This work presents an approach to effectively integrate into one unified modular fire simulation framework the major processes related to fire, namely: a burning process, chemical combustion, heat distribution, decomposition and deformation of burning solids, and rigid body simulation of the residue. Simulators for every stage are described, and the modular structure enables switching to different simulators if more accuracy or more interactivity is desired. A "Stable Fluids" based three gas system is used to model the combustion process, and the heat generated during the combustion is used to drive the flow of the hot air. Objects, if exposed to enough heat, ignite and start burning. The decomposition of the burning object is modeled as a level set method, driven by the pyrolysis process, where the burning object releases combustible gases. Secondary deformation effects, such as bending burning matches and crumpling burning paper, are modeled as a proxy based deformation. Physically based simulation, done at interactive rates, enables the user to ef- ficiently test different setups, as well as interact and change the conditions during the simulation. The graphics card is used to generate additional frames for real-time visualization. This work further proposes a method for controlling and directing high resolution simulations. An interactive coarse resolution simulation is provided to the user as a "preview" to control and achieve the desired simulation behavior. A higher resolution "final" simulation that creates all the fine scale behavior is matched to the preview simulation such that the preview and final simulations behave in a similar manner. In this dissertation, we highlighted a gap within the CG community for the simulation of fire. There has not previously been a physically based yet interactive simulation for fire. This dissertation describes a unified simulation framework for physically based simulation of fire and burning. Our results show that our implementation can model fire, objects catching fire, burning objects, decomposition of burning objects, and additional secondary deformations. The results are plausible even at interactive frame rates, and controllable.

Computers are being employed in a variety of ways by a variety of individuals to create imagery. Much work has been done to accurately model natural phenomena in the context of computer graphics as well as model specific artists' tools and techniques. Focusing on the dynamics of water flow across surfaces, it is the goal of this work to develop a physically inspired texturing tool that allows artists to create interesting staining and wearing effects on surfaces. Weathering or the wearing down of materials by natural forces can create complex and beautiful patterns on a variety of surfaces. In this process lies the very essence of the creative act. To distill the essence of the elements of the water staining process, we employ a computer generated particle system in a phenomenological model. The motion of these particles is controlled by physically based constraints, such as wind, gravity, mass, etc. The way in which each particle interacts with or modifies the look of the surface is further controlled by parameters such as surface roughness, surface color and surface hardness. Each particle can remove or deposit material as it flows across the surface, creating complex patterns.

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Background The increase in screen resolution has increased from HD to Ultra-HDduring the last decade. A modern game today with Ultra-HD resolution has overeight million pixels that need to be shaded, combined with the expensive shadingmethod Physically Based Rendering the equations needed to calculate each pixel arenumerous. Objectives This the study aims to remove complexity from the Physically BasedRendering shading method in the form of roughness in low-lit areas. The low-lit areaswill instead be rendered without the roughness attribute. By removing roughnessless calculations will be performed. Methods To remove roughness from low-lit areas the light had to be approximatedusing a diffuse model. The pixel was later converted via Hue Saturation PerceivedBrightness to calculate the brightness. If the pixel was under the given threshold,the pixel was shaded using a low-complexity Physically Based Rendering implemen-tation without roughness. A user study was conducted using Unity game enginewith eight participants being asked to compare different stimuli all rendered withdifferent thresholds for darkness with a reference picture. The aim of the study wasto ascertain if the stimuli without roughness had any perceivable difference from thereference. Results The results of the study show the majority of the participants noticinga difference when comparing the stimuli with the reference. The areas affected wasnot only the low-lit areas but the whole scene. The energy conversion without theroughness value made the whole scene appear darker. Conclusions The roughness value is an integral part of energy conversion andwithout it, the scene will appear much darker. While the majority of participantsnoticed a difference, the lowest threshold resembled the original the most

Background. In the pursuit of realism in rendering, a feature that may get overlooked is the sky and atmosphere—especially the consumer who might suspect that something is off without identifying it. A critical aspect of sky rendering is the color that should be dynamic with the time of day to be realistic. With multiple ways of rendering a sky and atmosphere, it is unclear which method best suits the circumstance. Objectives. The objective of this study was to make that decision clearer with both the visual aspect and the realism. It was also crucial that performance was not affected too heavily by the techniques. Methods. As the first objective can be subjective, we decided to ask several people through a survey to get a more objective answer. In the survey, we presented the participants with two images of identical scenes where the only difference between them was the method of rendering the sky. We then asked them which picture they thought was the most aesthetically pleasing and which they thought was the most realistic. The second part of the study was to test the performance of the techniques. We recorded the average frame time through a C\# script over all of the scenes. Results. When using the settings we established, the Physically-based atmosphere scored lower in both realism and aesthetics in the first visual test but scored higher in realism in all of the scenarios for the second visual test. Both the average frame rate and frame time did end up in favor of the Physically based atmosphere. Conclusions. The outcome of this study was surprising, we had thought that the Physically-based atmosphere would score higher in both realism and aesthetics. The performance of the Physically based atmosphere method proved to be much more optimized than the Unity procedural skybox than we would have thought.

