Designing 3D Selection Techniques Using Ballistic and Corrective Movements

The two-component model is a human movement model in which an aimed movement is broken into a voluntary ballistic movement followed by a corrective movement. Recently, experimental evidence has shown that 3D aimed movements in virtual environments can be modeled using the two-component model. In this paper, we use the two-component model for designing 3D interaction techniques which aim at facilitating pointing tasks in virtual reality. This is achieved by parsing the 3D aimed movement in real time into the ballistic and corrective phases, and reducing the index of difficulty of the task during the corrective phase. We implemented two pointing techniques. The ‘AutoWidth’ technique increases the target width during the corrective phase and the ‘AutoDistance’ technique decreases the distance to the target at the end of ballistic phase. We experimentally demonstrated the benefit of these techniques by comparing them with freehand aimed movements. It was shown that both ‘AutoWidth’ and ‘AutoDistance’ techniques exhibit significant improvement on target acquisition time

The effect of varying path properties in path steering tasks

Path steering is a primitive 3D interaction task that requires the user to navigate through a path of a given length and width. In a previous paper, we have conducted controlled experiments in which users operated a pen input device to steer a cursor through a 3D path subject to fixed path properties, such as path length, width, curvature and orientation. From the experimental data we have derived a model which describes the efficiency of the task. In this paper, we focus on studying the movement velocity of 3D manipulation path steering when one or more path properties vary during the task. We have performed a repeated measures design experiment of 8 scenarios, including a scenario in which all path properties were kept constant, 3 scenarios in which the path width, curvature and orientation varied, 3 scenarios of varying two path properties, and 1 scenario of varying all properties. The analysis of our experimental data indicates that a path of varying orientation or width results in a low average steering velocity. During a continuous steering, the joint where a change in path curvature or orientation takes place also significantly decreases the velocity. In addition, path width and curvature are highly-correlated to the average velocity of a segment, i.e. the wider a segment (or the smaller the path curvature), the larger the average steering velocity on that segment. The results of this work could serve as guidelines for designing higher level interaction techniques and better user interfaces for traditional HCI tasks, e.g. 2D or 3D nested-menu navigation

Modeling object pursuit for 3D interactive tasks in virtual reality

Models of interaction tasks are quantitative descriptions of relationships between human temporal performance and the spatial characteristics of the interactive tasks. Examples include Fitts' law for modeling the pointing task and Accot and Zhai's steering law for the path steering task, etc. Models can be used as guidelines to design efficient user interfaces and quantitatively evaluate interaction techniques and input devices. In this paper, we introduce a 3D object pursuit interaction task, in which users are required to continuously track a moving target in a virtual environment. The entire movement of the task is broken into a tracking phase and a correction phase. For each phase, we propose a model that has been verified by two experiments. As the experimental results show, the time for the tracking phase is fixed once a task has been established, while the time for the correction phase usually varies according to some characteristics of the task. It can be modeled as a function of path length, target width and the velocity with which the target moves. The proposed model can be used to quantitatively evaluate the efficiency of user interfaces that involve the interaction with moving objects

Baggeren in de Loosdrechtse Plassen : een verslag van een studiedag van de Werkgroep Waterkwaliteits Onderzoek Loosdrechtse Plassen over de baggerproblematiek in de Loosdrechtse Plassen, Bilthoven, 16 oktober 1987

Het baggeren van sediment, als aanvullende maatregel ter bestrijding van eutrofiëring, is al enige tijd in discussie. Ook in de Loosdrechtse Plassen is de problematiek opportuun, daar sanering van het inlaatwater en huishoudelijk afvalwater niet direct heeft geleid tot een verbetering van de waterkwaliteit. De baggerproblematiek wordt aan de orde gesteld omdat er vanuit beleids- en beheerskringen bij voortduring wordt gevraagd om vertalingvan in de werkgroep vergaarde kennis naar de praktijk van beheer en beleid, en omdat concentratie op een bepaald probleem integrerend werken kan op de wetenschappelijke vraagstelling en toepassing van onderzoeksresultaten. De baggerproblematiek wordt benaderd vanuit natuurwetenschappelijk oogpunt, met nadruk op de milieubelangen

