Motion Capture

We propose a new method for extracting key frames from a motion capture sequence. Our proposed approach consists of two steps. In the first step, we propose a new metric, curve saliency, for motion curves that specifies the important frames of the motion. In the second step, we detect the final key frames by clustering the computed important frames. As a result of our experimental results, on the average, by using only 3.7% of all frames as key frames, we can represent the captured motion sequence

In this paper we respond to the theme of real-time virtual performance that generates ways to increase embodied and spatial knowledge in the contexts of theatre history, scholarship and related performer education. Through discussing a series of international and inter-institutional collaborations on a project called VIMMA, primarily funded by the Finnish funding agency for technology and innovation TEKES and led by the Centre for Practice as Research in  Theatre T7 at the University of Tampere (Finland), we share the results of investigating real time modes of performing through revised engagements with digital 3D models of interactive performance environments.  These environments were designed to enable experiments with embodied agencies, transformations, transgressions and medialities (in-between states of adaption or contrast) that inform spatial enquiries into historical performance venues. Along with sharpening our current views on how to approach past performances, the digital production, training and performance formats employed can be used as emergent elements within new performative contexts, such as open game environments, complex non-human character scenarios and extended narrative elements of play.

Many causes can be at the origin of hip osteoarthritis (e.g., cam/pincer impingements), but the exact pathogenesis for idiopathic osteoarthritis has not yet been clearly delineated. The aim of the present work is to analyze the consequences of repetitive extreme hip motion on the labrum cartilage. Our hypothesis is that extreme movements can induce excessive labral deformations and lead to early arthritis. To verify this hypothesis, an optical motion capture system is used to estimate the kinematics of patient-specific hip joint, while soft tissue artifacts are reduced with an effective correction method. Subsequently, a physical simulation system is used during motion to compute accurate labral deformations and to assess the global pressure of the labrum, as well as any local pressure excess that may be physiologically damageable. Results show that peak contact pressures occur at extreme hip flexion/abduction and that the pressure distribution corresponds with radiologically observ...

Classical film theory topics, such as the divide between live action and animation, the definition of cinematic performance, and the configuration and impact of the star system continue to shape – while also being reshaped by – discourse on animation labor in the digital age. Focusing on motion capture in contemporary Hollywood, the first part of this article historicizes and examines the diminishment of the animators’ contribution to this filmmaking process in promotional materials and public discussions, and the accompanying overemphasis on the star persona’s performance. In doing so, it aims to contextualize and shed light on the practices and imperatives that determine current labor policies and power dynamics in the industry. The second part introduces questions
of gender relations and gender-based hierarchies of representation into the discussion of motion and performance capture’s labor climate. In order to highlight and reflect on the ambivalence of the motion capture industry’s labor politics, it offers a feminist reading of a distinct, yet related form of disenfranchisement in motion-capture filmmaking, namely digital voyeurism and the objectification of the female performer in films such as Beowulf (Robert Zemeckis, 2007) and
Avatar (James Cameron, 2009), and video games such as Beyond: Two Souls (Quantic Dream, 2013). Finally, by highlighting such interrelated policies of marginalization and erasure of labor, the author aims to emphasize the inadequacy of describing motion capture as a collaborative process
and to call for a reconceptualization of the critical approaches towards its study.

Abstract. A framework is outlined that can be employed to obtain gender and other characteristics of the agent from human motion patterns and subsequently use this information to synthesize motion with particular, well-defined biological and psychological attributes. The proposed model is based on the statistics of a data base of motion capture data. Based on linearization of the motion data, a motion space is defined which is spanned by the first few principal components obtained from the data base of input walkers. Using ...

While an actor's performance in a stage play may be seen as a continuous and unmediated form of acting, an actor's performance in a film is constructed through shot framing, editing, effects work, and other cinematic apparatuses. With the advent of digital filmmaking, constructed performances have become more complex and nuanced, especially through the use of motion capture. This research explores how we frame acting within a motion capture context-and specifically, how this affects our larger understanding of what is acting and how acting can be constructed. What does acting become when the product of acting starts as data and finishes as computer-generated images that may only tangentially resemble the actor's "original" performance? Is the source actor solely responsible for the performance we see on screen, or should other people within the production pipeline receive credit for their creative contributions to the finished acting result? How do we understand the act of acting in motion capture? Through consolidating and linking theoretical and practical considerations of acting in motion capture, this paper proposes a number of ways to conceive of acting and presence within a virtual acting context.

