Hierarchical path-finding for Navigation Meshes (HNA*)

Path-finding can become an important bottleneck as both the size of the virtual environments and the number of agents navigating them increase. It is important to develop techniques that can be efficiently applied to any environment independently of its abstract representation. In this paper we present a hierarchical NavMesh representation to speed up path-finding. Hierarchical path-finding (HPA*) has been successfully applied to regular grids, but there is a need to extend the benefits of this method to polygonal navigation meshes. As opposed to regular grids, navigation meshes offer representations with higher accuracy regarding the underlying geometry, while containing a smaller number of cells. Therefore, we present a bottom-up method to create a hierarchical representation based on a multilevel k-way partitioning algorithm (MLkP), annotated with sub-paths that can be accessed online by our Hierarchical NavMesh Path-finding algorithm (HNA*). The algorithm benefits from searching in graphs with a much smaller number of cells, thus performing up to 7.7 times faster than traditional A¿ over the initial NavMesh. We present results of HNA* over a variety of scenarios and discuss the benefits of the algorithm together with areas for improvement.Peer ReviewedPostprint (author's final draft

The minimum energy expenditure shortest path method

This article discusses the addition of an energy parameter to the shortest path execution process; namely, the energy expenditure by a character during execution of the path. Given a simple environment in which a character has the ability to perform actions related to locomotion, such as walking and stair stepping, current techniques execute the shortest path based on the length of the extracted root trajectory. However, actual humans acting in constrained environments do not plan only according to shortest path criterion, they conceptually measure the path that minimizes the amount of energy expenditure. On this basis, it seems that virtual characters should also execute their paths according to the minimization of actual energy expenditure as well. In this article, a simple method that uses a formula for computing vanadium dioxide ($VO_2$) levels, which is a proxy for the energy expenditure by humans during various activities, is presented. The presented solution could be beneficial in any situation requiring a sophisticated perspective of the path-execution process. Moreover, it can be implemented in almost every path-planning method that has the ability to measure stepping actions or other actions of a virtual character

The Face of Urban Poverty Explaining the Prevalence of Slums in Developing Countries

One of the most visible and enduring manifestations of urban poverty in developing countries is the formation and proliferation of slums. While attention has focused on the rapid pace of urbanization as the sole or major factor explaining the proliferation of slums and squatter settlements in developing countries, there are other factors whose impacts are not known with much degree of certainty. It is also not clear how the effects of these factors vary across regions of the developing world. This paper accounts for differences in the prevalence of slums among developing countries using data drawn from the recent global assessment of slums undertaken by the United Nations Human Settlements Programme. The empirical analysis identifies substantial inter-country variations in the incidence of slums both within and across the regions of Africa, Asia as well as, Latin America and the Caribbean. Further analysis indicates that higher GDPurban poverty, slums, developing countries, inter-country differences

Non-invasive airway health assessment: Synchrotron imaging reveals effects of rehydrating treatments on mucociliary transit in-vivo

To determine the efficacy of potential cystic fibrosis (CF) therapies we have developed a novel mucociliary transit (MCT) measurement that uses synchrotron phase contrast X-ray imaging (PCXI) to non-invasively measure the transit rate of individual micron-sized particles deposited into the airways of live mice. The aim of this study was to image changes in MCT produced by a rehydrating treatment based on hypertonic saline (HS), a current CF clinical treatment. Live mice received HS containing a long acting epithelial sodium channel blocker (P308); isotonic saline; or no treatment, using a nebuliser integrated within a small-animal ventilator circuit. Marker particle motion was tracked for 20 minutes using PCXI. There were statistically significant increases in MCT in the isotonic and HS-P308 groups. The ability to quantify in vivo changes in MCT may have utility in pre-clinical research studies designed to bring new genetic and pharmaceutical treatments for respiratory diseases into clinical trials.Martin Donnelley, Kaye S. Morgan, Karen K. W. Siu, Nigel R. Farrow, Charlene S. Stahr, Richard C. Boucher, Andreas Fouras & David W. Parson

CREATe 2012-2016: Impact on society, industry and policy through research excellence and knowledge exchange

On the eve of the CREATe Festival May 2016, the Centre published this legacy report (edited by Kerry Patterson & Sukhpreet Singh with contributions from consortium researchers)

