Sujet de Master 2008-2009
Simulating an evolving cloudy sky
/ Simuler un ciel nuageux évolutif


Fabrice NEYRET -   équipe AERIS(ARTIS), LJK, à l'INRIA-Montbonnot


Weather simulations (low resolution) as well as physical simulations of isolated clouds are very expensive, and still, approximate and unable to produce detailed realistic skies. In the context of graphics applications (video games, simulators, google earth -like exploration), one also wants real-time performance, exploration of wide areas, but also control (i.e., predictability) of the result by the graphist !
Fortunately, the cloud physics is not limited to the numerical solving of differential equations (Navier-Stokes): aerodroms and pilots have simple methods for evaluating the key parameters (instability, cloud base and top height). Moreover, several stereotypical "patterns" rule phenomena (frontology, inversions, aerothermy due to topography and soil type, ribbons and convective cells) ... Conversely, there exist many CG methods able to combine computer simulation and coarse procedural enrichment, and to generate or regenerate on the fly parameters required for a portion of landscape. Thus, past or ongoing works in our lab concern the coupling of models of different scales, the procedural simulation of fluids, the real-time exploration of vast landscapes, rendering real-time clouds.


The aim of this study is to simulate plausibly and in real-time a cloudy sky on a landscape portion (depending on the exploration), seen from ground or above (as a first step we can focus on cumuluniform clouds seen from not far). To be able to regenerate any portion of the sky on demand and to adapt to the needed resolution, the idea is to couple coarse physical simulation and proceduralism, and to adopt a multi-scale strategy. The ingredients are: the atmospheric 3D environment (state, movements), the thermals emitted from the ground which moisture creates clouds when condensing, and the soil environment which modulates the emission of thermals and air movements.

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