Realistic Movement with Motion Capture

In Making Pictures Move, we saw how classical animation techniques could be used to bring a series of fixed images to life, and as a result give an impression of animated movement.

We also saw how real movement could be captured using photography, as Eadweard Muybridge’s freeze frame photographs of a galloping horse demonstrated.

Making animated characters move in a realistic way is still a major challenge to animators today. Whilst many animators do still work in a traditional way – watching themselves in a mirror, for example, to see how to piece together a series of movements – it is now increasingly likely that big-budget productions will use motion capture (“mo-cap”) techniques to film the motion of actors performing a particular movement or series of movements, and then used this captured movements to bring alive a digital character, much like a puppeteer might bring alive a wooden puppet.

How so? Watch this movie clip showing how motion capture can be used put the human inside a digital puppet!

You may have noticed the unusual suit that the actor was wearing. The marks on the suit are high contrast areas that a computer can detect easily. By mapping different points on the filmed image of the suit with corresponding points on the digital avatar that we wish to animate, we can use filmed movements to drive the movements of the animated character.

Many motion capture techniques actually use pointwise markers on the motion capture suit. That is, individual markers are place at different points on the suit, often the joints. The motion of the person’s joints can then be matched to the joints of the digital avatar.

Another approach to motion capture is described in this research video on Practical Motion Capture in Everyday Surroundings (described in this paper in SIGGRPH 207).

Motion capture is widely used in films that make heavy use of CGI – computer generated imagery – as well as games. However, whereas Hollywood may use motion capture to create animated movement that is as realistic as possible, in games the actor may actually be required to perform ‘stylised’ actions that fit in with the genre of the game.

For example, here is an interview with one of the motion capture artists who worked on the Conan the Barbarian game: Age of Conan Site Tour Pt. 1 – Motion Capture.

If you watched the Conan movie clip, you may have picked up on the reference to motion capture being used with horses. The techniques used are certainly several steps on from anything Eadweard Muybridge attempted to do, as this brief post on the MTV Multiplayer blog suggests: A Horse Covered in Ping Pong Balls — The ‘Age of Conan’ Mo-Cap Shoot.


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