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Message: <blockquote data-quote="sihina_lahiru" data-source="post: 7400837" data-attributes="member: 149577">Motion capture, motion tracking, or mocap are terms used to describe the process of recording <a href="http://en.wikipedia.org/wiki/Motion_%28physics%29" target="_blank">movement</a> and translating that movement onto a digital model. It is used in <a href="http://en.wikipedia.org/wiki/Military_science" target="_blank">military</a>, entertainment, sports, and medical applications. In <a href="http://en.wikipedia.org/wiki/Filmmaking" target="_blank">filmmaking</a> it refers to recording actions of human actors, and using that information to animate digital character models in 2D or 3D <a href="http://en.wikipedia.org/wiki/Computer_animation" target="_blank">computer animation</a>. When it includes face, fingers and captures subtle expressions, it is often referred to as performance capture.The procedure In motion capture sessions, movements of one or more actors are sampled many times per second, although with most techniques (recent developments from <a href="http://en.wikipedia.org/wiki/Weta_Digital" target="_blank">Weta</a> use images for 2D motion capture and project into 3D) motion capture records only the movements of the actor, not his/her visual appearance. This animation data is mapped to a 3D model so that the model performs the same actions as the actor. This is comparable to the older technique of <a href="http://en.wikipedia.org/wiki/Rotoscope" target="_blank">rotoscope</a>, such as the 1978 "<a href="http://en.wikipedia.org/wiki/The_Lord_of_the_Rings_%281978_film%29" target="_blank">The Lord of the Rings</a>" animated film where the visual appearance of the motion of an actor was filmed, then the film used as a guide for the frame by frame motion of a hand-drawn animated character. 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 <a href="http://en.wikipedia.org/wiki/Match_moving" target="_blank">match moving</a> or camera tracking.Advantages Motion capture offers several advantages over traditional <a href="http://en.wikipedia.org/wiki/Computer_animation" target="_blank">computer animation</a> of a 3D model: <ul> <li data-xf-list-type="ul">More rapid, even real time results can be obtained. In entertainment applications this can reduce the costs of keyframe-based animation. For example: <a href="http://en.wikipedia.org/wiki/Hand_Over" target="_blank">Hand Over</a></li> </ul><ul> <li data-xf-list-type="ul">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.</li> </ul><ul> <li data-xf-list-type="ul">Complex movement and realistic physical interactions such as secondary motions, weight and exchange of forces can be easily recreated in a physically accurate manner.</li> </ul><ul> <li data-xf-list-type="ul">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.</li> </ul><ul> <li data-xf-list-type="ul">Potential for free software and third party solutions reducing its costs</li> </ul>Disadvantages <ul> <li data-xf-list-type="ul">Specific hardware and special programs are required to obtain and process the data.</li> </ul><ul> <li data-xf-list-type="ul">The cost of the software, equipment and personnel required can potentially be prohibitive for small productions.</li> </ul><ul> <li data-xf-list-type="ul">The capture system may have specific requirements for the space it is operated in, depending on camera field of view or magnetic distortion.</li> </ul><ul> <li data-xf-list-type="ul">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.</li> </ul><ul> <li data-xf-list-type="ul">The initial results are limited to what can be performed within the capture volume without extra editing of the data.</li> </ul><ul> <li data-xf-list-type="ul">Movement that does not follow the laws of physics generally cannot be captured.</li> </ul><ul> <li data-xf-list-type="ul">Traditional animation techniques, such as added emphasis on anticipation and follow through, secondary motion or manipulating the shape of the character, as with <a href="http://en.wikipedia.org/wiki/Squash_and_stretch" target="_blank">squash and stretch</a> animation techniques, must be added later.</li> </ul><ul> <li data-xf-list-type="ul">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.</li> </ul>Applications <a href="http://en.wikipedia.org/wiki/Video_game" target="_blank">Video games</a> often use motion capture to animate athletes, martial artists, and other in-game characters.