An evaluation of physics engines and their application in haptic virtual assembly environments

Virtual Reality (VR) applications are employed in engineering situation to simulate real and artificial situations where the user can interact with 3D models in real time. Within these applications the virtual environment must emulate real world physics such that the system behaviour and interaction are as natural as possible and to support realistic manufacturing applications. As a consequence of this focus, several simulation engines have been developed for various digital applications, including VR, to compute the physical response and body dynamics of objects. However, the performance of these physics engines within haptic-enabled VR applications varies considerably. In this study two third party physics engines - Bullet and PhysXtm- are evaluated to establish their appropriateness for haptic virtual assembly applications. With this objective in mind five assembly tasks were created with increasing assembly and geometry complexity. Each of these was carried out using the two different physics engines which had been implemented in a haptic-enabled virtual assembly platform specifically developed for this purpose. Several physics-performance parameters were also defined to aid the comparison. This approach and the subsequent results successfully demonstrated the key strengths, limitations, and weaknesses of the physics engines in haptic virtual assembly environments

Simple dynamic model realization based on ODE

Cílem práce je návrh a realizace modelu dynamické soustavy pomocí knihovny Open Dynamic Engine a v dalším simulačním prostředí. Po provedení praktických experimentů sestavit množinu testovacích dat. Porovnat výsledky experimentů a zhodnotit vlastnosti ODE.The aim of presented work is the design and realization of a model of dynamic system with the usage of Open Dynamic Engine library with comparison to another simulation tool. The set of experimental data was created after practical experiments. Finally, the ODE analysis was made.

A new methodology to evaluate the performance of physics simulation engines in haptic virtual assembly

Purpose – In this study, a new methodology to evaluate the performance of physics simulation engines (PSEs) when used in haptic virtual assembly applications is proposed. This methodology can be used to assess the performance of any physics engine. To prove the feasibility of the proposed methodology, two-third party PSEs – Bullet and PhysXtm – were evaluated. The paper aims to discuss these issues. Design/methodology/approach – Eight assembly tests comprising variable geometric and dynamic complexity were conducted. The strengths and weaknesses of each simulation engine for haptic virtual assembly were identified by measuring different parameters such as task completion time, influence of weight perception and force feedback. Findings – The proposed tests have led to the development of a standard methodology by which physics engines can be compared and evaluated. The results have shown that when the assembly comprises complex shapes, Bullet has better performance than PhysX. It was also observed that the assembly time is directly affected by the weight of virtual objects. Research limitations/implications – A more comprehensive study must be carried out in order to evaluate and compare the performance of more PSEs. The influence of collision shape representation algorithms on the performance of haptic assembly must be considered in future analysis. Originality/value – The performance of PSEs in haptic-enabled VR applications had been remained as an unknown issue. The main parameters of physics engines that affect the haptic virtual assembly process have been identified. All the tests performed in this study were carried out with the haptic rendering loop active and the objects manipulated through the haptic device.CONACYT (National Science and Technology Council of Mexico) research grant CB-2010-01-154430 and EPSRC/IMRC grants 113946 and 11243