This work describes a method that passively assesses basic walker-assisted gait characteristic, including heel strikes, toe-off events, as well as stride time, double support and right & left single support phases using only force-moment measurements from the walker's handles. The passively derived gait characteristics were validated against motion capture gait analysis and showed good correlations. This research is part of an effort that aims to identify user intent, from measuring forces and moments exerted on the handles of the walker as well as from perceiving the environment, and to incorporate identified intent into a passive shared steering control system for the walker. The primary focus of the work leading to This work is to identify the double support phase, and to engage the steering control at the beginning of this phase to maximize the user's stability. However, the application of the method presented and the instrumented walker can be extended to longitudinal o...

Limited hip extension mobility has been proposed as a possible cause of both increased anterior pelvic tilt and subsequent exaggerated lumbar lordosis during walking and running. The purpose of the present study was to examine the coordinated sagittal plane kinematic patterns of the hip and pelvis during walking and running in a substantial group of adult recreational runners. The kinematics of 73 healthy adult runners (age: 34+/-11years) were examined on an instrumented treadmill at self-selected walking and running speeds using a three-dimensional motion capture system. Although stride length increased considerably from walking to running, the range of hip extension utilized during running was not significantly greater than that during walking. Thigh extension and anterior pelvic tilt were significantly greater during running than walking. Also, a significant positive correlation was found between hip extension and anterior pelvic tilt during both walking and running, indicating that anterior pelvic tilt was greater in subjects that displayed reduced utilized peak hip extension. Thus, compensations for the increased stride length during running seem to occur at the pelvis, and presumably in the lumbar spine, rather than at the hip. Considering the association between anterior pelvic tilt and lumbar lordosis, the present findings may have clinical relevance regarding the prevention and treatment of hamstring injuries and of injuries to the lumbar spine.

(from editor's introduction): "...Alla Gadassik continues the focus on new technologies, moving beyond discussing CGI's function in bringing the ghost to (nonorganic) life to explore the way animation is itself, to an ever greater degree, a ghostly technique that threatens to erase or spectralize the bodily presence of the animator."

This thesis comprehends the appeal in motion capture animation. The problem in this study is that many books deal only with the definition of the appeal from the perspective of conventional animation, therefore, a phenomenological study was conducted. There are eight participants who are involved in this study to obtain the data. The study objectives are to study the problem of 'uncanny valley' in the movement of motion capture animation, examine the success of using the markerless technique in animation production and investigate the benefit of using motion capture in animation. The finding from this study are that motion capture do not have its appeal included in the animation because of the phenomenon of 'uncanny valley' that contributes to the animated character to be moving in the inappropriate way with regard to its visual design. Besides, the use of markerless technique, in general, does make the character moves accordingly to the human actor but remains inaccurate. Additionally, staging is one of the animation principles that has become the theme of the benefit in using motion capture. It helps in providing flexibility to form a desired look of cinematography. Nevertheless, the researcher hopes that more digital animating techniques can be produced like the animating technique using the simulation of marionette upon the animation character in order to have more perspective in studying the appeal in animation.

The final year project can be viewed via this link: https://youtu.be/31bP2uR7ilw

It is often postulated that an increased hip to shoulder differential angle (`X-Factor') during the early downswing better utilises the stretch-shorten cycle and improves golf performance. The current study aims to examine the potential relationship between the X-Factor and performance during the tee-shot. Seven golfers with handicaps between 0 and 10 strokes comprised the low-handicap group, whilst the high-handicap group consisted of eight golfers with handicaps between 11 and 20 strokes. The golfers performed 20 drives and three-dimensional kinematic data were used to quantify hip and shoulder rotation and the subsequent X-Factor. Compared with the low-handicap group, the high-handicap golfers tended to demonstrate greater hip rotation at the top of the backswing and recorded reduced maximum X-Factor values. The inconsistencies evident in the literature may suggest that a universal method of measuring rotational angles during the golf swing would be beneficial for future studies, particularly when considering potential injury.

