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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.

Collision detection for ellipsoids and other quadrics

Choi, Yi-king., 蔡綺瓊. January 2008 (has links)
The Best PhD Thesis in the Faculties of Dentistry, Engineering, Medicine and Science (University of Hong Kong), Li Ka Shing Prize,2007-2008 / published_or_final_version / Computer Science / Doctoral / Doctor of Philosophy

Collision detection for ellipsoids and other quadrics

Choi, Yi-king. January 2008 (has links)
Thesis (Ph. D.)--University of Hong Kong, 2008. / Includes bibliographical references (p. 133-141) Also available in print.

Sensory coding of complex visual motion in the locust (Locusta migratoria)

2013 September 1900 (has links)
The visual environment of any animal is a complex amalgamation of sensory information (Lochmann and Deneve, 2011); however, it is adaptive for an animal to only react to salient cues (Zupanc, 2010). For many organisms, the detection of an approaching object, such as an oncoming conspecific or a predator, is particularly important. An approaching object with constant velocity is called looming, and has been widely studied for evoking avoidance behaviours in a number of animal species (Gibson, 1958). The migratory locust, Locusta migratoria, has been used extensively as a model system for visually guided behaviour, due to its robust collision-avoidance behaviours and its tractable nervous system (Schlotterer, 1977). The Lobula Giant Movement Detector (LGMD) and the Descending Contralateral Movement Detector (DCMD) constitute one pathway in the locust visual system that integrates the entire field of view that has been implicated in coordinating these types of behaviours (Santer et al., 2006). Previous studies have found that the LGMD/DCMD pathway responds to many visual stimuli, including complex scenes (Rind and Simmons, 1992), approaching paired objects (Guest and Gray, 2006), objects with compound shapes (Guest and Gray, 2006), and objects that follow compound trajectories (McMillan and Gray, 2012). These findings suggest that this pathway is capable of encoding complex motion such as exists in the locust’s natural environment. In my first objective (Chapter 2), I tested the response of the locust DCMD to increasingly complex motion. Using computer generated disks that followed compound trajectories with different velocities, I demonstrate that the DCMD is capable of encoding the location, trajectory, and velocity of an approaching object through aspects of the response profile over time. The motor systems of invertebrates are often controlled by ensembles of neurons working together (Dubuc et al., 2008; Hedrich et al., 2011; Gonzalez-Bellido et al., 2013). The locust visual system has at least five identified descending neurons, beyond the DCMD, that respond to visual motion (Rowell, 1971; Griss and Rowell, 1986; Gray et al., 2010). Due to the tractability of extracellular recordings of the DCMD, these neurons remain relatively little studied. Furthermore, their responses to stimuli have not been investigated concurrently. With recent advancements in multichannel recordings and spike sorting algorithms, it is now possible to explore the responses of multiple neurons in the locust system together. In my second objective (Chapter 3), I recorded from the connective of the locust using multichannel electrodes while challenging it with a wide array of visual stimuli. Preliminary results of these experiments identified as many as five neuronal units with distinctive firing patterns, some which appear to be novel. Together, these results illustrate that the locust visual system is more complex than previously thought, through both the abilities of a single neuron to encode many aspects of visual motion and the presence of multiple unique, visually-sensitive neurons.

A Hierarchical Hexagon Data Structure for Collision Detection

Kang, Ting-wei 28 July 2001 (has links)
In this paper, hexagonal grid is extended to hierarchical structure. This technique can be applied to collision detection. By using concept of node, we develop an effectually linear decode called ¡§HCD¡¨. To develop to three dimensions, the structure of octahedron is applied to develop hexagonal hierarchical structure in three dimensions. This is helpful to simulate objects and approximate objects. The object¡¦s data is commonly deposited in float. In this paper, Symmetrical Hexagonal Frame makes whole object to be deposited in integer. So the data of object can be compressed to smaller size. Otherwise, by concept of k-dops, we can close to object¡¦s real surfaces with hierarchical hexagonal structures at low level.

Development and Evaluation of a Virtual Haptic Environment

Lin, Chun-yu 13 July 2004 (has links)
As the progress of computer, virtual reality has become a more and more widespread technology and is applied extensively in entertainment, training, or medical science. To increase the interaction and reality of the virtual technology, the development of haptic feedback improves rapidly in recent years. This paper focuses on judgment existing collision detection algorithms, virtual wall models, and friction models from the view point of man-machine interface. A virtual environment interface with force feedback by using a joystick for computer game as a haptic device is established. A virtual environment is also built by employing the DirectX, a 3D computer graphic software developed by Microsoft Corp. Three virtual wall models are compared and four operational experiments are conducted to explore the influence of force feedback on operation task in virtual environment.

An evaluation of grid based broad phase collision detection for real time interactive environments

Liljeby, Jonas January 2011 (has links)
Detailed and exact collision detection for large amounts of objects has for a long time been a non real-time affair because of the immense amount of computations necessary. This was however not only because of the complexity of the algorithms but also because discussed of the computations would not have had to be done in the first place. This paper has through literature research and empirical testing examined two different broad phase approaches to object culling in a three dimensional environment. The aim of such a broad phase algorithm is to decrease the amount of computation heavy narrow phase collision detection checks and thus enhancing application performance. Potential weaknesses of these approaches were addressed and possible solutions discussed. Performance comparisons were made to give a better overview of what kind of performance enhancements can be expected and to give a theoretical base for further research.

Collision Detection for Moving Polyhedra

Canny, John 01 October 1984 (has links)
We consider the problem of moving a three dimensional solid object among polyhedral obstacles. The traditional formulation of configuration space for this problem uses three translational parameters and three angles (typically Euler angles), and the constraints between the object and obstacles involve transcendental functions. We show that a quaternion representation of rotation yields constraints which are purely algebraic in a higher-dimensional space. By simple manipulation, the constraints may be projected down into a six dimensional space with no increase in complexity. Using this formulation, we derive an efficient exact intersection test for an object which is translating and rotating among obstacles.

System for collision detection between deformable models built on axis aligned bounding boxes and GPU based culling /

Tuft, David O. January 2007 (has links) (PDF)
Thesis (M.S.)--Brigham Young University. Dept. of Computer Science, 2007. / Includes bibliographical references (p. 59-61).

Automatic Mesh Decomposition for Real-time Collision Detection

Bäcklund, Henrik, Neijman, Niklas January 2014 (has links)
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.

Swept areas and collision detection with application to autonomous vehicles

Sundberg, Sofia January 2005 (has links)
This thesis presents an algorithm for collision detection for an autonomous articulated vehicle following pregenerated paths in a mining environment. Two types of vehicles are studied. The tricycle vehicle and the articulated vehicle. The characteristics of the mine is presented. A way of using these characteristics is studied. An algorithm for collision detection using the swept area of the vehicle following a pregenerated path is given. As proof of concept a small implementation is also given along, with a few examples. / Validerat; 20101217 (root)

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