Graphical Tasks Research Articles

A multiresolution framework for variational subdivision

Subdivision is a powerful paradigm for the generaton of curves and surfaces. It is easy to implement, computationally efficient, and useful in a variety of applications because of its intimate connection with multiresolution analysis. An important task in computer graphics and geometric modeling is the construction of curves that interpolate a griven set of points and minimize a fairness functional (variational design). In the context of subdivision, fairing leads to special schemes requiring the solution of a banded linear system at every subdivision step. We present several examples of such schemes including one that reproduces nonuniform interpolating cubic splines. Expressing the construction in terms of certain elementary operations we are able to embed variational subdivision in the lifting framework, a powerful technique to construct wavelet filter banks given a subdivision scheme. This allows us to extend the traditional lifting scheme for FIR filters to a certain class of IIR filters. Consquently, we how how to build variationally optimal curves and associated, stable wavelets in a straightforward fashion. The algorithms to perform the corresponding decomposition and reconstruction transformations are easy to implement and efficient enough for interactive applications.

Motor Perseverations: A Function of the Side and the Site of a Cerebral Lesion

Motor perseverations are commonly thought to be a sign of frontal lobe lesions, although they may also occur following lesions outside the frontal lobes. Moreover, differences in the type and frequency of motor perseverations between the two cerebral hemispheres have been suggested. Recurrent perseverations (repetition of a previous response to a subsequent stimulus) and continuous perseverations (abnormal prolongation of a current activity) are two different aspects of motor intentional disorders. The former have been associated with left hemispheric lesions, and the latter with right hemispheric lesions. To test this hypothesis, we examined 42 patients with single cerebral lesions of different locations: 22 right hemispheric (7 frontal and 15 extrafrontal) and 20 left hemispheric lesions (8 frontal and 12 extrafrontal), and healthy controls with a graphic task, allowing for analysis of these two types of motor perseverations. We found that (i) both types of perseverations increased significantly for all groups of patients compared to normal controls, except for recurrent perseverations in patients with right posterior lesions, (ii) there was no significant dissociation between the type of perseverations and the side of lesions, and (iii) there was a significant interaction between the type of perseveration, frontal versus extrafrontal location, and the side of a lesion, which is based on the tendency for recurrent perseverations to be increased in left posterior and right frontal lesions, and decreased in left frontal and right posterior lesions, as compared to continuous perseverations. These findings cast doubt about the predominant role of the frontal lobes for motor perseverations, but support the idea of hemispheric specialization in motor control which is, however, more complex than previously thought.

Lateralized spatial strategies in oscillating drawing movements.

Kinematic characteristics and lateral differences between two upper extremities were investigated in a unimanual graphic task involving fast and precise oscillating movements on the vertical plane. The spatial locations of sequential reversal points were used to calculate the pairs of angles, relative to the horizontal axis. The point biserial coefficient of correlation was used to analyze the difference between big and large angles and their sequence in each pair. Three main groups (A, B, and C) of performance models were distinguished in 132 tests by 33 strongly right-handed male subjects. Group A showed strong variation in vertical movement, Group B covariation in vertical and horizontal vectors, while Group C reflected independent variation of both vertical and horizontal directions. It is suggested that the movement strategies might reflect three different models of motor control involving coupling of an oscillator controlling pools of motoneurons which regulates horizontal movements with an oscillator controlling vertical movement (Groups A + B) or with nonoscillating control signal (Group B). It is argued that Group A represents the simplest strategy and only performance Type A met by the left hand.

Stress, neuromotor noise, and human performance: a theoretical perspective.

A new theory on stress and human performance is proposed in which physical and cognitive stressors enhance the level of neuromotor noise in the information-processing system. The neuromotor noise propagates in time and space. A 2nd assumption states that such noise facilitates easy tasks but disrupts complex tasks. In 4 experiments, 2 graphic tasks (number writing and graphic aiming) were crossed with 2 stressors (cognitive stress from a dual-task situation and physical stress in the form of loud auditory noise). Reaction time (RT), movement time (MT), and axial pen pressure were measured. In the RT phase, stress was predicted to lead to decreased RT with easy tasks and to increased RT with difficult tasks. In the execution phase, biomechanical adaptation to enhanced levels of noise was expected to manifest in higher levels of limb stiffness. In all 4 experiments, an increase of axial pen pressure with higher levels of stress evidenced the generality of biomechanical adaptation as a response to stress. RT and MT showed differential effects among the 4 experiments.

