Green screen techniques allow parts of an image to be replaced, which allows a small number of actors to portray large scenes, like the D-Day landings. Motion capture involves tracking markers placed on actors' bodies to capture their movements and apply them to digital characters. Markerless motion capture systems aim to capture more subtle movements without markers by tracking the body. Both techniques are used widely in movies and games to bring realistic digital characters and environments to life.

1. Where Digital Worlds Meet the Real World: From Chroma Key to Motion Capture

2. 1. Do you believe whatever you see in the movies? Here's how to portray the D-Day landings with 3 people and a green screen...

3. So how did that work? Green screen/chroma key techniques allow part of the image to be masked out and then replaced with a different image playing within that mask

4. (and what's so special about GREEN anyway...?)

5. Motion Capture (or mo cap) is the process of capturing human or animal movements in such a way that they can be used to animate “digital actors”

6. By placing markers on and close to skeletal joints, it is possible to capture which bits of the skeleton move – and how – whenever a particular action is performed

7. ...and it's not just for capturing human movements...

8. So how does motion capture work for games?

9. Having to use markers to capture the movements adds a significant overhead to the process of motion capture, (it can be a fiddly job locating the markers).

10. Using markers also limits what data is actually captured... ...so ideally, we'd like a markerless system

11. Why? Because markerless motion capture can be used to capture tiny facial movements, as well as full body movements

12. http://digitalworlds.wordpress.com