, people outside the special effects industry, such as architects and industrial designers, are starting to benefit too.
Motion Tracking is based on machine vision research carried out by robotics experts, which allows robots to interpret what they "see". Footage is scanned by software for "features" - points where a pattern of pixels is consistent from frame to frame. (Pixels are miniscule areas of the screen and can be anything from the tip of a blade of grass, to the corner of a picture frame, or the tiny shadow cast by a few grains of sand). These are tracked from frame to frame; the results are analysed statistically and consistent movement (such as wind in the trees) is picked out.
The computer rejects anything which isn't scenery, unless the user forces it to track a moving object, such as a plane. The software also works out things like camera movement, aperture and focal length which helps ensure the animation being inserted into the scene doesn't look out of place.
Motion Capture and Motion Tracking are most often used in the entertainment business but they rely heavily on the hard science carried in robotics, machine vision and artificial intelligence. The hardware - such as the cameras which capture spatial information - is produced by specialist engineers, who work closely with animators to understand their requirements and how the system will be used. Working together, the artists and the scientists are making sure that from now on, we just won’t be able to believe our eyes.
|