Adaptation of a reaching model to handwriting: how different effectors can produce the same written output, and other results.

This report shows how a model initially developed for the control of reaching can be adapted for the control of handwriting. The main problem addressed by the model is how people can produce essentially the same written output with different effectors (e.g., the preferred or nonpreferred hand, the foot, or even the mouth). The model is based on the assumption that writers strive for invariant graphic outputs when they write with different effectors, when they write on surfaces with different orientations, or when they write large or small script; such output invariance is an essential requirement for later recognition of the written result. Given this assumption, the question is how the motor system enables the relevant effectors to generate the necessary pen strokes. The adapted model provides one possible answer to this question. It is first fully working model of multijoint activity underlying writing and related graphic tasks. We describe how the model differs from other models developed in the past, and we review the model's strengths and weaknesses.

Fitts' law as the outcome of a dynamic noise filtering model of motor control

Studies into the real-time evolution of goal-directed movements have been strongly dominated by the view that movement time and other kinematic features are a direct reflection of on-line computational processes. Well-known examples of this position try to explain the logarithmic relation between the movement time of aiming movements and their demanded endpoint accuracy, as described by Fitts in 1954, by the use of centrally controlled servomechanisms and submovements. In the present article it is doubted whether such a strict cognitive approach can provide real understanding of the kinematics of aiming movements. An alternative, noise filtering model of motor control is presented proposing that the psychomotor system is an inherently noisy mechanical system for which spatial demands should be formulated in terms of a desired signal-to-noise ratio between goal-related propulsion of the limb (signal) and stochastic error (noise). Adequate movements would, from this point of view, result from the optimization between the application of muscle forces to the limb system and the noise reducing effects of biomechanical properties, such as stiffness, viscosity, or friction due to surface contact. At a theoretical level, the present approach is exemplified in a simulation model which takes into account the stochastic nature of the motor unit recruitment process and the noise filtering properties of a biomechanical limb. Empirical data acquired in a simulation study, as well as published data on eye-ball control during looking tasks and data on axial pen pressure control in graphic tasks, lend support to the view that adaptive control of muscular co-contraction is a relevant degree of freedom for the control of spatial accuracy.

Visuospatial difficulties and clumsiness: on the interpretation of conjoined deficits.

Sixteen children with motor difficulties and 16 controls, matched on age, gender and verbal I.Q., were assessed on the Test Of Motor Impairment, various graphic tasks and a measure of visuospatial discrimination. Poor perceptual and motor performance tended to co-occur but contrary to the visuospatial deficit account of clumsiness these abilities were uncorrelated even when attention was restricted to the less proficient children. There was no tendency for the control group's superiority in graphic reproduction to diminish when visual feedback was withheld. Some suggestions are offered concerning more appropriate methods for framing and testing causal deficit hypotheses.

Pupil Performance in Graphical Tasks and its Relationship to the Ability to Handle Variables

British Educational Research JournalVolume 20, Issue 2 p. 227-243 Pupil Performance in Graphical Tasks and its Relationship to the Ability to Handle Variables P. Swatton, Corresponding Author P. Swatton University of WarwickDepartment of Education, University of Warwick, West-wood, Coventry CV4 7AL, United KingdomSearch for more papers by this authorR. M. Taylor, R. M. Taylor Kingshurst City Technology College University of Warwick, SolihullSearch for more papers by this author P. Swatton, Corresponding Author P. Swatton University of WarwickDepartment of Education, University of Warwick, West-wood, Coventry CV4 7AL, United KingdomSearch for more papers by this authorR. M. Taylor, R. M. Taylor Kingshurst City Technology College University of Warwick, SolihullSearch for more papers by this author First published: April 1994 https://doi.org/10.1080/0141192940200207Citations: 23AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat Citing Literature Volume20, Issue2April 1994Pages 227-243 RelatedInformation

Ocean Drilling Program: Recent Highlights and Future Expeditions

During the past year, exploration of the deep ocean floor through scientific ocean drilling has yielded important results with respect to evolution of ocean crust and continental margins and paleoceanography. This paper describes the Ocean Drilling Program's (ODP's) scientific and technical achievements during its ninth year of field operations and discusses areas of future study.

