Incorporating constraints into a Virtual Reality environment for intuitive and precise solid modelling

The absence of constraints when interacting with virtual objects is one of the major limitations in the current Virtual Reality (VR) environments. Without constraints, it is difficult to perform precise interactive manipulations and precise solid modelling in VR environments cannot be ensured. In this paper, constraint-based 3D direct manipulations are acquired through incorporating constraints into the VR environment for intuitive and precise solid modelling. Solid modelling in the VR environment is precisely performed in an intuitive manner through precise constraint-based manipulations. Constraint-based manipulations are accompanied by automatic constraint recognition and precise constraint satisfaction and are realized by allowable motions for precise 3D interactions in the VR environment. The allowable motions are represented as a mathematical matrix for conveniently deriving the allowable motions from constraints. A procedure-based degree-of-freedom incorporation approach for 3D constraint solving is presented to derive the allowable motions. A rule-based constraint recognition engine is developed for both constraint-based manipulations and implicitly incorporating constraints into the VR environment. Some special constraint-based manipulations are also implemented as modelling operations for solid modelling in the VR environment.

The absence of efficient constraint management facilities when interacting with virtual objects is one of the major limitations of current virtual reality (VR) systems for CAD applications. Without constraint management facilities, it is difficult to perform precise interactions with today's 3D input devices and precise solid modeling in the VR environments cannot be ensured. In this paper, a constraint manager is presented for intuitive and precise solid modeling in the VR environment. This constraint manager generates constraint-based 3D direct manipulations for precise solid modeling through incorporating constraints into the VR environment. Constraint-based manipulations are realized by allowable motions for precise 3D interactions in the VR environment. The allowable motions are represented as a mathematical matrix for conveniently deriving allowable motions from constraints. A procedure-based degree-of-freedom incorporation solver for solving 3D constraints is presented for deriving the allowable motions. A rule-based constraint recognition engine is developed for implicitly incorporating constraints into the VR environment.© (2003) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Virtual Reality (VR) technology is a natural extension of 3D computer graphics with advanced input and output devices and brings a completely new environment to the CAD community. However, with today’s VR systems, it is difficult to directly and precisely create and modify objects in a VR environment. This paper presents an efficient approach for solid modelling in a VR environment. Solid modelling in the VR environment is precisely performed in an intuitive manner through precise constraint-based manipulations. Constraint-based manipulations are accompanied with automatic constraint recognition and precise constraint satisfaction for establishing the hierarchically structured constraint-based data model and are realized by allowable motions for precise 3D interactions in the VR environment. The allowable motions are represented as a mathematical matrix for conveniently deriving the allowable motions from constraints. A procedure-based degree-of-freedom incorporation method for 3D constraint solving is presented for deriving the allowable motions. A rule-based constraint recognition engine is developed for automatic constraint recognition. A prototype system has been developed for solid modelling in the VR environment, where the user can create solid models in an intuitive manner through precise constraint-based manipulations.

With today's virtual reality (VR) systems, it is difficult to create precise assembly models through 3D interactions due to hardware limitations. In this paper, an efficient approach is presented for intuitive and precise assembly modeling in a VR environment. Assembly modelling is performed by precise constraint-based 3D direct manipulations in an intuitive manner. Constraint-based manipulations are accompanied with automatic constraint recognition and precise constraint satisfaction, and are realized by allowable motions for precise 3D interactions in the VR environment. Some special constraint-based assembly operations are constructed for assembly modelling in the VR environment. A method for recognizing the pairs of mating features between assembly components is presented. This method integrates 3D direct manipulations with a feature mating knowledge base and makes the process of recognizing a pair of mating features intuitive. A concept of offset solid is also presented for determining assembly components. A prototype system has been developed for assembly modelling through precise constraint-based manipulations in an intuitive manner in the VR environment.

With today’s virtual reality (VR) systems, it is difficult to directly and precisely create and modify objects in a VR environment. This chapter presents an approach for solid modelling in a VR environment. Solid modelling in the VR environment is performed precisely in an intuitive manner through constraint-based manipulations. A hierarchically structured and constraint-based data model is developed to support solid modelling in the VR environment. The data model integrates a high-level constraint-based model for precise object definition, a mid-level constructive solid geometry/boundary representation (CSG/BRep) hybrid solid model for hierarchical geometry abstractions and object creation, and a low-level polygon model for real-time visualization and interaction in the VR environment. Constraints are embedded in the solid model and are organized at different levels to reflect the modelling process from features to parts. Constraint-based manipulations are accompanied with automatic constraint recognition and precise constraint satisfaction to establish the hierarchically structured constraint-based data model and are realized by allowable motions for precise 3D interactions in the VR environment. The allowable motions are represented as a mathematical matrix for conveniently deriving allowable motions from constraints. A procedure-based degree-of-freedom (DOF) combination approach for 3D constraint solving is presented for deriving the allowable motions.

