Stick Figure Research Articles

BALLONES: A Ballet Animation Language

he use of computers in the arts has a wide and promising future, particularly in the area of dance. One of the more recent developments in computer science, that of computer graphics, has been directed towards providing dancers with a set of computer tools to aid them in their work, and its development has been spectacularly fast and exciting. Michael Noll was the first to use computer animation for dance. His stick-figure representations of dancers appeared on a three-dimensional (3D) stereographic display and the choreographer controlled these figures via buttons on the console. The system was designed for use by the choreographer when planning stage positions and directions. Together with the use of a dance-notation editor, a whole ballet or sequence could be planned and pieced together [1 ]. Several systems for the display of human movement base their animations strictly on stick figures. These include systems by Withrow in 1970 [2], Savage and Officer in 1977 [3] and Barenholz, Wolofsky, Ganapathy, Calvert and O'Hara in 1977 [4]. In addition, body animations have been modelled by cylinders, ellipsoids and spheres. Evans and Potter, in 1976 and 1975, used cylinders as their basis-however, the primary difficulty with this approach is that the planar end caps must be smoothed at the joints [5]. In 1978 Badler, Smoliar and Weber used overlapping spheres to model the human body. The figure produced is known as Bubbleman [6]. In 1974 HerbisonEvans used ellipsoids to model the human body [7]. The project BALLONES uses this ellipsoid representation of the human body. Eddie Dombrower developed a computer program that will notate, edit and create dances. A light pen is used to move the parts of a silhouette figure that can be viewed from many angles [8]. Most recently, Zhu Xiqun has designed and implemented a dance editor and animator. The system can edit dance and music scores, translate a position drawn in another window into scores and animate the score accompanied by music. However, the system requires the dances to be described using a new specialised notation system, rather than an existing dance notation [9]. This paper outlines the design and implementation of a system for classical ballet dancers. The design and implementation of the system was undertaken as an honours project in Computer Science at the University of Sydney. It converts an enchainement (chain of steps) expressed in the French terminology of classical ballet used by dancers and choreographers, to a Numerical Utility Displaying Ellipsoid Solids (NUDES) program, a mathematical command language for computer animation [10]. The output is viewed using Show, an animation display program, which animates the movements. Thus users can work with their own terminology and input this to produce animation of an enchane-

SMARTWheels: development and testing of a system for measuring manual wheelchair propulsion dynamics.

The purpose of this project was to develop a system for dynamically sensing pushrim propulsion forces and torques and to collect kinetic data with the device. A system was developed to detect the forces and torques applied to the wheelchair pushrim, record, store, and process the measured data, and display the kinetic information for analysis. Ten adults, including four male wheelchair users, three ambulatory men, and three ambulatory women, pushed a wheelchair with the SMARTWheel on a dynamometer while their kinematics were videotaped. The kinetic data collected with our wheel were correlated with stick figure representations of digitized kinematic data obtained through video analysis. The close agreement between the kinetic results and the Kinematic results provided a temporal validation of the ability of the wheel to detect forces and torques applied to the wheelchair pushrim. The recorded forces and torques were in agreement with previously reported magnitudes.

A Postural Model of Balance-Correcting Movement Strategies

The patterns of joint torques and movement strategies underlying human balance corrections were examined using a postural model. Two types of support-surface perturbation, dorsiflexion rotation (ROT) and rearward translation (TRANS), were employed. These two perturbations were adjusted to produce similar profiles of ankle dorsiflexion in order to obtain information on the role of lower leg proprioceptive inputs on triggering balance corrections. In addition, the dependence of balance control on head angular and linear accelerations was investigated by comparing the responses of normal and vestibularly deficient subjects under eyes-closed and eyes-open conditions. Differences in ROT and TRANS movement strategies were examined in three ways First, the amplitude and polarity of active joint torques were analysed. These were obtained by altering joint torques applied to a postural model until movements of the model accurately duplicated those of measured responses. Second, the pattern of body-segment angular movements depicted by stick figures moving in response to the computed joint torques was investigated. Third, the peak amplitude and patterns of crosscorrelations between joint torques were measured. Active ankle, knee, and hip joint torques computed for normal subjects rotated the body forward for ROT. In the case of TRANS, computed active torques in normals were of opposite polarity to those of ROT and reversed the forward motion of the body. Subjects with vestibular deficits had lower amplitude torques for ROT and failed to counter the platform rotation. Hip torques for TRANS in vestibular deficient subjects were of opposite polarity to those of normal subjects and resulted in excessive forward trunk rotation. Normally, neck torques acted to stabilize the head in space when trunk angular velocity peaked. Vestibular deficient subjects displayed head movements in response to ROT similar to those generated when neck torques were absent. For TRANS, these same subjects exhibited overcompensatory neck torques. Stick figures of normal responses indicated a stiffening of the body into a leg and a trunk-head link for ROT and a flexible multilink motion for TRANS. Likewise, normal response strategies, defined by using crosscorrelations of joint torques, differed for ROT and TRANS. All joint torque crosscorrelations were significant for TRANS. Neck torques led those of all other joint torques by 40 ms or more, and hip joint led ankle torques by 30 ms. Joint torque correlations for ROT were organised around hip and ankle torques without a major correlation to neck torques. Fundamental changes in all torque crosscorrelations occurred for vestibularly deficient subjects under both eyes-open and eyes-closed conditions.(ABSTRACT TRUNCATED AT 400 WORDS)

