Paris, Axel2023-09-252023-09-252023-03-21https://diglib.eg.org:443/handle/10.2312/3543881This PhD, entitled "Modeling and simulating virtual terrains" is related to digital content creation and geological simulations, in the context of virtual terrains. Real terrains exhibit landforms of different scales (namely microscale, mesoscale, and macroscale), formed by multiple interconnected physical processes operating at various temporal and spatial scales. On a computer, landforms are usually represented by elevation models, but features such as arches and caves require a volumetric representation. The increasing needs for realism and larger worlds bring new challenges that existing techniques do not fulfill. This thesis is organized in two parts. First, we observe that several macroscale landforms, such as desert landscapes made of sand dunes and meandering rivers, simply cannot be modeled by existing techniques. Thus, we develop new simulations, inspired by research in geomorphology, to generate these landforms. We particularly focus on the plausibility of our results and user control, which is a key requirement in Computer Graphics. In the second part, we address the modeling and generation of volumetric landforms in virtual terrains. Existing models are often based on voxels and have a high memory impact, which forbids their use at a large-scale. Instead, we develop a new model based on signed distance functions for representing volumetric landforms, such as arches, overhangs and caves with a low memory footprint. We show that this representation is adapted to generating volumetric landforms across a range of scales (microscale, mesoscale, and macroscale).enterrain modelsprocedural modelingphysical simulationsimplicit surfacesThesis