Thesis (M.S.)--Brigham Young University. Dept. of Computer Science, 2007. / Includes bibliographical references (p. 59-61).

A etapa de broad-phase para a detecção de colisão em cenas compostas de n objetos que se movimentam é um problema desafiador, pois enumerar os pares de colisão revela uma complexidade quadrática. Estruturas de dados espaciais são desenvolvidas para acelerar o processo, mas muitas vezes a natureza estática dessas estruturas dificulta o manejo de cenas dinâmicas. Nesse trabalho, é proposta uma nova estrutura chamada de árvore BSP semi-ajustável para representar cenas compostas de milhares de objetos dinâmicos. Um algoritmo de agendamento avalia onde a árvore BSP torna-se desbalanceada, usa várias estratégias para alterar os planos de corte e atualizações preguiçosas para reduzir os custos de reconstrução. É mostrado que a árvore não precisa uma total reconstrução mesmo em cenas altamente dinâmicas, ajustando-se e mantendo propriedades desejáveis de balanceamento e profundidade. / The broad-phase step of collision detection in scenes composed of n moving objects is a challenging problem because enumerating collision pairs has an inherent O(n²) complexity. Spatial data structures are designed to accelerate this process, but often their static nature makes it difficult to handle dynamic scenes. In this work we propose a new structure called Semi-Adjusting BSP-tree for representing scenes composed of thousands of moving objects. A scheduling algorithm evaluates locations where the BSP-tree becomes unbalanced, uses several strategies to alter cutting planes, and defers updates based on their re-structuring cost. We show that the tree does not require a complete re-structuring even in highly dynamic scenes, but adjusts itself while maintaining desirable balancing and height properties.

A etapa de broad-phase para a detecção de colisão em cenas compostas de n objetos que se movimentam é um problema desafiador, pois enumerar os pares de colisão revela uma complexidade quadrática. Estruturas de dados espaciais são desenvolvidas para acelerar o processo, mas muitas vezes a natureza estática dessas estruturas dificulta o manejo de cenas dinâmicas. Nesse trabalho, é proposta uma nova estrutura chamada de árvore BSP semi-ajustável para representar cenas compostas de milhares de objetos dinâmicos. Um algoritmo de agendamento avalia onde a árvore BSP torna-se desbalanceada, usa várias estratégias para alterar os planos de corte e atualizações preguiçosas para reduzir os custos de reconstrução. É mostrado que a árvore não precisa uma total reconstrução mesmo em cenas altamente dinâmicas, ajustando-se e mantendo propriedades desejáveis de balanceamento e profundidade. / The broad-phase step of collision detection in scenes composed of n moving objects is a challenging problem because enumerating collision pairs has an inherent O(n²) complexity. Spatial data structures are designed to accelerate this process, but often their static nature makes it difficult to handle dynamic scenes. In this work we propose a new structure called Semi-Adjusting BSP-tree for representing scenes composed of thousands of moving objects. A scheduling algorithm evaluates locations where the BSP-tree becomes unbalanced, uses several strategies to alter cutting planes, and defers updates based on their re-structuring cost. We show that the tree does not require a complete re-structuring even in highly dynamic scenes, but adjusts itself while maintaining desirable balancing and height properties.

A etapa de broad-phase para a detecção de colisão em cenas compostas de n objetos que se movimentam é um problema desafiador, pois enumerar os pares de colisão revela uma complexidade quadrática. Estruturas de dados espaciais são desenvolvidas para acelerar o processo, mas muitas vezes a natureza estática dessas estruturas dificulta o manejo de cenas dinâmicas. Nesse trabalho, é proposta uma nova estrutura chamada de árvore BSP semi-ajustável para representar cenas compostas de milhares de objetos dinâmicos. Um algoritmo de agendamento avalia onde a árvore BSP torna-se desbalanceada, usa várias estratégias para alterar os planos de corte e atualizações preguiçosas para reduzir os custos de reconstrução. É mostrado que a árvore não precisa uma total reconstrução mesmo em cenas altamente dinâmicas, ajustando-se e mantendo propriedades desejáveis de balanceamento e profundidade. / The broad-phase step of collision detection in scenes composed of n moving objects is a challenging problem because enumerating collision pairs has an inherent O(n²) complexity. Spatial data structures are designed to accelerate this process, but often their static nature makes it difficult to handle dynamic scenes. In this work we propose a new structure called Semi-Adjusting BSP-tree for representing scenes composed of thousands of moving objects. A scheduling algorithm evaluates locations where the BSP-tree becomes unbalanced, uses several strategies to alter cutting planes, and defers updates based on their re-structuring cost. We show that the tree does not require a complete re-structuring even in highly dynamic scenes, but adjusts itself while maintaining desirable balancing and height properties.

