1,360 research outputs found
Measuring Visual Consistency in 3D Rendering Systems
One of the major challenges facing a present day game development company is the removal of bugs from such complex virtual environments. This work presents an approach for measuring the correctness of synthetic scenes generated by a rendering system of a 3D application, such as a computer game. Our approach builds a database of labelled point clouds representing the spatiotemporal colour distribution for the objects present in a sequence of bug-free frames. This is done by converting the position that the pixels take over time into the 3D equivalent points with associated colours. Once the space of labelled points is built, each new image produced from the same game by any rendering system can be analysed by measuring its visual inconsistency in terms of distance from the database. Objects within the scene can be relocated (manually or by the application engine); yet the algorithm is able to perform the image analysis in terms of the 3D structure and colour distribution of samples on the surface of the object. We applied our framework to the publicly available game RacingGame developed for Microsoft(R) Xna(R). Preliminary results show how this approach can be used to detect a variety of visual artifacts generated by the rendering system in a professional quality game engine
English Bankrupts 1732-1831: A Social Account
During the long eighteenth century in England many thousands of men and women became bankrupts, but little is known today about what they experienced as bankrupts. This study seeks to redress this imbalance by giving an account of the social experience of a wide and varied sample of English bankrupts from between the years 1732 and 1831. Through the employment of twenty-four case studies this study introduces the reader to some very different members of the English middling sort, all of whom, however, were engaged in a trade at which they failed. Some of these bankrupts were the predictable tropes of bankers and merchants who risked too much, but others were small provincial businessmen and shopkeepers. This study therefore challenges notions that bankruptcy was largely an event affecting only speculators and the extravagant. Each case study is supported by a variety of sources, for example, law court and bankruptcy commission records, personal correspondence, private journals, self-published exculpatory pamphlets and press reports. Together the sources reveal bankruptsâ personal experience, their beliefs, attitudes, anxieties, reflections and introspections. The social and cultural climate that surrounded bankrupts is represented by a range of polemical pamphlets and treatises, newspaper columns, advice literature, novels, verse and plays. Bankruptcy was not always the soft-option choice of the privileged. There was a larger overlap between the regimes of imprisonment for debt and bankruptcy in England in the long eighteenth century than is often supposed. This study will show that it was because all traders faced the real prospect of being summarily flung into debtorsâ gaol, that bankruptcies were triggered. The study explores bankruptsâ relationships with family and friends and finds how these connections continued to represent the most vital safety net against poverty, and how dire the consequences were when these affinities failed. Space and time were transformed for bankrupts as the law deprived them of freedom to move and trapped them in proceedings of indeterminate duration. Finally, the study assesses how bankrupts and their families experienced sudden financial and personal loss, and how they responded to, and came to terms with, downward social mobility. They lost property, public roles, status, often their health, and even their lives. However, as this study shows, not all bankrupts were equal in the degree to which their experience was unpleasant or tragic. Some sank, whilst others rose to the surface again to lead, often different, new lives
The Yamabe problem on Dirichlet spaces
We continue our previous work studying critical exponent semilinear elliptic
(and subelliptic) problems which generalize the classical Yamabe problem. In
[3] the focus was on metric-measure spaces with an `almost smooth' structure,
with stratified spaces furnishing the key examples. The criterion for
solvability there is phrased in terms of a strict inequality of the global
Yamabe invariant with a `local Yamabe invariant', which captures information
about the local singular structure. All of this is generalized here to the
setting of Dirichlet spaces which admit a Sobolev inequality and satisfy a few
other mild hypotheses. Applications include a new approach to the nonspherical
part of the CR Yamabe problem.Comment: 25 page
A toolbox for animal call recognition