Shared workspaces: how do they work and when are they useful?

We investigated the effect on synchronous communication of adding a Shared Workspace to audio, for three tasks possessing key representative features of workplace activity. We examined the content and effectiveness of remote audio communication between pairs of participants, who worked with and without the addition of the Workspace. For an undemanding task requiring the joint production of brief textual summaries, we found no benefits associated with adding the Workspace. For a more demanding text editing task, the Workspace initially hampered performance but, with task practice, participants performed more efficiently than with audio alone. When the task was graphical design, the Workspace was associated with greater communication efficiency and also changed the nature of communication. The Workspace permits the straightforward expression of spatial relations and locations, gesturing, and the monitoring and coordination of activity by direct visual inspection. The results suggest that, for demanding text-based tasks, or for complex graphical tasks, there are overall benefits in adding a visual channel in the form of a Workspace. These benefits occur despite the costs involved in attempting to coordinate activity with this unfamiliar form of communication. Our findings provide evidence for early claims about putative Workspace benefits. We also interpret these results in the context of a theory of mediated communication.

Inferring constraints from multiple snapshots

Many graphic tasks, such as the manipulation of graphical objects and the construction of user-interface widgets, can be facilitated by geometric constraints. However, the difficulty of specifying constraints by traditional methods forms a barrier to their widespread use. In order to make constraints easier to declare, we have developed a method of specifying constraints implicitly, through multiple examples. Snapshots are taken of an initial scene configuration, and one or more additional snapshots are taken after the scene has been edited into other valid configurations. The constraints that are satisfied in all of the snapshots are then applied to the scene objects. We discuss an efficient algorithm for inferring constraints from multiple snapshots. The algorithm has been incorporated into the Chimera editor, and several examples of its use are discussed.

Impact of gigabit network research on scientific visualization

Networks based on the High Performance Parallel Interface (HIPPI) will become the norm at Los Alamos National Laboratory. The ramification of such a high-speed networking paradigm on scientific visualization are enormous. Not only will scientists have the capability of networked framebuffer animation loops in their offices, but also the partitioning of graphics tasks between MIMD, SIMD, and specialized hardware will be feasible. Of course, as bandwidth increases, the problem size quickly grows to exceed whatever the limits are. For this reason, the investigation of gigabyte networks is currently underway at Los Alamos National Laboratory.

Analysis of actual and mental movement times in graphic tasks

This paper reports on a study of movement times and movement time variability of graphic gestures which were executed either physically or mentally. The results revealed that temporal parameters for actual as well as mental graphic movements in the same subject and for the same hand were very similar, irrespective of the writing amplitude. It is suggested that the programming of motor acts, whether they are physically executed or only virtually, share to a considerable extent the same timing mechanism.

Body-Image Dissatisfaction among American Male and Female College Students: A Computer-Based Graphical Approach

College students (56 women and 43 men) attending state colleges in the southwestern United States were tested for body-image dissatisfaction using a computer-based graphical body-image task. A reliable relationship between desired stature and desired body-image was observed for the women. Women of large stature showed a greater discrepancy between verbally reported desired stature and redrawn images of desired stature than women of average or smaller than average stature. No reliable discrepancy between desired body-image and verbally reported desired stature was shown by the men.

The Predictability of Cursor Control Device Performance Based on a Primitive Set of User Object-Oriented Cursor Actions

The ability to predict performance with a cursor control device on a complex task by measuring performance on a simple task would be useful in evaluating alternative input devices in many types of novel situations. A user would simply have to perform simple cursor movements with each candidate device, and predictions could be made of his/her performance with the devices on any given software application. Such an approach would reduce tedious trial and error procedures, as well as eliminate the time necessary to first learn various software applications. The current study employed the User Action Notation (UAN), a task-oriented notation that describes the behavior of the user and the interface during their cooperative performance of a task, to decompose complex tasks into primitive components. A set of primitive cursor actions was developed which contains the elementary cursor actions found in complex tasks. A graphics software application was then evaluated, using the UAN, with respect to the frequency of occurrence of each of the primitive user-cursor actions. Individual's ability to perform each primitive user-cursor action with three different input devices was then be measured. These measures were used to form estimates of the individual's ability to perform the graphics task with each input device. Correlations between predicted performance and measured performance on the graphics task were found to exceed 0.9. Results demonstrate the success of the method described herein for predicting complex task performance based on simple task performance, as well as, the usefulness of the UAN for decomposing complex tasks into primitive components.

