Desertscape Simulation

International audienceWe present an interactive aeolian simulation to author hot desert scenery. Wind is an important erosion agent in deserts which, despite its importance, has been neglected in computer graphics. Our framework overcomes this and allows generating a variety of sand dunes, including barchans, longitudinal and anchored dunes, and simulates abrasion which erodes bedrock and sculpts complex landforms. Given an input time varying high altitude wind field, we compute the wind field at the surface of the terrain according to the relief, and simulate the transport of sand blown by the wind. The user can interactively model complex desert landscapes, and control their evolution throughout time either by using a varietyof interactive brushes or by prescribing events along a user-defined time-line

Modeling of erosion impact on geometric objects

Simulace eroze je důležitým problémem v oblasti počítačové grafiky. Nejvýznamnějšími erozními procesy v přírodě jsou zvětrávání a hydraulická eroze. Mnoho metod se těmito problémy zabývá, ale většinou jsou tyto metody založeny na výškových mapách nebo volumetrických datech. Výškové mapy neumožňují simulaci složitých plně trojrozměrných scén, zatímco volumetrická data mají vysoké paměťové nároky. Tato disertační práce zkoumá výhody reprezentace erodovaných objektů pomocí trojúhelníkových sítí a navrhuje řešení problémů, které vznikají v důsledku použití této datové struktury. Trojúhelníkové sítě se ukázaly být vhodnou datovou strukturou pro použití při simulaci eroze díky jejich adaptivitě a možnosti modelovat složité konkávní prvky scény. Použití trojúhelníkových sítí však přináší nové problémy, například problém vzniku nekonzistence sítě v důsledku silné eroze nebo problém simulace složitých scén složených z více materiálů. Tato práce zkoumá zmíněné problémy a navrhuje jejich možná řešení.ObhájenoErosion simulation is an important problem in the field of computer graphics. The most prominent erosion processes in nature are weathering and hydraulic erosion. Many methods address these problems but they are mostly based on height fields or volumetric data. Height fields do not allow the simulation of complex fully 3D scenes while the volumetric data have high memory requirements. This thesis explores the advantages of representing the eroded objects as triangular meshes and proposes solutions to problems that arise due to the use of this data structure. Triangular meshes prove to be an advantageous data structure for erosion simulations due to their adaptivity and the possibility to model complex concave features. However, the use of the triangular meshes brings new problems to the erosion simulation, such as the problem of creation of an inconsistency in the mesh due to heavy erosion or the problem of simulation of complex scenes composed of multiple materials. This thesis explores these problems and suggests possible solutions

Représentation, modélisation et génération procédurale de terrains

Slides disponiblesSoutenance oral (présentation + questions) disponible sur demandeThis PhD (entitled "Representation, modelisation and procedural generation of terrains") is related to movie and videogames digital content creation, especially natural scenes.Our work is dedicated to handle and to generate landscapes efficently. We propose a new model based on a construction tree inside which the user can handle parts of the terrain intuitively. We also present techniques to efficently visualize such model. Finally, we present a new algorithm for generating large-scale terrains exhibiting hierarchical structures based on their hydrographic networks: elevation is generated in a broad compliance to water-tansport principles without having to resort on costly hydraulic simulations.Cette thèse (qui a pour intitulé "Représentation, modélisation et génération procédurale de terrains") a pour cadre la génération de contenus numériques destinés aux films et aux jeux-vidéos, en particulier les scènes naturelles.Nos travaux visent à représenter et à générer des terrains. Nous proposons, en particulier, un nouveau modèle de représentation qui s'appuie sur un arbre de construction et qui va permettre à l'utilisateur de manipuler des morceaux de terrain de façon intuitive. Nous présentons également des techniques pour visualiser ce modèle avec un maximum d'efficacité. Enfin nous développons un nouvel algorithme de génération de terrains qui construit de très grands reliefs possédant des structures hiérarchiques découlant d'un réseau hydrographique : le relief généré est conforme aux grands principes d'écoulement des eaux sans avoir besoin d'utiliser de coûteuses simulations d'érosion hydrique

Modelos de simulación en tiempo real de sistemas granulares mediante autómatas celulares.

