Task 1 : Technology Research

Hi,
For my task 1, i have chosen motion capture technology to highlight its aspects,weaknesses and how this technology may be advanced within the short to medium term.
 

Motion capture

Motion capture, motion tracking, or mocap are terms used to describe the process of recording movement and translating that movement on to a digital model. It is used in military, entertainment, sports, and medical applications, and for validation of computer vision and robotics. In filmmaking it refers to recording actions of human actors, and using that information to animate digital character models in 2D or 3D computer animation. When it includes face and fingers or captures subtle expressions, it is often referred to as performance capture.
Camera movements can also be motion captured so that a virtual camera in the scene will pan, tilt, or dolly around the stage driven by a camera operator while the actor is performing, and the motion capture system can capture the camera and props as well as the actor's performance. This allows the computer-generated characters, images and sets to have the same perspective as the video images from the camera. A computer processes the data and displays the movements of the actor, providing the desired camera positions in terms of objects in the set. Retroactively obtaining camera movement data from the captured footage is known as match moving or camera tracking.

Advantages

Motion capture offers several advantages over traditional computer animation of a 3D model:

• More rapid, even real time results can be obtained. In entertainment applications this can reduce the costs of keyframe-based animation. For example: Hand Over

• The amount of work does not vary with the complexity or length of the performance to the same degree as when using traditional techniques. This allows many tests to be done with different styles or deliveries.

• Complex movement and realistic physical interactions such as secondary motions, weight and exchange of forces can be easily recreated in a physically accurate manner.

• The amount of animation data that can be produced within a given time is extremely large when compared to traditional animation techniques. This contributes to both cost effectiveness and meeting production deadlines.

• Potential for free software and third party solutions reducing its costs.

Disadvantages

• Specific hardware and special programs are required to obtain and process the data.

• The cost of the software, equipment and personnel required can potentially be prohibitive for small productions.

• The capture system may have specific requirements for the space it is operated in, depending on camera field of view or magnetic distortion.

• When problems occur it is easier to reshoot the scene rather than trying to manipulate the data. Only a few systems allow real time viewing of the data to decide if the take needs to be redone.

• The initial results are limited to what can be performed within the capture volume without extra editing of the data.

• Movement that does not follow the laws of physics generally cannot be captured.

• Traditional animation techniques, such as added emphasis on anticipation and follow through, secondary motion or manipulating the shape of the character, as with squash and stretch animation techniques, must be added later.

• If the computer model has different proportions from the capture subject, artifacts may occur. For example, if a cartoon character has large, over-sized hands, these may intersect the character's body if the human performer is not careful with their physical motion.

Facial motion capture

Facial Motion Capture or Performance Capture is the process of electronically converting the movements of a person's face into a digital database using cameras or laser scanners. This database may then be used to produce CG (computer graphics) computer animation for movies, games, or real-time avatars. Because the motion of CG characters is derived from the movements of real people, it results in more realistic and nuanced computer character animation than if the animation was created manually.

A facial motion capture database describes the coordinates or relative positions of reference points on the actor's face. The capture may be in two dimensions, in which case the capture process is sometimes called "expression tracking", or in three dimensions. Two dimensional capture can be achieved using a single camera and low cost capture software such as Zign Creations' Zign Track. This produces less sophisticated tracking, and is unable to fully capture three dimensional motions such as head rotation. Three dimensional capture is accomplished using multi-camera rigs or laser marker system. Such systems are typically far more expensive, complicated, and time-consuming to use.

Facial Motion Capture is related to body motion capture, but is more challenging due to the higher resolution requirements to detect and track subtle expressions possible from small movements of the eyes and lips. These movements are often less than a few millimeters, requiring even greater resolution and fidelity and different filtering techniques than usually used in full body capture. The additional constraints of the face also allow more opportunities for using models and rules.

Marker-based

Traditional marker based systems apply up to 350 markers to the actors face and track the marker movement with high resolution cameras. This has been used on movies such as The Polar Express and Beowulf to allow an actor,to drive the facial expressions of several different characters.
Active LED Marker technology is currently being used to drive facial animation in real-time to provide user feedback.

Markerless

Markerless technologies use the features of the face such as nostrils, the corners of the lips and eyes, and wrinkles and then track them.These vision based approaches also have the ability to track pupil movement, eyelids, teeth occlusion by the lips and tongue, which are obvious problems in most computer animated features. Typical limitations of vision based approaches are resolution and frame rate, both of which are decreasing as issues as high speed, high resolution CMOS cameras become available from multiple sources.

References :

http://en.wikipedia.org/wiki/Avatar_%282009_film%29#Visual_effects
http://en.wikipedia.org/wiki/Motion_capture
http://en.wikipedia.org/wiki/Facial_motion_capture