Knowledge-guided visual perception of 3-D human gait from a single image sequence

A computer vision method is presented to determine the 3-D spatial locations of joints or feature points of human body from a film recording the human motion during walking. The proposed method first applies the geometric projection theory to obtain a set of feasible postures from a single image, then it makes use of the given dimensions of the human stick figure, physiological and motion-specific knowledge to constrain the feasible postures in both the single-frame analysis and the multi-frame analysis. Finally a unique gait interpretation is selected by an optimization algorithm. Computer simulations are used to illustrate the ideas presented. >

Construction of Three-Dimensional Stick Figures from Branched DNA

Stable DNA branched junction molecules can be used as the building blocks for stick-figures in which the edges are double-helical DNA and the vertices correspond to the branch points of the junctions. Sticky-ended cohesion is used to direct the association of individual branched complexes. The sequences of these molecules are assigned by a sequence-symmetry minimization procedure. Successful ligation experiments include the oligomerization of individual three-arm and four-arm junctions, the assembly of a quadrilateral from four junctions with different sticky ends, and the recent construction of a molecule with the connectivity of a cube. Possible applications include the assembly of molecular electronic devices, the formation of macromolecular-scale zeolites to host biological complexes for diffraction analysis, and the development of new catalysts.

The use of branched DNA for nanoscale fabrication

An approach to molecular nanotechnology is presented that utilizes branched DNA molecules to form stick figures. These branched molecules are directed to associate in a particular fashion by utilizing the addressability of DNA sticky ends. The sequences of molecules are designed using an algorithm that minimizes sequence symmetry. This system has been used to construct macrocycles, a DNA quadrilateral, a molecule with the connectivity of a cube and a single-stranded DNA knot. Possible uses for this system include the construction of macromolecular zeolites for structure determination by diffraction, the assembly of new catalysts, the solubilization and delivery of drugs, and the assembly of molecular electronic devices.

Promoting Generalisation of Appropriate Behaviour Across Special and Mainstream Settings: A case study

Summary A young child with an intellectual impairment was trained in a self management procedure in an attempt to ameliorate inappropriate classroom behaviours which were preventing his full integration into mainstream classes. A structured programme utilising countoons (stick figure drawings) to demonstrate specific behaviour to be self monitored was introduced in the special education facility where the participant received the majority of his education. Coloured stickers which were highly reinforcing were self administered by the participant when he exhibited the desired behaviours. Observations carried out in the special education facility and in a mainstream class to test for generalisation revealed reductions in the frequency of inappropriate behaviours in both settings. Follow up observations revealed behaviour maintenance in the special education facility whilst further reductions were recorded in the mainstream class.

Kineman: A Microcomputer-based Video Digitising System for Movement Analysis

Summary This paper describes and discusses a video-digitising system which uses a suite of microcomputer programs (KINEMAN) that has been developed and used to carry out kinematic analyses of human motor action. The equipment is relatively low cost and consists of a video camera, a high quality U-matic or Super VHS videotape recorder, a monitor and microcomputer (BBC Master or PC using MS. DOS). Mouse-driven software enables the acquisition of X-Y co-ordinates for reference points on the joints of the subject which are stored on disk, then edited and converted to ‘real’ values. Further programs from the suite are used to calculate and list angles, limb velocities, and limb accelerations. It also has facilities for data smoothing, graphing, and presenting sequences of stick figures. The accuracy of the system as a means of generating two-dimensional kinematic data has been demonstrated and several studies have shown that reliable results can be obtained with minimal training and without technical assistance.