RESUMEN Las herramientas de formación basadas en simulación y realidad virtual se han convertido en las últimas décadas en una potente erramienta para la formación y el entrenamiento de multitud de tareas, especialmente aquéllas que conllevan un coste o un riesgo elevado.   Debido a las exigencias de este tipo de aplicaciones, los modelos dinámicos utilizados deben  reproducir el comportamiento del sistema simulado con suficiente realismo como para qu los hábitos adquiridos por los aprendices sean correctos. Además, deben ser suficientemente robustos y eficientes como para poder ejecutarse de forma interactiva en tiempo real.   Dentro del ámbito de la simulación de maquinaria pesada, los sistemas granulares y la interacción con el terreno (arena, grava, material granel, etc.) forman parte de las tareas  fundamentales que realiza el usuario. Sin embargo, como consecuencia de una metodología inadecuada, existe una deficiencia importante en los modelos existentes para simulación interactiva en tiempo real.   A lo largo de este trabajo se revisa la metodología de modelado utilizada habitualmente, y se desarrolla un conjunto de modelos dinámicos para la simulación de sistemas granulares.   Para conseguir modelos con un comportamiento suficientemente realista, se parte de estudios teóricos sobre el comportamiento de los sistemas granulares y la interacción con el suelo. A partir de estos estudios, y utilizando el modelo computacional de los Autómatas Celulares, se desarrolla un conjunto de modelos dinámicos que permiten la simulación interactiva de un sistema granular y una herramienta   Los modelos se validan  utilizando los trabajos teóricos anteriores, y se analiza el significado de los parámetros para permitir su ajuste en función del tipo de material que se desee simular.   Para conseguir una implementación eficiente de los modelos que permita la simulación en tiempo real, se analizan las propiedades estadísticas de la dinámica del sistema. Gracias a este análisis se consigue alcanzar un coste inferior a cuadrático respecto a las dimensiones del sistema simulado.   Se revisan las técnicas de representación gráfica existentes y se mejora la representación de las zonas de flujo por medio de l utilización de técnicas de multitextura programadas en el procesador gráfico. ______________________________________________________________________________________________The training tools based on simulation and virtual reality have become in recent decades into a powerful tool for education and training of many tasks, especially those that involve a cost or a high risk.   Due to the demands of such applications, the dynamic models have to reproduce the behavior of the system simulated with sufficient realism so that the habits acquired by trainees are correct. Furthermore, they must be sufficiently robust and efficient to be able to run interactively in real time. Within the scope of the simulation of heavy machinery, granular systems and the interaction with the ground (sand, gravel, bulk material, etc..) are part of the fundamental tasks performed by the user. However, as a result of inadequate methodology, there is a major deficiency in existing models for real-time interactive simulation. Throughout this work we review the modeling methodology used routinely, and developed a set of dynamic models for the simulation of granular systems. To obtain models with a sufficiently realistic behavior is part of theoretical studies on the behavior of granular systems and interaction with the ground. From these studies, and using the computational model of cellular automata, we develop a set of dynamic models that allow for interactive simulation of a granular system and a tool. The models are validated using the previous theoretical work, and discusses the significance of the parameters to allow adjustment of the type of material you want to simulate. To achieve an efficient implementation of the models to allow the simulation in real time, we analyze the statistical properties of the dynamics of the system. Thanks to this analysis we reach a cost of less than quadratic with respect to the dimensions of the simulated system. We review the existing techniques of graphic representation and improving the representation of the flow areas through the use of techniques multitextured programmed in the processor graph.

Simulating desert scenery

An algorithm for simulating wind-ripples and moving sand is extended by the detection of fixed objects. This permits us simulation and animation of sand interacting with objects like houses, highways, cactuses, etc. Sand is accumulated on the windward side of an obstacle and the sand relocation and wind-ripples formation is diminished on the leeward side. The wind shadow depends on the object’s geometry and the wind speed and direction. Sand tongues are formed as the result of the sand motion

Simulating desert scenery

An algorithm for simulating wind-ripples and moving sand is extended by the detection of fixed objects. This permits us simulation and animation of sand interacting with objects like houses, highways, cactuses, etc. Sand is accumulated on the windward side of an obstacle and the sand relocation and wind-ripples formation is diminished on the leeward side. The wind shadow depends on the object’s geometry and the wind speed and direction. Sand tongues are formed as the result of the sand motion