Rubén Jesús García

Post-processing NPR effects for video games

This paper describes different interactive, non photorealistic techniques which can be easily applied to video games. Based on a study of art and games, an emphasis is put on considering NPR tools as basic elements to provide different styles and moods, to convey different emotional and experiential representations of a game. We restrict ourselves to screen based effects, which permits any existing game to use our framework with practically no integration cost. This allows us not only to comply with user preferences in rendering style, but also the creation of multiple gaming experiences out of the same game. We show the resulting effects in an in-house videogame and in standard Unity demos, and show how the users can change the style of the videogame by means of a menu.

There is noisy lunch: A study of noise in evolutionary optimization problems

Noise or uncertainty appear in many optimization processes when there is not a single measure of optimality or fitness but a random variable representing it. These kind of problems have been known for a long time, but there has been no investigation of the statistical distribution those random variables follow, assuming in most cases that it is distributed normally and, thus, it can be modelled via an additive or multiplicative noise on top of a non-noisy fitness. In this paper we will look at several uncertain optimization problems that have been addressed by means of Evolutionary Algorithms and prove that there is no single statistical model the evaluations of the fitness functions follow, being different not only from one problem to the next, but in different phases of the optimization in a single problem.

Description and Solution of an Unreported Intrinsic Bias in Photon Mapping Density Estimation with Constant Kernel

This paper presents an analysis of the irradiance estimator often used in photon mapping algorithms and concludes that the classical approach with a constant kernel overestimates the correct value. We propose a new estimator that solves this problem and provide both theoretical and empirical studies to verify it.

Interactive global illumination for quasi-static scenes

This paper describes an approach to obtain interactive recalculation of global illumination for scenes with small moving objects (with respect to the complete geometry), on a standard PC, using density estimation techniques

An Importance Sampling Method for Arbitrary BRDFs

This paper introduces a new BRDF sampling method with reduced variance, which is based on a hierarchical adaptive PDF. This PDF also is based on rejection sampling with a bounded average number of trials, even in regions where the BRDF exhibits high variations. Our algorithm works in an appropiate way with both physical, analytical and measured reflectance models. Reflected directions are sampled by using importance sampling of the BRDF times the cosine term. This fact improves computation of reflected radiance when Monte-Carlo integration is used in Global Illumination.

The Uncertainty Quandary: A Study in the Context of the Evolutionary Optimization in Games and Other Uncertain Environments

In many optimization processes, the fitness or the considered measure of goodness for the candidate solutions presents uncertainty, that is, it yields different values when repeatedly measured, due to the nature of the evaluation process or the solution itself. This happens quite often in the context of computational intelligence in games, when either bots behave stochastically, or the target game possesses intrinsic random elements, but it shows up also in other problems as long as there is some random component. Thus, it is important to examine the statistical behavior of repeated measurements of performance and, more specifically, the statistical distribution that better fits them. This work analyzes four different problems related to computational intelligence in videogames, where Evolutionary Computation methods have been applied, and the evaluation of each individual is performed by playing the game, and compare them to other problem, neural network optimization, where performance is also a statistical variable. In order to find possible patterns in the statistical behavior of the variables, we track the main features of its distributions, skewness and kurtosis. Contrary to the usual assumption in this kind of problems, we prove that, in general, the values of two features imply that fitness values do not follow a normal distribution; they do present a certain common behavior that changes as evolution proceeds, getting in some cases closer to the standard distribution and in others drifting apart from it. A clear behavior in this case cannot be concluded, other than the fact that the statistical distribution that fitness variables follow is affected by selection in different directions, that parameters vary in a single generation across them, and that, in general, this kind of behavior will have to be taken into account to adequately address uncertainty in fitness in evolutionary algorithms.

Updated GameTools: Libraries for Easier Advanced Graphics in Serious Gaming

Advanced graphics effects can be difficult to create and implement by nonexperts. We present here multiplatform, multigame engine libraries, designed to simplify the use of efficient state-of-the-art computer graphics algorithms in the fields of geometry and illumination. A summary of our experiences updating and porting the libraries is included, with recommendations possibly useful to other programmers. The main features of the updated libraries are described. Two serious games which use the geometry libraries are presented here as use cases, both dealing with teaching history to middle school students. Finally, we show an implementation of a board game played in Europe since roman times (of interest to museums specialized in medieval or roman times) which uses the illumination libraries.

Test Installation of a Marker-Based Framework for Structural Health Monitoring of Bridges

Regular health monitoring of bridges is a vital process to prevent serious structural damage. Marker-based systems, which follow the trajectory of objects by placing a well-characterized pattern on their surface and identify them on photos or videos taken of these objects, have proven to be a cheap and flexible alternative for such tasks. In this work, we extend our previous laboratory implementation with a low-cost, fully automatic on-site installation at the bridge at Arosa Island, Galicia, Spain. Preliminary results presented in this paper show that our system is highly robust for the harsh climate of the installation site.

Marker-Based Framework for Structural Health Monitoring of Civil Infrastructure

As no civil infrastructure can escape aging and deterioration, health monitoring can prevent and report serious structural damage. With the rapid evolution of computer vision algorithms, optical-based systems become an increasingly feasible option for automatic monitoring. This paper proposes a cheap and flexible standalone system based on marker tracking to report deflection of structural elements of civil infrastructure. A single marker is placed on tracked objects, which allows unambiguous identification of objects and accurate movement tracking. Accuracy of the system is discussed by presenting a theoretical analysis of the translation error. Additionally, as a proof of concept we extend our work with a low-cost laboratory test implementation.

Un algoritmo de muestreo exacto para BRDFs arbitrarias

Resumen Este trabajo presenta un algoritmo para el muestreo eficiente y exacto de BRDF genericas, esto es, apto paracualquiera de los modelos de BRDFs analiticos o adquiridos de la literatura de informatica grafica. Nuestroobjetivo principal consiste en proporcionar una funcion de probabilidad utilizable en algoritmos de iluminacionglobal basados en metodos de Monte-Carlo, que permita un muestreo por importancias proporcional al productode la funcion BRDF y un termino coseno. Mediante la subdivision adaptativa de la BRDF en el disco unidad,obtenemos una estructura jerarquica o quadtree que nos permite aplicar un muestreo por rechazo optimizado enlos nodos. El numero medio de intentos en el muestreo esta acotado y es parametro de la estructura utilizada. Elmetodo se aplica al muestreo de cualquier modelo de BRDF sin necesidad de guia por parte del usuario. CategoriesandSubjectDescriptors (accordingtoACMCCS) : I.3.7[ComputerGraphics]:Three-DimensionalGrap-hics and Realism. Color, shading, shadowing, and texture