Comparing Aimed Movements in the Real World and in Virtual Reality

The study of aimed movements has a long history, starting at least as far back as 1899 when Woodworth proposed a two-component model in which aimed movements are broken into an initial ballistic phase and an additional control phase. In this paper, we use Woodworth’s model for experimentally comparing aimed movements in the real world with those in a virtual environment. Trajectories from real world movements have been collected and compared to trajectories of movements taken from a virtual environment. From this, we show that significant temporal differences arise in both the ballistic and control phases, but the difference is much larger in the control phase; users’ improvement is relatively greater in the virtual world than in the real world. They progress more in ballistic phase in the real world, but more in correction phase in the virtual world. These results allow us to better understand the pointing tasks in virtual environments

Comparing Aimed Movements in the Real World and in Virtual Reality

The study of aimed movements has a long history, starting at least as far back as 1899 when Woodworth proposed a two-component model in which aimed movements are broken into an initial ballistic phase and an additional control phase. In this paper, we use Woodworth’s model for experimentally comparing aimed movements in the real world with those in a virtual environment. Trajectories from real world movements have been collected and compared to trajectories of movements taken from a virtual environment. From this, we show that significant temporal differences arise in both the ballistic and control phases, but the difference is much larger in the control phase; users’ improvement is relatively greater in the virtual world than in the real world. They progress more in ballistic phase in the real world, but more in correction phase in the virtual world. These results allow us to better understand the pointing tasks in virtual environments

Revealing the secrets of Chinese ivory puzzle balls: Quantifying the crafting process using X-ray Computed Tomography

Chinese ivory puzzle balls are known for their beauty, finesse and their ability to intrigue viewers. From the eighteenth century until recently, they have been crafted by turning, using a simple lathe and a set of drilling and carving tools developed in the eighteenth century. The craft of Chinese ivory puzzle balls has been described as the ‘devil’s work’, as it requires a great deal of proficiency, accuracy and patience.This study presents a novel method for quantifying the crafting process of Chinese ivory puzzle balls. The method is based on measuring the morphological properties of ivory balls in three-dimensional images obtained using X-ray Com-puted Tomography (ct) scanning techniques. The accuracy of the crafting process is obtained by comparing the measured properties with an underlying mathematical model of the ball. We apply the proposed method to ivory balls from the Rijks-museum in Amsterdam and the National Palace Museum in Taipei. The results show substantial differences in the accuracy of the crafting process.From an art-historical perspective, the results show that the accuracy of the crafting process evolved during the eighteenth century. They also suggest that the ivory balls we have analyzed have been crafted with different types of turning tools.</p

Trauma, Memory and Religion

How can we screen trauma? This question might lead the perception of documentary films about atrocities in the 20th and 21st centuries, like S21 THE KHMER ROUGE KILLING MACHINE (Rithy Panh, CAMB/FR 2003) about Cambodia, THE LOOK OF SILENCE (Joshua Oppenheimer, ID/DK 2014) about Indonesia or DAS RADIKAL BÖSE (Stefan Ruzowitzky, AT 2013) about Nazi-Europe. A concern that may emerge as we watch films on atrocities is whether these artistic representations perhaps guide the public away from what “really happened”. There certainly is a huge gap between, on the one hand, the immediate experience of the event that lies behind the interpretative screening and, on the other hand, watching the director’s material while neither being a part nor ever having been part of the event. Yet often filmic representations are not intended to show what happened; instead they present case studies to be explored in the present. Often the films contain an inherent critique of genocidal violence and present humanistic perspectives on obedience. Mostly, these films underline the humanity of the victims, seeking to give names, faces and biographies so that they are much more than just numbers. What appears on the screen therefore challenges the audience with a moral question: what would you do