Intersections tests between meshes in physics engines are time consuming and computationalheavy tasks. In order to speed up these intersection tests, each mesh can be decomposedinto several smaller convex hulls where the intersection test between each pair of these smallerhulls becomes more computationally efficient. The decomposition of meshes within the game industry is today performed by digital artistsand is considered a boring and time consuming task. Hence, the focus of this master thesislies in automatically decompose a mesh into several smaller convex hulls and to approximatethese decomposed pieces with bounding volumes of different complexity. These boundingvolumes together represents a collision mesh that is fully usable in modern games.

A proposta deste trabalho é demonstrar a viabilidade de um sistema para inserção de um vídeo-avatar interativo em um ambiente virtual 3D, utilizando-se somente um computador pessoal e câmeras domésticas. Sua contribuição, em relação a trabalhos similares, consiste em integrar técnicas e algoritmos em uma solução inovadora de baixo custo computacional, voltada principalmente para aplicações de educação e entretenimento. Este trabalho expande as pesquisas realizadas anteriormente no Laboratório de Tecnologias Interativas sobre vídeo-avatares para teleconferência. O vídeo-avatar proposto é posicionado corretamente em relação a outros objetos do ambiente virtual e pode interagir com eles, sem a utilização de técnicas de reconstrução geométrica que apresentam altos custos de processamento. A demonstração da viabilidade da proposta é feita através da implementação de protótipos. / The proposal of this work is to demonstrate the feasibility of a system for the insertion of an interactive video avatar in a 3D virtual environment, using a single personal computer and home-use cameras. Its contribution, relative to similar works, consists in integrating techniques and algorithms in an innovative solution with low computational cost, aimed mainly at educational and entertainment applications. This work extends research previously performed at the Laboratório de Tecnologias Interativas about video avatars for teleconferencing. The proposed video avatar is correctly positioned in relation to other objects in the virtual environment and is capable of interacting with them, without resorting to geometric reconstruction techniques that present high processing costs. The demonstration of the feasibility of the proposal is performed through the implementation of prototypes.

<p>This paper describes our game engine written in C++, using the DirectX libraries for graphics, sound and input. Since the engine is written using DirectX, an introduction to this system is given. The report gives a description of the structure of the game and the game kernel. Following this is a description of the graphics engine and its core components. The main focus of the engine is on the physics and how it is used in the game to simulate reality. Input is discussed briefly, with examples to show how it relates to the physics engine. Implementation of audio in the game engine is not described, but a general description of how sound is used in games is given. A theory for the basics of how artificial intelligence can be used in the engine is presented. The system for the architecture of the levels is described as is its connection to the graphics engine. The last section of the report is an evaluation and suggestions for what to do in the future. A user manual for the level editor is included as an appendix.</p>