<a href="http://en.wikipedia.org/wiki/Motion_capture#cite_note-0" target="_blank">[1]</a> This has been done since the <a href="http://en.wikipedia.org/wiki/Atari_Jaguar" target="_blank">Atari Jaguar</a> CD-based game Highlander: The Last of the MacLeods, released in 1995. Movies use motion capture for CG effects, in some cases replacing traditional cel animation, and for completely <a href="http://en.wikipedia.org/wiki/Computer-generated_imagery" target="_blank">computer-generated</a> creatures, such as <a href="http://en.wikipedia.org/wiki/Jar_Jar_Binks" target="_blank">Jar Jar Binks</a>, <a href="http://en.wikipedia.org/wiki/Gollum" target="_blank">Gollum</a>, <a href="http://en.wikipedia.org/wiki/The_Mummy_%281999_film%29" target="_blank">The Mummy</a>, <a href="http://en.wikipedia.org/wiki/Peter_Jackson%27s_King_Kong" target="_blank">King Kong</a>, and the Na'vi from the film <a href="http://en.wikipedia.org/wiki/Avatar_%282009_film%29" target="_blank">Avatar</a>. <a href="http://en.wikipedia.org/wiki/Sinbad:_Beyond_the_Veil_of_Mists" target="_blank">Sinbad: Beyond the Veil of Mists</a> was the first movie made primarily with motion capture, although many character animators also worked on the film. In producing entire feature films with <a href="http://en.wikipedia.org/wiki/Computer_animation" target="_blank">computer animation</a>, the industry is currently split between studios that use motion capture, and studios that do not. Out of the three nominees for the 2006 <a href="http://en.wikipedia.org/wiki/Academy_Award_for_Best_Animated_Feature" target="_blank">Academy Award for Best Animated Feature</a>, two of the nominees (<a href="http://en.wikipedia.org/wiki/Monster_House_%28film%29" target="_blank">Monster House</a> and the winner <a href="http://en.wikipedia.org/wiki/Happy_Feet" target="_blank">Happy Feet</a>) used motion capture, and only <a href="http://en.wikipedia.org/wiki/Walt_Disney_Pictures" target="_blank">Disney</a>·<a href="http://en.wikipedia.org/wiki/Pixar" target="_blank">Pixar's</a> <a href="http://en.wikipedia.org/wiki/Cars_%28film%29" target="_blank">Cars</a> was animated without motion capture. In the ending credits of <a href="http://en.wikipedia.org/wiki/Pixar" target="_blank">Pixar's</a> film <a href="http://en.wikipedia.org/wiki/Ratatouille_%28film%29" target="_blank">Ratatouille</a>, a stamp appears labelling the film as "100% Pure Animation -- No Motion Capture!" Motion capture has begun to be used extensively to produce films which attempt to simulate or approximate the look of live-action cinema, with nearly photorealistic digital character models. <a href="http://en.wikipedia.org/wiki/The_Polar_Express_%28film%29" target="_blank">The Polar Express</a> used motion capture to allow <a href="http://en.wikipedia.org/wiki/Tom_Hanks" target="_blank">Tom Hanks</a> to perform as several distinct digital characters (in which he also provided the voices). The 2007 adaptation of the saga <a href="http://en.wikipedia.org/wiki/Beowulf_%282007_film%29" target="_blank">Beowulf</a> animated digital characters whose appearances were based in part on the actors who provided their motions and voices. James Cameron's <a href="http://en.wikipedia.org/wiki/Avatar_%282009_film%29" target="_blank">Avatar</a> used this technique to create the Na'vi that inhabit Pandora. <a href="http://en.wikipedia.org/wiki/The_Walt_Disney_Company" target="_blank">The Walt Disney Company</a> has announced that it will distribute <a href="http://en.wikipedia.org/wiki/Robert_Zemeckis" target="_blank">Robert Zemeckis</a>'s <a href="http://en.wikipedia.org/wiki/A_Christmas_Carol_%282009_film%29" target="_blank">A Christmas Carol</a> and <a href="http://en.wikipedia.org/wiki/Tim_Burton" target="_blank">Tim Burton</a>'s <a href="http://en.wikipedia.org/wiki/Alice_in_Wonderland_%282010_film%29" target="_blank">Alice in Wonderland</a> using this technique. Disney has also acquired Zemeckis' <a href="http://en.wikipedia.org/wiki/ImageMovers_Digital" target="_blank">ImageMovers Digital</a> that produces motion capture films. Television series produced entirely with motion capture animation include <a href="http://en.wikipedia.org/wiki/Et_Dieu_cr%C3%A9a..._Laflaque" target="_blank">Laflaque</a> in Canada, <a href="http://en.wikipedia.org/wiki/Sprookjesboom" target="_blank">Sprookjesboom</a> and <a href="http://nl.wikipedia.org/wiki/Cafe_de_Wereld" target="_blank">Cafe de Wereld</a> in The Netherlands, and <a href="http://en.wikipedia.org/wiki/Headcases" target="_blank">Headcases</a> in the UK. <a href="http://en.wikipedia.org/wiki/Virtual_Reality" target="_blank">Virtual Reality</a> and <a href="http://en.wikipedia.org/wiki/Augmented_Reality" target="_blank">Augmented Reality</a> allow users to interact with digital content in real-time. This can be useful for training simulations, visual perception tests, or performing a virtual walk-throughs in a 3D environment. Motion capture technology is frequently used in <a href="http://en.wikipedia.org/wiki/Digital_puppetry" target="_blank">digital puppetry</a> systems to drive computer generated characters in real-time. <a href="http://en.wikipedia.org/wiki/Gait_analysis" target="_blank">Gait analysis</a> is the major application of motion capture in <a href="http://en.wikipedia.org/wiki/Clinical_medicine" target="_blank">clinical medicine</a>. Techniques allow clinicians to evaluate human motion across several biometric factors, often while streaming this information live into analytical software. During the filming of James Cameron's <a href="http://en.wikipedia.org/wiki/Avatar_%282009_film%29" target="_blank">Avatar</a> all of the scenes involving this process where directed in realtime using a screen which converted the actor setup with the motion costume into what they would look like in the move making it easier for Cameron to direct the movie as it would be seen by the viewer. This method allowed Cameron to view the scenes from many more views and angles not possible from a pre-rendered animation. He was so proud of his pioneering methods he even invited <a href="http://en.wikipedia.org/wiki/Steven_Spielberg" target="_blank">Steven Spielberg</a> and <a href="http://en.wikipedia.org/wiki/George_Lucas" target="_blank">George Lucas</a> on set to view him in action.Methods and systems Motion tracking or motion capture started as a photogrammetric analysis tool in biomechanics research in the 1970s and 1980s, and expanded into education, training, sports and recently <a href="http://en.wikipedia.org/wiki/Computer_animation" target="_blank">computer animation</a> for <a href="http://en.wikipedia.org/wiki/Television" target="_blank">television</a>, <a href="http://en.wikipedia.org/wiki/Film" target="_blank">cinema</a> and <a href="http://en.wikipedia.org/wiki/Video_game" target="_blank">video games</a> as the technology matured. A performer wears markers near each joint to identify the motion by the positions or angles between the markers. Acoustic, inertial, <a href="http://en.wikipedia.org/wiki/LED" target="_blank">LED</a>, magnetic or reflective markers, or combinations of any of these, are tracked, optimally at least two times the frequency rate of the desired motion, to submillimeter positions.Optical systems Optical systems utilize data captured from image sensors to <a href="http://en.wikipedia.org/wiki/Triangulation" target="_blank">triangulate</a> the 3D position of a subject between one or more cameras calibrated to provide overlapping projections. Data acquisition is traditionally implemented using special markers attached to an actor; however, more recent systems are able to generate accurate data by tracking surface features identified dynamically for each particular subject. Tracking a large number of performers or expanding the capture area is accomplished by the addition of more cameras. These systems produce data with 3 degrees of freedom for each marker, and rotational information must be inferred from the relative orientation of three or more markers; for instance shoulder, elbow and wrist markers providing the angle of the elbow.Passive markers  <a href="http://en.wikipedia.org/wiki/File:MotionCapture.jpg" target="_blank"><img src="http://upload.wikimedia.org/wikipedia/en/thumb/7/73/MotionCapture.jpg/220px-MotionCapture.jpg" alt="" class="fr-fic fr-dii fr-draggable " style="" /></a>  <a href="http://en.wikipedia.org/wiki/File:MotionCapture.jpg" target="_blank"><img src="http://bits.wikimedia.org/skins-1.5/common/images/magnify-clip.png" alt="" class="fr-fic fr-dii fr-draggable " style="" /></a> A dancer wearing a suit used in an optical motion capture system    <a href="http://en.wikipedia.org/wiki/File:Motion_capture_facial.jpg" target="_blank"><img src="http://upload.wikimedia.org/wikipedia/commons/thumb/9/95/Motion_capture_facial.jpg/220px-Motion_capture_facial.jpg" alt="" class="fr-fic fr-dii fr-draggable " style="" /></a>  <a href="http://en.wikipedia.org/wiki/File:Motion_capture_facial.jpg" target="_blank"><img src="http://bits.wikimedia.org/skins-1.5/common/images/magnify-clip.png" alt="" class="fr-fic fr-dii fr-draggable " style="" /></a></blockquote>

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