Operator performance in myoelectric control of a multifunction prosthesis stimulator

In this paper, a microcomputer-based system is described which facilitates the evaluation of different myoelectric control strategies. The system is based on an IBM-PC/AT microcomputer which generates and develops tracking targets, processes and displays the operator's response, and computes tracking performance. The dynamics of the prosthetic elbow, hand, and forearm are simulated in software which drives a stick figure in response to the operator's input. Performance is measured in terms of integral absolute error in target-response match. Control strategies to simulate different systems are easily modified through software and are evaluated under identical conditions. As a test of this evaluation system and to obtain some comparative data on control strategies, four strategies which are either in use or proposed for use are evaluated. The test procedure is divided into a control training session and a control evaluation session. Data collected from groups of three normally-limbed subjects per strategy over a period of five control evaluation sessions are presented. The results of this evaluation are discussed and improvements in the evaluation system suggested.

Morphologies of rabbit retinal ganglion cells with complex receptive fields.

Ganglion cells that had complex receptive field properties, namely, On-Off and On direction-selective cells, orientation-selective cells, local edge detectors, and uniformity detectors (suppressed by contrast cells) were recorded in an isolated superfused rabbit eyecup preparation. Cells were first classified by their characteristic extracellular responses to manually controlled stimuli similar to those which have been used in previous in vivo studies. Ganglion cells were then impaled, confirmed in identity by intracellular recording, and iontophoretically injected with horseradish peroxidase for staining. Twenty-two ganglion cells, which included members of all the major classes mentioned above, were recovered from the visual streak or near periphery. All recovered cells were drawn in camera lucida from flat-mounted retinas and entered into a computer as two-dimensional stick figures; nearly all were three-dimensionally reconstructed to determine the level and manner of dendritic ramification in the inner plexiform layer (IPL). The location of ganglion cell dendrites in sublaminar regions of the IPL was found to be consistent with the hypothesis of a division of the IPL into excitatory On (proximal) and Off (distal) sublaminae, with some qualifications for particular classes. Each of the complex receptive field ganglion cell classes exhibited a distinctive three-dimensional dendritic arborization pattern uniquely associated with that physiological class.

Algorithms for the segmental motor innervation of the extremities : Peck D, Brower TD. Am Surg 1987; 53: 270–273

The pattern of the segmental motor innervation to the extremities is reflected in the kinematics of their joint linkages. More proximally located joints have more complex movements and are controlled by more spinal cord levels than more distal joints with simpler movements. More proximally located joints are also controlled by more cranially located groups of spinal cord levels while more distal ones are innervated by more caudally located groups. Algorithms are presented that summarize these principles in the form of two simple, concise charts and a stick figure. The cord levels given by the algorithms for the innervation of any particular muscle are in good general agreement with recognized authorities. In addition, these algorithms are easily learned and readily applied to clinical problems by placing the patient in the position assumed when playing the piano or operating an automobile. In this posture, the most cranial two spinal cord levels of a group controlling a joint are responsible for "upward" motion of that joint and the most caudal two or three control "downward" motion thereof.

Handprinted symbol recognition system

In this paper the design characteristics of a recognition system for unconstrained handprinted symbols are described. The targeted symbols and accuracy requirements from a mapping and charting environment posed problems requiring the development of new OCR techniques. The recognition system employs smart thinning algorithms to produce centerline thinned stick figure images from raster scanned characters. The recognition logic interacts with the feature extraction algorithms to extract just those topological, geometrical and local measurements that are needed to identify the character or to reject the character as unrecognizable. Results from a numeric character data base consist of some 7000 numerals collected from a broad spectrum of sources and yield an efficiency rate of 97%. Substitution error rate is 0.3% and rejection rate is 2.7%. Preliminary results for the recognition of alphabetic characters are also discussed.

A size-congruency effect in memory for visual shape.

In five experiments, visual shapes were shown at either a small or a large size for study in the learning phase of a recognition memory experiment. Later, in the test phase, recognition memory was tested in anold-new paradigm in which an equal number of new shapes were mixed at random with previously seen shapes. Half of theold shapes were shown at the same size as in the learning phase, whereas half were shown at the other size. In every experiment, shapes tested at the same size as shown in the learning phase were recognized more quickly and more accurately than shapes tested at a different size. This size-congruency effect was found for line drawings of natural objects and for unfamiliar shapes (i.e., blobs and stick figures). Furthermore, the magnitude of the size-congruency effect depended on the degree of discrepancy between the learning size and the test size. Together, the results suggest that visual shape memory can be sensitive to the size at which patterns are originally encoded, and that the speed and accuracy of recognition memory is influenced by the size of a shape.