Human-robot interaction (HRI) is the future of robotics. It is essential in the expanding markets, such as surgical, medical, and therapy robots. However, existing industrial systems can also benefit from safe and effective HRI. Many robots are now being fitted with joint torque sensors to enable effective human-robot collision detection. Many existing and off-the-shelf industrial robotic systems are not equipped with these sensors. This work presents and demonstrates a method for effective collision detection on a system with motor current feedback instead of joint torque sensors. The effectiveness of this system is also evaluated by simulating collisions with human hands and arms. Joint torques are estimated from the input motor currents. The joint friction and hysteresis losses are estimated for each joint of an SIA5D 7 Degree of Freedom (DOF) manipulator. The estimated joint torques are validated by comparing to joint torques predicted by the recursive application of Newton-Euler equations. During a pick and place motion, the estimation error in joint 2 is less than 10 Newton meters. Acceleration increased the estimation uncertainty resulting in estimation errors of 20 Newton meters over the entire workspace. When the manipulator makes contact with the environment or a human, the same technique can be used to estimate contact torques from motor current. Current-estimated contact torque is validated against the calculated torque due to a measured force. The error in contact force is less than 10 Newtons. Collision detection is demonstrated on the SIA5D using estimated joint torques. The effectiveness of the collision detection is explored through simulated collisions with the human hands and arms. Simulated collisions are performed both for a typical pick and place motion as well as trajectories that transverse the entire workspace. The simulated forces and pressures are compared to acceptable maximums for human hands and arms. During pick and place motions with vertical and lateral end effector motions at 10mm/s and 25mm/s, the maximum forces and pressures remained below acceptable levels. At and near singular configurations some collisions can be difficult to detect. Fortunately, these configurations are generally avoided for kinematic reasons. / text

Crowd simulations are attracting increasing attention from both academia and the industry field and are implemented across a vast range of applications, from scientific demonstrations to video games and films. As such, the demand for greater realism in their aesthetics and the amount of agents involved is always growing. A successful crowd simulation must simulate large numbers of pedestrians' behaviours as realistically as possible in real-time. The thesis looks at two important aspects of crowd simulation and real-time animation. First, this thesis introduces a new data structure called Extended Oriented Bounding Box (EOBB) and related methods for fast collision detection and obstacle avoidance in the simulation of crowd motion in virtual environments. The EOBB is extended to contain a region whose size is defined based on the instantaneous velocity vector, thus allowing a bounding volume representation of both geometry and motion. Such a representation is also found to be highly effective in motion planning using the location of vertices of bounding boxes in the immediate neighbourhood of the current crowd member. Second, we present a detailed analysis of the effectiveness of spatial subdivision data structures, specifically for large-scale crowd simulation. For large-scale crowd simulation, computational time for collision detection is huge, and many studies use spatial partitioning data structure to reduce the computational time, depicting their strengths and weaknesses, but few compare multiple methods in an effort to present the best solution. This thesis attempts to address this by implementing and comparing four popular spatial partitioning data structures with the EOBB.

How much damage can a malicious tiny device cause in a single-hopwireless network? Imagine two players, Alice and Bob, who want toexchange information. Collin, a malicious adversary, wants to preventthem from communicating. By broadcasting at the same time as Alice orBob, Collin can destroy their messages or overwhelm them with his ownmalicious data. Being a tiny device, however, Collin can onlybroadcast up to B times. Given that Alice and Bob do not knowB, and cannot distinguish honest from malicious messages, howlong can Collin prevent them from communicating? We show the answerto be 2B + Theta(lg|V|) communication rounds, where V is theset of values that Alice and Bob may transmit. We prove this resultto be optimal by deriving an algorithm that matches our lowerbound---even in the stronger case where Alice and Bob do not start thegame at the same time.We then argue that this specific 3-player game captures the generalextent to which a malicious adversary can disrupt coordination in asingle-hop wireless network. We support this claim by deriving---via reduction from the 3-player game---round complexity lower boundsfor several classical n-player problems: 2B + Theta(lg|V|) for reliable broadcast,2B + Omega(lg(n/k)) for leader election among k contenders,and 2B + Omega(k*lg(|V|/k)) for static k-selection. We then consider an extension of our adversary model that also includes up to t crash failures. We study binary consensus as the archetypal problem for this environment and show a bound of 2B + Theta(t) rounds. We conclude by providing tight, or nearly tight, upper bounds for all four problems. The new upper and lower bounds in this paper represent the first such results for a wireless network in which the adversary has the ability to disrupt communication.