Simulation et rendu temps-réel de nuages convectifs à l'échelle du paysage

This paper presents an efficient, physics-based procedural model for the real-time animation andvisualization of cumulus clouds at landscape size.We couple a coarse Lagrangian model of air parcels with a proceduralamplification using volumetric noise.Our Lagrangian model draws an aerology \ie the atmospheric physicsof hydrostatic atmosphere with thermodynamics transforms,augmented by a model of mixing between parcels and environment.In addition to the particle-particle interactions, we introduce particle-implicit environmentinteractions. In contrast to the usual fluid simulation, we thus do not needto sample the transparent environment, a key property forreal-time efficiency and scalability to large domains.Inheriting from the high-level physics of aerology, we also validate oursimulation by comparing it to predictive diagrams, and we show how the user caneasily control key aspects of the result such as the cloud base andtop altitude. Our model is thus fast, physical and controllable.Cet article présente un modèle temps-réel procédural basé sur laphysique pour l'animation et la visualisation temps réel de cumulus à l'échelle du paysage. Nous couplons un modèle Lagrangien basse-résolution de parcelles atmosphériques avec un modèle d'amplification procédurale à base de bruit volumique.Notre modèle Lagrangien s'appuie sur l'aérologie \ie la physique de l'atmosphère en équilibre hydrostatique avec transformations thermodynamiques,augmentée d'un modèle de mélange entre les parcelles et de l'environnement.En plus des interactions entre particules, nous introduisons lesinteractions entre les particules et l'environnement implicites. Contrairement à la simulation de fluides habituel, on n'a donc pas besoin d'échantillonner l'environnement transparent, une propriété clé pourl'accessibilité au temps réel et la scalabilité aux grandes étendues.Héritant de la physique à haut niveau de l'aérologie, nous validons notresimulation en la comparant aux diagrammes prédictifs, et nous montrons comment l'utilisateur peutcontrôler facilement les principaux aspects du résultat commel'altitude de la base et du haut des nuages. Notre modèle est donc rapide, physique et contrôlable

Atmospheric cloud representation methods in computer graphics: A review

Cloud representation is one of the important components in the atmospheric cloud visualization system. Lack of review papers on the cloud representation methods available in the area of computer graphics has directed towards the difficulty for researchers to understand the appropriate solutions. Therefore, this paper aims to provide a comprehensive review of the atmospheric cloud representation methods that have been proposed in the computer graphics domain, involving the classical and the current state-of-the-art approaches. The reviewing process was conducted by searching, selecting, and analyzing the prominent articles collected from online digital libraries and search engines. We highlighted the taxonomic classification of the existing cloud representation methods in solving the atmospheric cloud-related problems. Finally, research issues and directions in the area of cloud representations and visualization have been discussed. This review would be significantly beneficial for researchers to clearly understand the general picture of the existing methods and thus helping them in choosing the best-suited approach for their future research and development

Simulación de nubes volumétricas

Simular una atmósfera realista supone tener en cuenta un fenómeno que podemos vercasi cada día en el cielo: las nubes. Este fenómeno compuesto de partículas de agua y/ohielo puede parecer fácil de representar, pero esconde una geometría fractal que lo com-plica. Por esto mismo, a lo largo de los años han surgido diferentes estudios que tratan deencontrar un modelo para ello. Además, otra parte importante de estas es su iluminación:cuando un rayo de luz atraviesa una nube, los fotones que componen la primera pueden serdispersados o absorbidos por las partículas de la segunda. Simular este comportamiento esuna tarea difícil.En este trabajo de fin de grado se va a estudiar una de las técnicas que existen para lasimulación de nubes volumétricas. En el modelo estudiado se utilizan varias texturas 2D y3D creadas mediante ruido procedural (Perlin y Worley). Estas texturas se utilizan paradefinir dónde, con qué forma y detalle se van a mostrar las nubes. Para visualizarlas seutiliza un algoritmo llamadoray marchingque calcula la densidad e iluminación de la nubepor cada iteración. En el caso de la iluminación, se utilizan dos funciones para aproximarla:la ley de Beer y la función de fase de Henyey-Greenstein.Además, se ha implementado una aplicación que permite visualizar nubes, permitiendocambiar la cantidad que hay en el cielo, su densidad, la altura a la que se encuentran, suiluminación o la posición del sol. También es posible hacer que estas se muevan en unadirección y con una velocidad fijada

Real-time landscape-size convective clouds simulation and rendering

International audienceThis paper presents an efficient, physics-based procedural model for the real-time animation and visualization of cumulus clouds at landscape size. We couple a coarse Lagrangian model of air parcels with a procedural amplification using volumetric noise. Our Lagrangian model draws an aerology i.e., the atmospheric physics of hydrostatic atmosphere with thermodynamics transforms, augmented by a model of mixing between parcels and environment. In addition to the particle-particle interactions, we introduce particle-implicit environment interactions. In contrast to the usual fluid simulation, we thus do not need to sample the transparent environment, a key property for real-time efficiency and scalability to large domains. Inheriting from the highlevel physics of aerology, we also validate our simulation by comparing it to predictive diagrams, and we show how the user can easily control key aspects of the result such as the cloud base and top altitude. Our model is thus fast, physical and controllable

Real-time landscape-size convective clouds simulation and rendering

This paper presents an efficient, physics-based procedural model for the real-time animation and visualization of cumulusclouds at landscape size. We couple a coarse Lagrangian model ofair parcelswith a procedural amplification using volumetricnoise. Our Lagrangian model draws an aerologyi.e.,the atmospheric physics of hydrostatic atmosphere with thermodynamicstransforms, augmented by a model of mixing between parcels and environment. In addition to the particle-particle interactions,we introduce particle-implicit environment interactions. In contrast to the usual fluid simulation, we thus do not need to samplethe transparent environment, a key property for real-time efficiency and scalability to large domains. Inheriting from the high-level physics of aerology, we also validate our simulation by comparing it to predictive diagrams, and we show how the user caneasily control key aspects of the result such as the cloud base and top altitude. Our model is thus fast, physical and controllable