Contralateral Compensation with Knee Impairment

Knee motion of four healthy teenagers was unilaterally impaired by means of cast braces. Computerized analysis from video recording of walking was used to study the compensatory effects and to compare them with six patients. Restricted knee flexion caused little change in stance-phase knee motion on the restricted side. The unimpaired knee displayed exaggerated stance phase flexion and phase shifts, which in turn produced pelvic vaulting. The forces on the braces were high. Impairments to extension produced bilateral crouch without loss of flexion extension patterns within the limits of the impairment. Fatigue was more prominent than with blocks to flexion. Circumduction was found to be overrated as a compensation for stiff-leggedness. Lateral shift to the well side, combined with freezing of the well-side stance adduction, was a frequently used effective clearance mechanism. Phasic changes in motion of many body parts may combine to produce low-level pelvic displacement, especially when clinical weakness is present. Shortened stride length is the most sensitive indicator of this phenomenon. Graphs of individual joint motion do not easily convey the important phasic relationships that are fundamental to that motion and to the interpretation of its effects. Stick figures were better for analysis of this aspect of motion analysis, even though they are more subjective.

The biomechanics of lower extremity action in distance running.

The role of quantitative biomechanical measurements in the evaluation of the running patient is discussed. Many techniques are now available to provide insight into the external mechanics of lower extremity action during running, and results from such measurements are presented for symptom-free subjects at distance running speeds. Details of stride length, stride time, and foot placement are first presented followed by a discussion of kinematic data, including stick figures, angle-time graphs, and angle-angle diagrams for the sagittal plane motion of the hip, knee, and ankle joints. The measurement of rearfoot motion, as an approximation of coronal plane subtalar joint movements, is also discussed. Results from acceleration, force, and pressure measurements are considered, and the assertion is made that bilateral asymmetry in many of these measures is a fairly common finding. There are, at present, few reports in the literature of the application of biomechanical techniques to the evaluation of patients with running injuries. It is anticipated that there will be rapid developments in this area in the future and that this will provide considerable insight into the etiology, diagnosis, and treatment of running injuries.

Perception of biomechanical motions by infants: Implementation of various processing constraints.

Geometry informs us that there exist a large number of possible connectivity patterns consistent with a point-light display of a person walking. Yet there is only one pattern consistent with a "stick figure" representation of the human form, and that pattern is uniquely specified by those pairwise connections that remain locally rigid. In this study, sensitivity to local rigidity in biomechanical displays was investigated in 3- and 5-month-old infants. The results of Experiment 1 revealed that by 5 months of age, infants discriminate a locally rigid point-light walker display from one in which local rigidity is perturbed. In Experiment 2 we tested infants' sensitivity to the same stimuli when those stimuli were inverted. Contrary to the preceding experiment, the results revealed no evidence of discrimination. Taken together, these findings suggest that infants are sensitive to local rigidity in biomechanical displays but that this sensitivity is orientation specific. Possible mechanisms for this specificity are discussed in the context of additional constraints on the processing of biomechanical displays.

Perception of biomechanical motions by infants: implementation of various processing constraints.

Geometry informs us that there exist a large number of possible connectivity patterns consistent with a point-light display of a person walking. Yet there is only one pattern consistent with a "stick figure" representation of the human form, and that pattern is uniquely specified by those pairwise connections that remain locally rigid. In this study, sensitivity to local rigidity in biomechanical displays was investigated in 3- and 5-month-old infants. The results of Experiment 1 revealed that by 5 months of age, infants discriminate a locally rigid point-light walker display from one in which local rigidity is perturbed. In Experiment 2 we tested infants' sensitivity to the same stimuli when those stimuli were inverted. Contrary to the preceding experiment, the results revealed no evidence of discrimination. Taken together, these findings suggest that infants are sensitive to local rigidity in biomechanical displays but that this sensitivity is orientation specific. Possible mechanisms for this specificity are discussed in the context of additional constraints on the processing of biomechanical displays.