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<p>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.</p><p>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.</p><p>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.</p><p>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.</p><p>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.</p><p>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 actors<i>i.e.</i>groups that have similar views with regard to theroad alternatives.</p><p><b>Keywords:</b>Physically-based groundwater modelling,contamination, flow and solute transport, glaciofluvialdeposits, Nybroåsen, Sweden, and multi-criteriadecision-aid.</p>

La compréhension et la mémorisation de données visuelles sont une part importante de l'apprentissage des étudiants en médecine. Cependant, la nature tridimensionnelle et dynamique du corps humain pose de nombreux problèmes. Leur solution nécessite de véritables outils informatiques interactifs pour permettre aux étudiants de créer et de manipuler des données complexes. Nous proposons dans ce but plusieurs approches. Tout d'abord, nous nous sommes intéressés à l'animation par modèles physiques de matériaux élastiques anisotropes. Son utilisation pendant un cours d'anatomie physiologique du myocarde offre la possibilité aux étudiants de construire des échantillons de tissu musculaire cardiaque. Pour atteindre cet objectif, notre modèle présente deux caractéristiques importantes : la première est un faible coût en temps de calcul afin atteindre un affichage interactif ; la seconde est une apparence intuitive qui facilite son contrôle par l'utilisateur. Ensuite, nous nous sommes intéressés à l'interaction en trois dimensions à l'aide d'interfaces bidimensionnelles, en vue de l'annotation de modèles existants, ou de la création de nouveaux modèles. Cette approche tire parti du fait que le dessin est encore considéré comme une importante méthode d'apprentissage par certains professeurs français d'anatomie. Notre système de dessin 3D possède une représentation des traits de l'utilisateur qui permet l'affichage d'un même dessin sous plusieurs points de vue. Cette représentation est d'ailleurs compatible avec celle de surfaces polygonales existantes, qui peuvent ainsi être annotées. De manière complètement différente, notre outil de modélisation par le dessin utilise conjointement les informations provenant de la géométrie des traits et de l'analyse de l'image produite, afin de créer des modèles en trois dimensions sans passer par une spécification explicite de la profondeur.

We present methods for incorporating bubbles into a photorealistc fluid simulation. Previous methods of fluid simulation in computer graphics do not include bubbles. Our system automatically creates bubbles, which are simulated on top of the fluid simulation. These bubbles are approximated by spheres and are rendered with the fluid to appear as one continuous surface. This enhances the overall realism of the appearance of a splashing fluid for computer graphics. Our methods leverage the particle level set representation of the fluid surface. We create bubbles from escaped marker particles from the outside to the inside. These marker particles might represent air that has been trapped within the fluid surface. Further, we detect when air is trapped in the fluid and create bubbles within this space. This gives the impression that the air pocket has become bubbles and is an inexpensive way to simulate the air trapped in air pockets. The results of the simulation are rendered with a raytracer that includes caustics. This allows the creation of photorealistic images. These images support our position that the simple addition of bubbles included in a fluid simulation creates results that are much more true to life.

This thesis describes a method for using physically based techniques to model an explosion and the resulting side effects. Explosions are some of the most visually exciting phenomena known to humankind and have become nearly ubiquitous in action films. A realistic computer simulation of this powerful event would be cheaper, quicker, and much less complicated than safely creating the real thing. The immense energy released by a detonation creates a discontinuous localized increase in pressure and temperature. Physicists and engineers have shown that the dissipation of this concentration of energy, which creates all the visible effects, adheres closely to the compressible Navier-Stokes equation. This program models the most noticeable of these results. In order to simulate the pressure and temperature changes in the environment, a three dimensional grid is placed throughout the area around the detonation and a discretized version of the Navier-Stokes equation is applied to the resulting voxels. Objects in the scene are represented as rigid bodies that are animated by the forces created by varying pressure on their hulls. Fireballs, perhaps the most awe-inspiring side effects of an explosion, are simulated using massless particles that flow out from the center of the blast and follow the currents created by the dissipating pressure. The results can then be brought into Maya for evaluation and tweaking.