O crescente número de sistemas de animação que utilizam a cinemática para gerar movimento de objetos vem levando os pesquisadores a buscar outras alternativas para produzir resultados mais realistas. Com base nesta premissa, vários autores começaram a estudar a geração de movimento de objetos sintéticos através da aplicação da dinâmica. Assim surgiram os modelos baseados em leis físicas. Num primeiro momento foram abordados apenas objetos rígidos, passando-se mais tarde a considerar objetos articulados e, por fim, aqueles com características elásticas, também denominados de objetos flexíveis ou deformáveis. O objetivo principal do trabalho é a definição de um modelo para simulação de objetos deformáveis no espaço euclidiano. São abordados tanto o modelo geométrico utilizado como o modelo físico, sendo ressaltadas as forças aplicadas sobre o objeto e as restrições que podem ser impostas pelo mundo virtual no qual o mesmo está inserido. Dentre as forças descritas, pode-se destacar: força gravitacional, elasticidade, força de curvatura e torção, colisão e atrito. A fundamentação do trabalho desenvolvido é apresentada na forma de uma introdução aos sistemas de animação, enfatizando os sistemas baseados em leis físicas e de uma revisão bibliográfica dos métodos de deformação existentes. No que diz respeito à colisão de objetos elásticos, são descritos tanto os métodos estudados para a solução das mesmas, como as técnicas para detecção do choque. A simulação do movimento é descrita sob dois aspectos: o algoritmo utilizado para a geração do movimento e a integração numérica das equações diferenciais no tempo. É abordado ainda, em detalhe, o protótipo desenvolvido com o propósito de validar o modelo proposto, sendo descrita a linguagem criada a fim de permitir a especificação da animação e parâmetros diversos do modelo. Por fim, são apresentados e avaliados os resultados obtidos através do desenvolvimento do modelo proposto por intermédio do protótipo FLEX3D. É dedicada ainda especial atenção às perspectivas futuras deste trabalho. / The growing number of animation systems that use kinematics to generate the motion of objects have led to other alternatives to produce more realistic results. Some authors began to study the animation of synthetic objects through the application of the dynamic concepts, creating the modern physically based models. At first, only rigid objects were treated; later on articulated objects were considered. At last, those with elastic characteristics (called flexible or deformable objects) were taken into consideration. The main goal of this work is to define a simulation model for deformable objects in the euclidean space. Both the geometric and the physical models are presented, considering the forces applied to the object and the constraints defined by the virtual world. Described forces include gravity, elasticity, dumping force, collision and attrition. This work presents an introduction to animation systems focusing the physically based systems. After this, a bibliographic review of the existent deformation methods is made. Methods for detecting and solving the collision between two elastic objects are described. Two aspects of the motion simulation are described: the algorithm used to generate the motion and the numeric integration of the differential equations in time. A prototype named FLEX3D is presented to validate the proposed model. The language used for specifying the animation is described and results obtained through the use of FLEX3D are also presented. Special attention is given to the possible future works.

Placé à la frontière entre l'informatique graphique et la physique, le rendu d'image physiquement réaliste est un domaine qui tente de créer des images en simulant le comportement optique des matériaux. Les applications sont multiples : restauration virtuelle d'oeuvre du patrimoine, simulation d'effets optiques, rendu industriel pour la conception, voire même, conception assistée par ordinateur de la couleur. Cette thèse présente les travaux réalisés au cours du projet Virtuelium, un logiciel de rendu d'image physiquement réaliste dont la quatrième version a été développée dans le cadre de cette thèse. Elle en présente les principes et méthodologies utilisés pour les mesures et la validation des résultats. Nous présentons aussi plusieurs travaux réalisés durant cette thèse avec cet outil : de la restauration virtuelle à la bio-photonique sans oublier un aperçu de rendu de "matériaux à effet", pour des applications industrielles (peintures, encres, cosmétiques, etc.). / Laying between computer graphics and physics, the rendering of physically based images is a domain that attempt to create images by simulating the optical behaviour of materials interacting with light (either natural or not). There are several applications : virtual restoration of cultural heritage artefacts, simulation of optical effects, industrial rendering for design and even computer-aided design of colour. This thesis presents the works realised within Virtuelium project framework, a physically based rendering software. The fourth version was developed during this thesis. Here will be presented the principles and methodologies involved for the measurements and the validation of the obtained results. We present also several works that have been done during that thesis using Virtuelium: from virtual restoration to bio-photonics, including an overview of iridescent pigments rendered for an industrial purpose.