A methodology for solid modelling in a virtual reality environment

A hierarchically structured and constraint-based data model for intuitive and precise solid modeling in a virtual reality environment

This paper presents a constraint-based methodology for intuitive and precise solid modelling in a virtual reality (VR) environment. A hierarchically structured and constraint-based data model is developed to support solid modelling in the VR environment. A constraint reasoning engine is also developed to automatically deduce allowable motions for precise constraint-based 3D manipulations. A prototype system of product modelling has been successfully developed, and experimental results demonstrate the advantage of precise solid modelling through constraint-based manipulation in virtual environments.

Background Freezing of gait (FoG) is a common target of rehabilitative interventions for people with Parkinson disease (PD). Virtual reality (VR) holds potential for advancing research and clinical management of FoG through flexible creation of FoG-provoking environments that are not easily or safely replicated in the clinic. Objective The aim of this study was to investigate whether VR environments that replicate FoG-provoking situations would exacerbate gait impairments associated with FoG compared to unobstructed VR and physical laboratory environments. Methods Gait characteristics (pace, rhythm, variability, asymmetry, and postural control domains) and festination were measured using motion capture while people with PD walked in VR environments based on FoG-provoking situations (doorway, hallway, and crowd environments) compared to unobstructed VR and physical laboratory environments. The effect of VR environments was assessed using one-way repeated measures ANOVAs with planned contrasts. Results Ten participants (mean age 74.1 years, 3 females, Hoehn and Yahr stage 2–3) with PD who self-reported FoG participated. Gait speed and step length were reduced in all VR environments compared to the physical laboratory. Step width was wider, step length was more variable, and festination was more common for some of the VR environments compared to the physical laboratory environment. Compared to the unobstructed virtual laboratory environment, step length was more variable in VR crowd and doorway environments. Conclusions The exacerbation of gait impairments that are characteristic precursors of FoG in FoG-provoking VR environments supports the potential utility of VR technology in the assessment and treatment of gait impairments in PD. Implications for rehabilitation Freezing increases fall risk and reduces quality of life in Parkinson disease (PD). Virtual reality (VR) can simulate visuospatial environments that provoke freezing. Immersive VR doorway, hallway, and crowd environments were developed. Gait speed slowed when people with PD walked overground in all VR environments. Step variability and festination increased in freeze-provoking environments.

Virtual reality (VR) provides a completely digital world of interaction which enables the users to modify, edit, and transform digital elements in a responsive way. Mixed reality (MR), which is the result of blending the digital world and the physical world together, brings new advancements and challenges to human, computer and environment interactions. This paper focuses on adapting the already-existing methods and tools in architecture to both VR and MR environments under sustainable architectural design domain. For this purpose, we benefit from the semantically enriched data platforms of Building information modelling (BIM) tools, the performance calculation functions of building energy simulation tools while transcending these data into VR and MR environments. In this way, we were able to merge these diverse data for the virtual design activity. Nine participants have already tested the initial prototype of MR-based only interaction environment in our previous study [1]. According to the feedbacks, the user interface and interaction mechanisms were updated and the environment was made accessible also in VR. These updates made four types of interactions possible in MR and VR: 1) MR environment using HoloLens with gestures, 2) MR environment using HoloLens with a clicker, 3) VR environment using HTC Vive with two controllers, and 4) HoloLens emulator with a mouse. All these interaction cases were tested by 21 architecture students in an in-house workshop. In this workshop, we collected data on presence, usability, and technology acceptance of these cases. Our results show that interaction in a VR environment is the most natural interaction type and the participants were eager to use both MR and VR environments instead of an emulator. To our best of knowledge, this is the first comparative study of a BIM-based architectural design medium in both VR and MR environments.

This paper presents a constraint-based methodology for product design with advanced virtual reality technologies. A hierarchically structured and constraint-based data model is developed to support product design from features to parts and further to assemblies in a VR environment. Product design in the VR environment is performed in an intuitive manner through precise constraint-based manipulations. Constraint-based manipulations are accompanied with automatic constraint recognition and precise constraint satisfaction to establish constraints between objects, and are further realized by allowable motions for precise 3D interactions in the VR environment. The allowable motions are represented as a mathematical matrix and derived from constraints between objects by constraint solving. A procedure-based degrees-of-freedom combination approach is presented for 3D constraint solving. A rule-based constraint recognition engine is developed for both constraint-based manipulations and implicitly incorporating constraints into the VR environment. An intuitive method is presented for recognizing pairs of mating features between assembly components. Examples are presented to demonstrate the efficacy of the proposed methodology.