Création automatique des animations 3D

RÉSUMÉ La production traditionnelle d'animations 3D pour un jeu vidéo ou un film d'animation est un processus lourd. Les animateurs ont besoin de plusieurs années de pratique et de bons logiciels de création de contenu numérique pour réussir à créer des animations 3D. Cela est dû à la complexité du logiciel et à la complexité de la tâche. La création d'un cycle de marche réaliste dans une scène complexe nécessite de nombreux détails de bas niveau pour atteindre un niveau élevé de réalisme. Ce mémoire propose une vue de haut niveau dans la création automatique des animations 3D afin de simplifier le processus global de production de l'animation. Afin d'aborder cette problématique, l'objectif général de la recherche a consisté à élaborer un prototype logiciel capable de générer automatiquement des animations 3D qui représentent le sens d'une phrase simple. Ce projet faisait partie intégrale du projet GITAN dans le domaine de l'infographie. GITAN proposait une solution pour générer des animations 3D à partir du texte. La solution proposée dans ce mémoire constitue principalement le module graphique qui génère la scène 3D animée qui représente la phrase d'entrée. Avec ce système, la complexité de la construction de la scène animée est considérablement réduite, puisque nous utilisons une représentation textuelle pour décrire l'animation et les différents objets dans la scène. La revue bibliographique a suggéré que les systèmes semblables qui permettent de générer automatiquement des animations 3D à partir du texte sont souvent très orientés vers un domaine d'application spécifique, par exemple les accidents automobiles, les comportements ou les interactions des personnages. L'automatisation de la génération de la scène sur ces systèmes se base souvent sur des langages script ou des formalismes qui étaient souvent orientés au domaine d'application. De plus, nous voulions générer l'animation en utilisant un format d'échange 3D à la place d'afficher directement l'animation. Nous pensons que l'utilisation d'un format d'échange 3D nous permet de bien générer la scène 3D, puisqu'un bon format d'échange intermédiaire permet de bien définir une animation de façon standard et fournit des outils nécessaires pour son utilisation. Pour cette raison, nous avons utilisé COLLADA comme format 3D pour représenter nos animations. D'après ces observations, nous avons émis trois hypothèses de recherche. La première supposait qu'il était possible de créer un formalisme capable de décrire une scène animée à partir d'une phrase simple. Le formalisme nous permet de faire une description de la scène animée en utilisant des noeuds,des contraintes et des images clés. La deuxième hypothèse supposait qu'il est possible de traduire le script qui décrit la scène vers le fichier COLLADA. Nous avons proposé un système logiciel qui permet de traduire le script vers un fichier COLLADA qui contient l'animation 3D. Finalement, la troisième hypothèse supposait que l'animation générée par le système permet de communiquer le sens de la phrase initiale. Le système doit pouvoir communiquer le message de la phrase qui décrit la scène vers les observateurs. Pour tester ces hypothèses, la méthodologie que nous avons retenue consiste, premièrement, à la création du formalisme qui permet de décrire la scène 3D. Nous avons proposé un schéma XML qui permet de déclarer des noeuds, des animations prédéfinies, des contraintes et des images clés qui décrivent la scène la générer. Par la suite, nous avons proposé une architecture logicielle modulaire qui traduit le script vers le fichier COLLADA. Le système utilise des algorithmes pour positionner correctement les objets dans la scène et pour synchroniser les animations. Finalement, nous avons effectué un sondage pour valider la communication du message par les scènes 3D générées. Le résultat du sondage nous permet d'analyser la compréhension du message par les observateurs et l'influence de l'environnement de la scène 3D sur le message, et ainsi, déterminer s'il est possible de transmettre le sens de la phrase initiale avec l'animation 3D. Les résultats que nous avons obtenus sont très satisfaisants. Nous avons été capables de décrire les scènes avec le formalisme proposée. De plus, le système logiciel génère des fichiers COLLADA bien structurés et il est capable de générer deux types de scènes : des scènes statiques et des scènes animées. Finalement, l'analyse des résultats du sondage montre que les scènes animées permettent de mieux communiquer les messages que les scènes statiques, mais l'utilisation correcte de deux types de scènes en fonction de la phrase permet de bien communiquer le message. En eet, les phrases qui contiennent des verbes d'état seront mieux représentées par des scènes statiques, tandis que des animations 3D permettent de mieux représenter des phrases qui contiennent des verbes d'action. De plus, l'analyse de l'influence de l'environnement nous a permis de constater qu'il n'offre pas d'amélioration dans la communication du message. Ces résultats nous ont permis de constater que le système est capable de générer de façon automatique des animations 3D qui transmettent le sens d'une phrase simple ce qui permet de simplifier le processus de production traditionnelle des animations 3D.----------ABSTRACT The traditional production of 3D animations for a video game or an animated film is a cumbersome process. Animators need several years of practice and excellent skills using Digital Content Creation (DCC) software to successfully create 3D animations. This is due to the complexity of the software and the complexity of the task. Creating a realistic walk cycle in a complex scene requires many low-level details for achieving a high level of realism. This thesis proposes a high-level view in the automatic creation of 3D animations to simplify the overall process of animation production. To address this problem, the overall objective of the research was to develop a software prototype able to automatically generate 3D animations that represent the meaning of a simple sentence. This project was an integral part of the project GITAN in computer graphics. GITAN proposed a solution to generate 3D animations from text. The solution proposed in this paper is mainly the graphics module that generates animated 3D scene representing the input sentence. With this system, the complexity of building the animated scene is greatly reduced, since we use a textual representation to describe the animation and the various objects in the scene. The literature review suggested that similar systems that automatically generate 3D animations from text are often related to a specific application domain such as automobile accidents, behavior or interactions of the characters. The automation of the scene generation for these systems is often based on scripting languages related to an application domain. In addition, we wanted to generate the animation using a 3D exchange format instead of directly display the animation. We believe that using a 3D exchange format allows us to better generate the 3D scene, since a good intermediate exchange format allows to define animations as building blocks and provides the tools to use them. For this reason, we used COLLADA as 3D format to represent our animations. From these observations, we formulated three research hypotheses. The first one assumed that it was possible to create a formalism able to describe an animated scene from a simple sentence. The formalism allows us to make an animated description of the scene using nodes, constraints and keyframes. The second hypothesis assumed that it is possible to translate the script that described the scene to a COLLADA file. We proposed a software system that translates the script to a COLLADA file that contains the 3D animation. Finally, the third hypothesis assumed that the animation generated by the system communicate the original meaning of the sentence. The system must be able to communicate the message of the sentence describing the scene to the observers. To test these hypotheses, the methodology we have adopted consists, rst of all, in the creation of the formalism for describing the 3D scene. We have proposed an XML schema for declaring nodes, animation presets, constraints and keyframes to describe the scene. Subsequently, we proposed a modular software architecture that translates the script into the COLLADA file. The system uses algorithms to correctly position the objects in the scene and to synchronize animations. Finally, we conducted a survey to validate the communication of the message contained in the 3D scenes. The result of the survey allows us to analyze the transmission of the message to the observers and the influence of the environment of the 3D scene on the message, and so, determine if it's possible to transmit the original meaning of the sentence with the 3D animation. The results we obtained are very rewarding. We were able to describe the scenes with the proposed script language. In addition, the software system is generating well structured COLLADA files and it is capable of generating two types of scenes: static scenes and animated scenes. Finally, analysis of survey results shows that the animated scenes can better communicate messages than static scenes, but the proper use of the two types of scenes according to the phrase can eectively communicate the message. Indeed, sentences that contain state verbs will be better represented by static scenes, while 3D animations can more adequately represent sentences that contain action verbs. Furthermore, in the analysis of the influence of the environment, we found that it offers no improvement in communicating the message. These results revealed that the system is able to automatically generate 3D animations that convey the sense of a simple sentence to simplify the production process of traditional animation