O crescente número de sistemas de animação que utilizam a cinemática para gerar movimento de objetos vem levando os pesquisadores a buscar outras alternativas para produzir resultados mais realistas. Com base nesta premissa, vários autores começaram a estudar a geração de movimento de objetos sintéticos através da aplicação da dinâmica. Assim surgiram os modelos baseados em leis físicas. Num primeiro momento foram abordados apenas objetos rígidos, passando-se mais tarde a considerar objetos articulados e, por fim, aqueles com características elásticas, também denominados de objetos flexíveis ou deformáveis. O objetivo principal do trabalho é a definição de um modelo para simulação de objetos deformáveis no espaço euclidiano. São abordados tanto o modelo geométrico utilizado como o modelo físico, sendo ressaltadas as forças aplicadas sobre o objeto e as restrições que podem ser impostas pelo mundo virtual no qual o mesmo está inserido. Dentre as forças descritas, pode-se destacar: força gravitacional, elasticidade, força de curvatura e torção, colisão e atrito. A fundamentação do trabalho desenvolvido é apresentada na forma de uma introdução aos sistemas de animação, enfatizando os sistemas baseados em leis físicas e de uma revisão bibliográfica dos métodos de deformação existentes. No que diz respeito à colisão de objetos elásticos, são descritos tanto os métodos estudados para a solução das mesmas, como as técnicas para detecção do choque. A simulação do movimento é descrita sob dois aspectos: o algoritmo utilizado para a geração do movimento e a integração numérica das equações diferenciais no tempo. É abordado ainda, em detalhe, o protótipo desenvolvido com o propósito de validar o modelo proposto, sendo descrita a linguagem criada a fim de permitir a especificação da animação e parâmetros diversos do modelo. Por fim, são apresentados e avaliados os resultados obtidos através do desenvolvimento do modelo proposto por intermédio do protótipo FLEX3D. É dedicada ainda especial atenção às perspectivas futuras deste trabalho. / The growing number of animation systems that use kinematics to generate the motion of objects have led to other alternatives to produce more realistic results. Some authors began to study the animation of synthetic objects through the application of the dynamic concepts, creating the modern physically based models. At first, only rigid objects were treated; later on articulated objects were considered. At last, those with elastic characteristics (called flexible or deformable objects) were taken into consideration. The main goal of this work is to define a simulation model for deformable objects in the euclidean space. Both the geometric and the physical models are presented, considering the forces applied to the object and the constraints defined by the virtual world. Described forces include gravity, elasticity, dumping force, collision and attrition. This work presents an introduction to animation systems focusing the physically based systems. After this, a bibliographic review of the existent deformation methods is made. Methods for detecting and solving the collision between two elastic objects are described. Two aspects of the motion simulation are described: the algorithm used to generate the motion and the numeric integration of the differential equations in time. A prototype named FLEX3D is presented to validate the proposed model. The language used for specifying the animation is described and results obtained through the use of FLEX3D are also presented. Special attention is given to the possible future works.

