Maud Lastic (VISTA team) will publicly defend her PhD thesis “Efficient visual simulation of volcanic phenomena” on Monday, July the 3rd at 2pm at LIX (amphithéâtre Sophie Germain). The defense will be in English.

Jury

• M. Eric PAQUETTE, Professor at École de technologie supérieure de Montréal, Reviewer
• M. Sylvain LEFEBVRE, Senior Researcher at Inria, Université de Lorraine, Reviewer
• Mme Maud MARCHAL, Professor at Université de Rennes, INSA/IRISA, Examiner
• M. Kiwon UM, Assistant Professor at Télécom Paris, Examiner
• M. Claude JAUPART, Professor at Université Paris Cité, Institut de Physique du Globe de Paris, Examiner
• Mme Marie-Paule CANI, Professor at École polytechnique, Thesis Director
• M. Damien ROHMER, Professor at École polytechnique, Thesis Co-director

Abstract

Offering tools to easily and efficiently create consistent natural phenomena is one of the main challenges in Computer Graphics, where visually plausible but controllable virtual effects are mandatory for 3D films, simulators and games.

The goal of this PhD is to propose novel multi-scale models for animating volcanic eruptions. These models are meant to be used by artists, giving several goals to achieve: being plausible, which means having a geometric resemblance to reality, as well as having the correct temporal dynamic; being fast in order to be able to be used interactively while permitting an usage in video games; and finally being controllable, with light and easy to understand model, so that users can easily adapt them to their needs.

To animate explosive eruptions, we propose a model that takes their unique dynamics into account, resulting into ascending plumes propagating upward and finally spreading side-way as well as pyroclastic flows spreading down the slopes of the volcano, depending on initial conditions. Our model combines two consistently coupled, simple sub-models: a minimalist Lagrangian simulation, used to represent dynamic horizontal slices of material ejected by the volcano and interacting with the surrounding air; and a procedural model that enhances the visual animation of the turbulent flow with multi-resolution details.

We extend this model by combining it with an atmospheric model, where several horizontal layers represent the atmosphere and we simulate the physical phenomena leading to the formation of clouds. Thus, several types of clouds can be animated and interact with a plume. Lastly, lava flows are among the most complex targeted phenomena, since they involve fluids evolving to a variety of behaviors while cooling down, from liquid to plastic, and then to rigid states. The visual aspect of lava is often hybrid, with liquid parts carrying cooler elements, and deformable crust that folds and deforms. None of these methods was able to handle the interaction between the visual state of the lava and the underlying flow, nor the formation and folding of deformable surface sheets. Therefore, rather than tackling pure simulation, we use as a base an existing Eulerian simulation of lava flows and build a geometrical simulation of the surface of the flow, letting folds appear knowing the velocity and temperature of the flow. We texture the flow using time-consistent textures generated according to the thickness of the crust.