A framework for the visualisation and control of ubiquitous devices, services and digital content

The General Organization for Technical Education and Vocational Training, Riyadh, Saudi Arabia, has developed a special feeding program for the students at its institutions. The effects of this program on the nutritional and health status of these students have not been evaluated yet, and since no published dietary research has been performed on Technical and Vocational young adult male students, the present work was undertaken to investigate the nutritional status of this community in Riyadh, Kingdom of Saudi Arabia. After a pilot survey, it was decided to use a selfcompleted questionnaire combined with personal interview to investigate the nutritional status of 690 students randomly selected from the study population. Dietary data was collected by two methods: usual weekly intakes "diet history" and actual daily intakes "diet diary". The nutrient intakes were calculated using the unilever Dietary Analysis Program (UNIDAP). The statistical Package for the social Science (SPSS/PC+) was employed to analyse the data; statistical significance of relationships between certain sets of data was determined by chi-square analysis. Some general factors affecting the nutritional status of these students were identified, their nutritional habits and attitudes were investigated, and the average daily intakes of energy, the macronutrients, and selected micronutrients were calculated. The main results of this study shows that the majority of the study population are adolescent, moderately active individuals, and have lower than the standard range of the Body Mass Index; anaemia is the most stated health problem; meal-skipping and eating between meals are common habits amongst the students. Regarding nutrient intake, there was an energy, polyunsaturated fat, and vitamin C deficiency; adequate intake of saturated fat, dietary fibre, retinol, and zinc; more than adequate intake of protein, total fat, cholesterol, thiamin, riboflavin, calcium, and iron. Recommendations are given which aim to improve the nutrition of technical and vocational students