O crescente número de sistemas de animação que utilizam a cinemática para gerar movimento de objetos vem levando os pesquisadores a buscar outras alternativas para produzir resultados mais realistas. Com base nesta premissa, vários autores começaram a estudar a geração de movimento de objetos sintéticos através da aplicação da dinâmica. Assim surgiram os modelos baseados em leis físicas. Num primeiro momento foram abordados apenas objetos rígidos, passando-se mais tarde a considerar objetos articulados e, por fim, aqueles com características elásticas, também denominados de objetos flexíveis ou deformáveis. O objetivo principal do trabalho é a definição de um modelo para simulação de objetos deformáveis no espaço euclidiano. São abordados tanto o modelo geométrico utilizado como o modelo físico, sendo ressaltadas as forças aplicadas sobre o objeto e as restrições que podem ser impostas pelo mundo virtual no qual o mesmo está inserido. Dentre as forças descritas, pode-se destacar: força gravitacional, elasticidade, força de curvatura e torção, colisão e atrito. A fundamentação do trabalho desenvolvido é apresentada na forma de uma introdução aos sistemas de animação, enfatizando os sistemas baseados em leis físicas e de uma revisão bibliográfica dos métodos de deformação existentes. No que diz respeito à colisão de objetos elásticos, são descritos tanto os métodos estudados para a solução das mesmas, como as técnicas para detecção do choque. A simulação do movimento é descrita sob dois aspectos: o algoritmo utilizado para a geração do movimento e a integração numérica das equações diferenciais no tempo. É abordado ainda, em detalhe, o protótipo desenvolvido com o propósito de validar o modelo proposto, sendo descrita a linguagem criada a fim de permitir a especificação da animação e parâmetros diversos do modelo. Por fim, são apresentados e avaliados os resultados obtidos através do desenvolvimento do modelo proposto por intermédio do protótipo FLEX3D. É dedicada ainda especial atenção às perspectivas futuras deste trabalho. / The growing number of animation systems that use kinematics to generate the motion of objects have led to other alternatives to produce more realistic results. Some authors began to study the animation of synthetic objects through the application of the dynamic concepts, creating the modern physically based models. At first, only rigid objects were treated; later on articulated objects were considered. At last, those with elastic characteristics (called flexible or deformable objects) were taken into consideration. The main goal of this work is to define a simulation model for deformable objects in the euclidean space. Both the geometric and the physical models are presented, considering the forces applied to the object and the constraints defined by the virtual world. Described forces include gravity, elasticity, dumping force, collision and attrition. This work presents an introduction to animation systems focusing the physically based systems. After this, a bibliographic review of the existent deformation methods is made. Methods for detecting and solving the collision between two elastic objects are described. Two aspects of the motion simulation are described: the algorithm used to generate the motion and the numeric integration of the differential equations in time. A prototype named FLEX3D is presented to validate the proposed model. The language used for specifying the animation is described and results obtained through the use of FLEX3D are also presented. Special attention is given to the possible future works.

This thesis describes methods for collision detection and collision response, implemented in a complete collision framework for both rigid and deformable bodies. The framework is intended to act as a base for new technologies regarding muscle and facial simulation for feature film production, at the visual effects studio MPC. Specifically, we implement sweep and prune as a first step in our collision detection for fast pruning of pairs, followed by optimized spatial hashing to decrease the amount of triangle intersection tests. Further, we use a constraint-based method for collision response based on iterative constraint anticipation, which provides several advantages in terms of accuracy compared to penalty- or impulse-based methods.

When creating materials in computer graphics, the most common method is to estimate the properties based on intuition. This seems like a flawed approach, seeing as a big part of the industry has already moved to a physically based workflow. A better method would be to observe real material properties, and use that data in the application. This research delves into the art of material creation by first explaining the theory behind the properties of materials through a literature review. The review also reveals techniques that separate and visually presents these properties to artists, giving them a better understanding of how a material behaves. Through action research, an empirical study then presents a workflow for creating photorealistic renders using data collected with these techniques. While the techniques still require subjective decisions when recreating the materials, they do help artists create more accurate renderings with less guesswork.

Title: Colour reproduction accuracy of stochastic spectral sampling: an experi- mental evaluation Author: Bc. Attila Hencz �attila.hencz@matfyz.cz� Department: Department of Software and Computer Science Education Supervisor: doc. Alexander Wilkie, Dr. �wilkie@cgg.mff.cuni.cz�, Department of Software and Computer Science Education Abstract: We investigate the colorimetric accuracy of stochastic sampling in the wavelength domain for realistic rendering purposes. In particular, we consider the impact of three specific design choices in a rendering system on the accuracy of the overall result: how exactly spectral samples are splatted into the final result spectrum, how many spectral channels one uses in the result images, and the impact of Hero Wavelength Spectral Sampling (HWSS) compared to the stand- ard monochrome technique. We provide experimental results, comparisons and evaluation of sampling high-resolution spectra that originate from measurements of real paint samples found in colour atlases, and normed light sources defined by the CIE. The latter include both smooth and spiky spectra, so the used com- bination of reflectances and light spectra provides a representative body of input values that allows to draw conclusions that are relevant for practical rendering work. Keywords: physically based image...