Low-Stress Bicycling and Network Connectivity

For a bicycling network to attract the widest possible segment of the population, its most fundamental attribute should be low-stress connectivity, that is, providing routes between people’s origins and destinations that do not require cyclists to use links that exceed their tolerance for traffic stress, and that do not involve an undue level of detour. The objective of this study is to develop measures of low-stress connectivity that can be used to evaluate and guide bicycle network planning. We propose a set of criteria by which road segments can be classified into four levels of traffic stress (LTS). LTS 1 is suitable for children; LTS 2, based on Dutch bikeway design criteria, represents the traffic stress that most adults will tolerate; LTS 3 and 4 represent greater levels of stress. As a case study, every street in San Jose, California, was classified by LTS. Maps in which only bicycle-friendly links are displayed reveal a city divided into islands within which low-stress bicycling is possible, but separated from one another by barriers that can be crossed only by using high-stress links. Two points in the network are said to be connected at a given level of traffic stress if the subnetwork of links that do not exceed the specified level of stress connects them with a path whose length does not exceed a detour criterion (25% longer than the most direct path). For the network as a whole, we demonstrate two measures of connectivity that can be applied for a given level of traffic stress. One is “percent trips connected,” defined as the fraction of trips in the regional trip table that can be made without exceeding a specified level of stress and without excessive detour. This study used the home-to-work trip table, though in principle any trip table, including all trips, could be used. The second is “percent nodes connected,” a cruder measure that does not require a regional trip table, but measures the fraction of nodes in the street network (mostly street intersections) that are connected to each other. Because traffic analysis zones (TAZs) are too coarse a geographic unit for evaluating connectivity by bicycle, we also demonstrate a method of disaggregating the trip table from the TAZ level to census blocks. For any given TAZ, origins in the home-to-work trip table are allocated in proportion to population, while destinations are allocated based on land-use data. In the base case, the fraction of work trips up to six miles long that are connected at LTS 2 is 4.7%, providing a plausible explanation for the city’s low bicycling share. We show that this figure would almost triple if a proposed slate of improvements, totaling 32 miles in length but with strategically placed segments that provide low-stress connectivity across barriers, were implemented

Livelihoods analysis of landmine affected communities in Yemen (Volume I: main report)

The government of Yemen is committed to the complete elimination of landmines and explosive remnants of war. The National Mine Action Committee (NMAC) was established in June 1998 to formulate policy, allocate resources, and develop a national mine-action strategy. Furthermore, the Yemen Executive Mine Action Centre (YEMAC) was established in January 1999 as the implementing body of the NMAC with the primary responsibility of coordinating all mine-action activities in the country. The aim of the current Strategic Mine Action Plan is to put an end to the suffering and casualties caused by anti-personnel landmines, by the end of March 2009. As of September 2005, over 240 million square meters of affected land have been surveyed, cleared and returned to the local users. In 2005, the Mid-term Evaluation for strengthening national capacity for mine action in Yemen praised the achievements of YEMAC and NMAC to date, and also recommended that Community Rehabilitation become an integral part of mine action in Yemen in the future. This study was commissioned by YEMAC and the Geneva International Centre for Humanitarian Demining (GICHD), with the following objectives: 1. To assess the overall socio-economic returns from mine clearance investments; 2. to make a preliminary assessment of complementary development initiatives for mine-affected communities: and 3. to enhance the capacity of YEMAC to conduct future assessments of socio-economic benefits from mine action; assess the community Landmine Impact Scores as a tool for identifying impact and determining priorities for action; advise on how to design and conduct on-going socio-economic surveys relating to ERW; advise on integrating social differentiation within LIS survey protocols, and advise on enhancements to YEMAC’s monitoring and evaluation system

A Grid-Based Motion Planning Approach for Coherent Groups

This paper presents a novel motion planning approach for coherent groups with constant area, and it integrates C-L method into the probabilistic roadmap algorithm with sampling on the medial axis (MAPRM). In the preprocessing phase, the group is discretized into a grid-set which represents the configuration of the group. Then, a number of samples are generated on workspace by medial axis technique. These samples are extended into group’s configuration nodes of the roadmap using an extending strategy. Also, the group's deformation degree relative to the desired shape is introduced to improve the evaluation function. It gives users more flexibility to determine the respective weights of the group’s deformation degree and its distance to the goal in the query phase. After that, a novel local planner is constructed to connect any two neighbor configurations by using C-L method and the improved evaluation function. Experiments show that our approach is able to find paths for the coherent group efficiently and keep its area invariant when moving toward the goal