tailieunhanh - Book: Computer Animation

Optical motion capture systems are based on small reflective sensors called markers attached to an actor's body and on several cameras focused on performance space. By tracking positions of markers, one can get locations for corresponding key points in the animated model, . we attach markers at joints of a person and record the position of markers from several different directions. We then reconstruct the 3D position of each key point at each time. The main advantage of this method is freedom of movement; it does not require any cabling | Computer Animation Nadia Magnenat Thalmann MIRALab University of Geneva Geneva Switzerland E-mail thalmann@ Daniel Thalmann Computer Graphics Lab Swiss Federal Institute of Technology EPFL Lausanne Switzerland E-mail thalmann@ Introduction The main goal of computer animation is to synthesize the desired motion effect which is a mixing of natural phenomena perception and imagination. The animator designs the object s dynamic behavior with his mental representation of causality. He she imagines how it moves gets out of shape or reacts when it is pushed pressed pulled or twisted. So the animation system has to provide the user with motion control tools able to translate his her wishes from his her own language. Computer animation methods may also help to understand physical laws by adding motion control to data in order to show their evolution over time. Visualization has become an important way of validating new models created by scientists. When the model evolves over time computer simulation is generally used to obtain the evolution of time and computer animation is a natural way of visualizing the results obtained from the simulation. To produce a computer animation sequence the animator has two principal techniques available. The first is to use a model that creates the desired effect. A good example is the growth of a green plant. The second is used when no model is available. In this case the animator produces by hand the real world motion to be simulated. Until recently most computer-generated films have been produced using the second approach traditional computer animation techniques like keyframe animation spline interpolation etc. Then animation languages scripted systems and director-oriented systems were developed. In the next generation of animation systems motion control tends to be performed automatically using . and robotics techniques. In particular motion is planned at a task level and computed using physical laws. More