Tensors are of great interest to many applications in engineering and in medical imaging, but a proper analysis and visualization remains challenging. Physics-based visualization of tensor fields has proven to show the main features of symmetric second-order tensor fields, while still displaying the most important information of the data, namely the main directions in medical diffusion tensor data using texture and additional attributes using color-coding, in a continuous representation. Nevertheless, its application and usability remains limited due to its computational expensive and sensitive nature. We introduce a novel approach to compute a fabric-like texture pattern from tensor fields on arbitrary non-selfintersecting surfaces that is motivated by image space line integral convolution (LIC). Our main focus lies on regaining three-dimensionality of the data under user interaction, such as rotation and scaling. We employ a multi-pass rendering approach to estimate proper modification of the LIC noise input texture to support the three-dimensional perception during user interactions.

In the recent decades, therehave been frequent conflicts between groundwater waterresources and environmentally hazardous activities. Newmethodologies for aiding decision-making in groundwater impactassessment and protection areneeded and in which issues ofincreased awareness, better understanding of the groundwaterresources processes, and validation of predictive mathematicalmodels are addressed. A framework fordecision–aid, based on predictive simulations that a)predicts the environmental impacts b) provides the totaleconomical value c) visualises the impacts and the groundwaterproperties and d) describes the uncertainties in the results isproposed herein. The framework can be applied in environmentalimpact assessments, strategic environmental assessments andprotection and management of water resources. The results ofthe model are used as feedback for determining new scenarios,depending on the required uncertainties, and if the plannedactivity is sustainable, and/or fulfils the legislative andpolicy measures. This framework is applied to a particular casestudy, Nybroåsen, in the south-eastern part of Sweden,where the highway E22 is constructed through the importantglaciofluvial esker aquifer, passing the protection zone of thewater supply for the Kalmar municipality. The impacts from the new highwayand the existing road have been predicted by two-dimensionalphysically based time-variant flow and solute groundwatermodelling. The results, breakthrough curves of contaminantconcentration in wells and maps of concentration distributions,as well as travel times, flow paths, and capture zones forwells determined by particle tracking have been presented. The constructed model of theNybroåsen study area was calibrated by comparing observedand simulated groundwater levels for 15 observation wells forten years of measurements. The model has been evaluated bothgraphically and numerically and the calibration target wasfulfilled for 13 of the 15 observation wells. The model workincludes investigations of the catchment information, a waterbalance study, simulation of the groundwater recharge,consideration of the unsaturated zone by a numerical columnsimulation, and sensitivity analysis. From the sensitivity analysis ofthe flow and transport parameters, it has been shown that theuncertainties are mainly due to the hydraulic conductivity.Comparison of the derived conductivity from the steady-stateautomatic calibration and the time-variant calibration showedthat there are major differences in the derived parameters,which illustrates the importance of a time dependentcalibration over both wet and dry periods and in more than onepoint in the area of interest of the model predictions. In addition, a multi-criteriadecision analysis has been carried out for four roadalternatives (including the new highway E22) and the existingroad in the case study concerned. The multi-criteria decisionaid is applied as an illustration of how it can be used in thestudy area to identify a) interest groups of actors and theirconcerns b) ranking of alternative road scenarios according toactors’preferences and c) coalition groups of actorsi.e.groups that have similar views with regard to theroad alternatives. <b>Keywords:</b>Physically-based groundwater modelling,contamination, flow and solute transport, glaciofluvialdeposits, Nybroåsen, Sweden, and multi-criteriadecision-aid. / NR 20140805

Groundwater is a sensitive component affected by climate change. Modelling the dynamics of groundwater levels is inherently difficult particularly as the response to climate change. Given this complexity, most of the current studies using long term groundwater time series were conducted by statistical analysis or using over simplified assumptions to represent the physical processes in hydrological system. With the objective of providing an improved physically based groundwater modelling approach to support climate change impact assessment, a dataset of long term time series of groundwater levels from two different soil types (sand and till) were selected from the Tärnsjö area located in southeast of Sweden. The CoupModel was chosen to perform the simulation since it offers a physically based representation on groundwater recharge processes. A two-step strategy for calibration with first short-term calibration followed by long-term testing was adopted. Simulated groundwater levels followed the general patterns of measured groundwater level dynamics; however, auto-correlations and periodicities were observed in residuals for all sites of which two sandy soil sites with deeper groundwater tables maintained strong auto-correlations in long time lags and an extra 15.4-year periodicity. The long memory of the system rendered it more susceptible to climate change. Uncertainty arises if different initial condition had been applied in short term period calibration.