Monitoring the natural environment is increasingly important as habit degradation and climate change reduce theworldâs biodiversity.We have developed software tools and applications to assist ecologists with the collection and analysis of acoustic data at large spatial and temporal scales.One of our key objectives is automated animal call recognition, and our approach has three novel attributes. First, we work with raw environmental audio, contaminated by noise and artefacts and containing calls that vary greatly in volume depending on the animalâs proximity to the microphone. Second, initial experimentation suggested that no single recognizer could dealwith the enormous variety of calls. Therefore, we developed a toolbox of generic recognizers to extract invariant features for each call type. Third, many species are cryptic and offer little data with which to train a recognizer. Many popular machine learning methods require large volumes of training and validation data and considerable time and expertise to prepare. Consequently we adopt bootstrap techniques that can be initiated with little data and refined subsequently. In this paper, we describe our recognition tools and present results for real ecological problems
Nominal Narrowing
Nominal unification is a generalisation of first-order unification
that takes alpha-equivalence into account. In this paper, we study
nominal unification in the context of equational theories. We
introduce nominal narrowing and design a general nominal E-unification
procedure, which is sound and complete for a wide class of equational
theories. We give examples of application
Convergence in Finite Cournot Oligopoly with Social and Individual Learning
Convergence to Nash equilibrium in Cournot oligopoly is a problem that recurrently arises as a subject of study in economics. The development of evolutionary game theory has provided an equilibrium concept more directly connected with adjustment dynamics and the evolutionary stability of the equilibria of the Cournot game has been studied by several articles. Several articles show that the Walrasian equilibrium is the stable evolutionary solution of the Cournot game. Vriend (2000) proposes to use genetic algorithm for studying learning dynamics in this game and obtains convergence to Cournot equilibrium with individual learning. We show in this article how social learning gives rise to Walras equilibrium and why, in a general setup, individual learning can effectively yield convergence to Cournot instead of Walras equilibrium. We illustrate these general results by computational experiments.Cournot oligopoly; Learning; Evolution; Selection; Evolutionary stability; Nash equilibrium; Genetic algorithms
Fixed-Point Constraints for Nominal Equational Unification
We propose a new axiomatisation of the alpha-equivalence relation for nominal terms, based on a primitive notion of fixed-point constraint. We show that the standard freshness relation between atoms and terms can be derived from the more primitive notion of permutation fixed-point, and use this result to prove the correctness of the new alpha-equivalence axiomatisation. This gives rise to a new notion of nominal unification, where solutions for unification problems are pairs of a fixed-point context and a substitution. Although it may seem less natural than the standard notion of nominal unifier based on freshness constraints, the notion of unifier based on fixed-point constraints behaves better when equational theories are considered: for example, nominal unification remains finitary in the presence of commutativity, whereas it becomes infinitary when unifiers are expressed using freshness contexts
Nominal C-Unification
Nominal unification is an extension of first-order unification that takes
into account the \alpha-equivalence relation generated by binding operators,
following the nominal approach. We propose a sound and complete procedure for
nominal unification with commutative operators, or nominal C-unification for
short, which has been formalised in Coq. The procedure transforms nominal
C-unification problems into simpler (finite families) of fixpoint problems,
whose solutions can be generated by algebraic techniques on combinatorics of
permutations.Comment: Pre-proceedings paper presented at the 27th International Symposium
on Logic-Based Program Synthesis and Transformation (LOPSTR 2017), Namur,
Belgium, 10-12 October 2017 (arXiv:1708.07854
A Primal-Dual Algorithm for Link Dependent Origin Destination Matrix Estimation
Origin-Destination Matrix (ODM) estimation is a classical problem in
transport engineering aiming to recover flows from every Origin to every
Destination from measured traffic counts and a priori model information. In
addition to traffic counts, the present contribution takes advantage of probe
trajectories, whose capture is made possible by new measurement technologies.
It extends the concept of ODM to that of Link dependent ODM (LODM), keeping the
information about the flow distribution on links and containing inherently the
ODM assignment. Further, an original formulation of LODM estimation, from
traffic counts and probe trajectories is presented as an optimisation problem,
where the functional to be minimized consists of five convex functions, each
modelling a constraint or property of the transport problem: consistency with
traffic counts, consistency with sampled probe trajectories, consistency with
traffic conservation (Kirchhoff's law), similarity of flows having close
origins and destinations, positivity of traffic flows. A primal-dual algorithm
is devised to minimize the designed functional, as the corresponding objective
functions are not necessarily differentiable. A case study, on a simulated
network and traffic, validates the feasibility of the procedure and details its
benefits for the estimation of an LODM matching real-network constraints and
observations
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