Automated Computer-Aided Layout Planning for Robot Workcells

Abstract This text presents an approach for planning robot workcells in three dimensions fully automatically. This automation is possible by a complete layout planning process inside the configuration space. To reach a sufficient shop floor layout in a short time, the cartesian configuration space and fast obstacle transformation routines are employed. An optimization algorithm minimizes the length of all collision free paths required for the performance of the workcell task. A final check by a graphical workcell task simulation, whether the layout is valid or not, is no longer required. This new planning approach enhances the conventional layout planning process and reduces the amount of necessary user interaction.

Manpower, Personnel, Training and Safety (MPTS) Simulation Tools: Network and Simulation for Workload Assessment and Modeling (SIMWAM)

MANPRINT simulations in the early stages of weapon system acquisition involve modeling of functional and task sequences for individual operators/maintainers and for crews. The models identify function and task sequences associated with alternate function allocation approaches and design concepts. One tool developed for the task modeling activity is NETWORK™, a graphic task sequencing tool which establishes the predecessor relationships among tasks and supports the identification of the complete set of tasks. In the assessment of the adequacy of alternate function allocation strategies of roles-of-man vs automation, task sequences are modeled to reflect the distinguishing characteristics of each allocation approach. The allocation concepts and/or design concepts are then evaluated through the use of SIMWAM™ (Simulation for Workload Assessment and Modeling) workload assessment modeling procedure. With SIMWAM the workloads and performance problems for each alternate allocation approach can be determined, and multi-operator workloads can be quantified. During a SIMWAM run, tasks are called when prior tasks are completed. If sufficient operators are available for a called task, then it will be started. Input data which describe a task include a list of qualified operators and the number of these required to perform the task. In attempting to start a task, SIMWAM will assign qualified operators who are currently idle. SIMWAM can also interrupt lower priority tasks in process to obtain operators for higher priority tasks. This paper describes the NETWORK and SIMWAM tools and presents reports of the results of specific applications of the the two tools.

Two individual computer workstations

This article describes two workstations to operate at under $10,000 and designed to provide the computer capabilities for a number of art- and design-related tasks. The article questions whether one computer graphic system and workstation is really suitable for all computer graphic tasks at least at the low and middle ranges of computer equipment and software. † † One computer workstation was provided by the Computer Science Center of the University of Maryland, College Park Campus in June of 1989 as a part of a special faculty workstation program which has been conducted at the University over the past year. Implications for education in the arts are discussed and a range of options for the artist as well as the art educator are presented. Practical options and concerns for the purchase of computer hardware and software and video-related equipment are also discussed.

Comparative analysis of actual and mental movement times in two graphic tasks

This study compared the temporal organization of graphic movements executed either actually or mentally. Six subjects had to perform two tasks, writing a sentence and drawing a cube, either as a real performance or as an imagined one, with either the right or the left hand, and with either a small or a large tracing amplitude. In the same subject, for the same hand, mental and actual movement times were both very stable and very close from trial to trial regardless of the tracing amplitude. Thus, mental movements mimic closely real movements in their temporal organization and are likely to involve the same planning program.

RCBF landscapes during motor performance and motor ideation of a graphic gesture.

The regional cerebral blood flow (rCBF) distribution was measured by 133xenon inhalation using a gamma camera in 18 right-handed volunteers, 6 subjects performing a graphic task (writing numbers in letters) with the right hand, 6 subjects imagining the same task, and 6 subjects were assessed during two rest periods to determine the reproducibility of the technique. The mean rCBF increased between 10% and 25% (P less than 0.01) during both motor performance and motor ideation. However, there were regional differences. While motor performance activated mainly the rolandic regions bilaterally, motor ideation gave prefrontal and premotor rCBF augmentations. In both situations there was significant bilateral increase in regions corresponding to the cerebellum.