Ultramarine by Raymond Carver

Reviews 177 “clepsydra” becomes a physical metaphor for the passage of time: “Two identical pots, / one filled with water that trickles out of a hole / to fill the other below it.” Water islife, and water is time, and human life isa span of time: a cup running over or emptied in death. Using the no-nonsense approach of science but with a clarity free of jargon, Barnard remains acutely aware of her own use of figurative language and that of the sky-watchers. “Abstractions like these / need handles, a name, a color, a picture to tell us / this direction iseast, this north.” Metaphor translated the ways of the universe to man. It brought to life language and learning. So metaphor beats at the heart of poetry, ritual and religion. In “Song for the Millenium” : Life runs on and runs out, and time runs on and around, but measured by moons, by daylight and dark, by tides that rise and fall, and by feet that dance. DAVE ENGEL Rudolph, Wisconsin Ultramarine. By Raymond Carver. (New York: Random House, 1986. 128 pages, $13.95.) “Ultramarine” connotes deep blue sea water and the dark, deeper blue of the firmament where the mind wanders in dreams and the soul wanders in death. It also reminds you of the blues, and Raymond Carver’s Ultramarine is full of the blues to the same degree that is full of the sea and the firmament. It is a portrait of the artist in blue-grey middle-age, and it is blunt, simple and complex; in other words, a paradox. Carver’s poems are episodes from his life. They are stories told by an avuncular sort of fellow, sitting on his porch tying flies and spitting in the flower bed. This is amusing for the first dozen pages, until you begin to grow fond of him. Then the characters in his stories start to take on dimensions: his ex-wife; his children, who fill his mailbox with demands for money; his half crazy mother, who blames him when it snows; his drinking buddies. Eventually, the images from the poems become cinematic—one image leads to the next, and you keep turning pages to see what happens next as if you were reading an adventure novel. About the time you begin to think that these poems are not only simple, but simple-minded, Carver throws a hook into you—a line that is strikingly profound and beautifully stated. It’s like finding Uncle Lou, who works at the gas station when he’s not fishing, sitting on the porch reading Lao-Tse. There is something unsettling about this. Much of the strength of the poems isvisual, and at times it seems that Carver hides behind this strength until it becomes 178 Western American Literature a weakness. What is revealed doesn’t seem to be enough. The depth of the insights jar against the simplicity of the characters as drawn, including the character of the author himself. This may be an intended paradox, for the blue themes of Ultramarine—death, love, choice, and the nature of relation­ ships—tend to make simple stick figures of us all. STEVEN PUGMIRE Seattle, Washington Cadillac Desert: The American West and Its Disappearing Water. By Marc Reisner. (New York: Viking, 1986. 582 pages, $19.95.) Midway through the present century it was argued that reclamation services—the Army Corps of Engineers, the United States Reclamation Serv­ ice, plus various state agencies—would encourage small, family farms and thus the American Dream, by providing inexpensive water; as Don Villarejo has shown, precisely the opposite has occurred in California’s San Joaquin Valley, perhaps the world’smost thoroughly and precariously irrigated region, where massive corporate holdings have expanded and continue doing so. That was one small deception in a tapestry of self-serving projections and outright lies that have characterized the irrigation of the West. Marc Reisner takes on such absurdities—and far greater ones—writing powerfully and well about perhaps the single most important of western issues: the control of water and the dam-building hegemony. He reveals in this important book the degree to which water politics have taken on a life of their...

Interactive program for visualization and modelling of proteins, nucleic acids and small molecules

The graphics package Insight for the DEC VAX and Evans and Sutherland PS300, created as part of a joint university-industry research project, provides a broad set of capabilities which allow the user to display molecular models in stick figure and surface representation. The Insight program allows the user to model and manipulate proteins, nucleic acids and small molecules. The software accepts coordinate input from several possible sources and provides both a command and menu interface for manipulation of the graphics objects. The command language and program structure make it easy for the biochemist or molecular biologist to use.

Macromolecular design, nucleic acid junctions, and crystal formation.

The simplest form of macromolecular design involves the ligation of nucleic acids. Recent results on the concatenation of nucleic acid junctions show that these molecules can act as fairly rigid macromolecular valence clusters on the nanometer scale. These clusters can be joined to form closed stick figures in which each edge is double helical DNA or RNA and each vertex is a nucleic acid junction. The geometrical criteria for forming discrete-closed and periodic structures from these components are established. The helicity of each edge limits the possible structures that can be formed. The formation of a periodic array from nucleic acid junction building blocks is compared with the crystallization of molecular systems. This comparison leads to a new interpretation of the nature of order in the solid state for molecular crystals. The suggestion is made that the structure of a solid molecular system described by the fewest unique orthogonal (Fourier) components is the one which will be entropically favored, since it contains the least information. This is the crystalline state, with a small number of molecules per asymmetric unit. The free energy from the proposed entropic driving force responsible for this behavior is available, in principle, to correct small deviations from ideality in forming covalent crystals from nucleic acid junction components, as well as in non-bonded molecular systems. Nucleic acid junction periodic arrays provide an appropriate vehicle with which to test this interpretation.