The current, system-specific countermeasures to space deconditioning have limited success with the musculoskeletal system in long duration missions. Artificial gravity (AG) that is produced by short radius centrifugation has been hypothesized as an effective countermeasure because it reintroduces an acceleration field in space; however, AG alone might not be enough stimuli to preserve the musculoskeletal system. A novel combination of AG coupled with one-legged squats on a vibrating platform may preserve muscle and bone in the lower limbs to a greater extent than the current exercise paradigm. The benefits of the proposed countermeasure have been analyzed through the development of a simulation platform. Ground reaction force data and motion data were collected using a motion capture system while performing one-legged and two-legged squats in 1-G. The motion was modeled in OpenSim, an open-source software, and inverse dynamics were applied in order to determine the muscle and reaction forces of lower limb joints. Vibration stimulus was modeled by adding a 20 Hz sinusoidal force of 0.5 body weight to the force plate data. From the numerical model in a 1-G acceleration field, muscle forces for quadriceps femoris, plantar flexors and glutei increased substantially for one-legged squats with vibration compared to one- or two-legged squats without vibration. Additionally, joint reaction forces for one-legged squats with vibration also increased significantly compared to two-legged squats with or without vibration. Higher muscle forces and joint reaction forces might help to stimulate muscle activation and bone modeling and thus might reduce musculoskeletal deconditioning. These results indicate that the proposed countermeasure might surpass the performance of the current space countermeasures and should be further studied as a method of mitigating musculoskeletal deconditioning.► Musculoskeletal deconditioning is a serious risk during long duration space missions. ► A countermeasure combining artificial gravity, squats, and vibration is analyzed. ► Numerical model developed to get muscle and joint dynamics during the countermeasure. ► Countermeasure provided higher muscle activation and joint forces than using iRED.

This contribution surveys strategies for analyzing highly coordinated forms of collaborative dance improvisation, based on tango argentino. Specifically, we take interest (a) in micro-coordination at the <1 s timescale in dance elements
such as steps or rotations, (b) in meso-scale patterns of 2–8 step “figures”, and (c) in general enabling macro-patterns maintained throughout, a kind of “grammar” of tango. Across these timescales, dancers supply individual action-readiness,
dynamic stability, proper form and connectivity, while jointly “managing” structures of interpersonal coordination such as enabling configurations. Our study engages qualitative and quantitative methods in a dialogue. Starting with micro-genetic elicitation interviews, dancers reported ideomotor concepts, perceptual triggers, and didactic imagery. Besides general (e.g. postural) habits, task-specific forms or techniques, and attentional foci, this yields insights into the
interlocking contributions and information flow between tango leaders and followers within units as small as half-steps. The subjective data was then “frontloaded”
into a motion-capture study in which six expert couples, fitted with 2 × 21 light-point reflectors, executed various tango techniques. We developed kinematic indicators for individual and interpersonal coordination (degree of coupling, relative movement onset and action timing, role specifics); we also measured geometries underlying various tango tasks and style variations. The combined data suggests a micro-coordination model where dynamic interdependencies enable precise mutually adaptive action. The criss-crossing signals, e.g. when the increasing lability of
the leader’s torso triggers the follower’s leg extension at the beginning of a forward step, suggests task-, phase- and body-part specific contingencies whereby leaders
and followers micro-coordinate actions with respect to one another.

Performance Capture (PCap) is the process of capturing a continuous recording of an actor's movements and emotions using motion capture technology, typically in a 3D virtual world. This presents a somewhat unique situation for the actor in that they are challenged to imagine their virtual counterparts and a completely abstract, computer-generated world whilst delivering their performance. Central to this paper is the identification of the various implications that affect the actor's abilities during a performance by investigating professionals' experiences when using performance capture and through the exploration of the implications of performance capture in the creation of a short experimental animation.