The objective of this study was to construct systems for haptic virtual reality (VR) environment and to conduct an experiment to compare muscular activity during ball catching tasks in real and VR environments, where the level of the presence was evaluated. A ball catching task was demonstrated in two environments, where head-mounted display and SPIDAR-HS, the haptic presentation device using tensile force of the wire, were applied for constructing VR environment. As an index of dynamic muscular activity, forearm EMG signals were measured in the time course of a ball catching task. Average peak RMS value for forearm EMG in VR environment was 45.2% smaller than that in real environment. This difference was apparent because the amount of force generated by SPIDAR-HS was relatively lower than that made by the gravity force of the ball. On the other hand, the trends in dynamic muscular activities were similar for both environment, indicating that two tasks were fairly unique regardless the type of environments. It was concluded that the presence of VR was observable by the dynamic muscular changes during VR tasks with further adjustment of force levels required for the task in VR environment.

Spatiotemporal gait deviations in a virtual reality environment

ObjectiveEvaluation of the benefits of a virtual reality (VR) environment with a head-mounted display (HMD) for decision-making in liver surgery.BackgroundTraining in liver surgery involves appraising radiologic images and considering the patient’s clinical information. Accurate assessment of 2D-tomography images is complex and requires considerable experience, and often the images are divorced from the clinical information. We present a comprehensive and interactive tool for visualizing operation planning data in a VR environment using a head-mounted-display and compare it to 3D visualization and 2D-tomography.MethodsNinety medical students were randomized into three groups (1:1:1 ratio). All participants analyzed three liver surgery patient cases with increasing difficulty. The cases were analyzed using 2D-tomography data (group “2D”), a 3D visualization on a 2D display (group “3D”) or within a VR environment (group “VR”). The VR environment was displayed using the “Oculus Rift ™” HMD technology. Participants answered 11 questions on anatomy, tumor involvement and surgical decision-making and 18 evaluative questions (Likert scale).ResultsSum of correct answers were significantly higher in the 3D (7.1 ± 1.4, p < 0.001) and VR (7.1 ± 1.4, p < 0.001) groups than the 2D group (5.4 ± 1.4) while there was no difference between 3D and VR (p = 0.987). Times to answer in the 3D (6:44 ± 02:22 min, p < 0.001) and VR (6:24 ± 02:43 min, p < 0.001) groups were significantly faster than the 2D group (09:13 ± 03:10 min) while there was no difference between 3D and VR (p = 0.419). The VR environment was evaluated as most useful for identification of anatomic anomalies, risk and target structures and for the transfer of anatomical and pathological information to the intraoperative situation in the questionnaire.ConclusionsA VR environment with 3D visualization using a HMD is useful as a surgical training tool to accurately and quickly determine liver anatomy and tumor involvement in surgery.

BackgroundAdolescent mental health is a national mental health emergency amid surging rates of anxiety and depression. Given the scarcity and lack of scalable mental health services, the use of self-administered, evidence-based technologies to support adolescent mental health is both timely and imperative.ObjectiveThe goal of this study was 2-fold: (1) to determine the feasibility, usability, and engagement of a participatory designed, nature-based virtual reality (VR) environment and (2) to determine the preliminary outcomes of our self-administered VR environment on depression, mindfulness, perceived stress, and momentary stress and mood.MethodsWe conducted a within-person, 3-week, in-home study with a community-based sample of 44 adolescents. Participants completed surveys of perceived stress, depression, cognitive fusion, and mindfulness at intake, postintervention, and a 3-week follow-up. Participants were invited to use a nature-based, VR environment that included 6 evidence-based activities 3 to 5 times per week. They completed momentary stress and mood surveys 5 times each day and before and after each VR session. Postintervention, participants completed surveys on system and intervention usability and their experiences with using the VR system. Quantitative data were analyzed using descriptive statistics and mixed effects modeling to explore the effect of the VR environment on stress. Qualitative data were analyzed using collaborative thematic analysis.ResultsParticipants’ use of the VR environment ranged from 1 session to 24 sessions (mean 6.27 sessions) at home over a 3-week period. The 44 participants completed all study protocols, indicating our protocol was feasible and the VR environment was engaging for most. Both the use of the VR system and novel VR intervention received strong usability ratings (mean 74.87 on the System Usability Scale). Most teens indicated that they found the tool to be easily administered, relaxing, and helpful with stress. For some, it offered space to process difficult emotions. The themes calm, regulating, and forget about everything resulted from open-ended exit interview data. Although the Relaxation Environment for Stress in Teens (RESeT) did not significantly affect repeated survey measurements of depression, mindfulness, nor cognitive fusion, it did positively affect momentary mood (pre-intervention: 10.8, post-intervention: 12.0, P=.001) and decrease momentary stress (pre-intervention: 37.9, post-intervention: 20.6, P=.001). We found a significant reduction in within-day momentary stress that strengthened with increased VR use over time during the study period (P=.03).ConclusionsThese preliminary data inform our own VR environment design but also provide evidence of the potential for self-administered VR as a promising tool to support adolescent mental health. Self-administered VR for mental health may be an effective intervention for reducing adolescent stress. However, understanding barriers (including disengagement) to using VR, as well as further encouraging participatory design with teens, may be imperative to the success of future mental health interventions.