Master 2008-2009
Real-time rendering of Earth-scale clouds

Advisor

Eric Bruneton
LJK/EVASION

Context

The research work about terrain modeling and rendering at Evasion.

Description

Recently several applications allowing users to view the Earth at all scales have appeared, like Google Earth. In order to increase the realism of these applications it is necessary to render the atmosphere ([Bruneton 08]). And since the atmosphere always contains clous, at least at large scales, a realistic rendering requires also to render clouds.

Many methods have been proposed to render clouds in real-time ([Gardner 85], [Nishita 96], [Harris 01], [Riley 04], [Bouthors 06], [Bouthors 08], etc), but most of them are designed for a ground observer, which therefore sees a "limited" number of clouds. [Dobashi 06] is an exception since they handle clouds at the scale of the Earth. But they are only interested in the animation of clouds, not in their real-time realistic rendering.

In this context the goal is to propose and study extensions to the cloud rendering method of [Bouthors 06], in order to handle Earth-scale clouds. In particular the radiosity algorithm for the clouds-ground inter-reflections will need to be improved, so as to remove the limitations to flat grounds (by using the results of [Vidal 08] in order to know which physical effects can be neglected or not). The proposed method should be compatible with cloud animations, even if the animation itself is out of the scope of this Master. It will also be necessary to adapt the method to the multi-resolution algorithms that are used and needed to handle data sets that do not fit in main memory (clouds cover texture, ground reflectance texture, etc). The proposed method will be evaluated by integrating it in the terrain rendering software of EVASION, which can render the whole Earth at all scales, but with currently unrealistic clouds ([Bruneton 08]).

References

[Bouthors 06] Real-time realistic illumination and shading of stratiform clouds
Bouthors A., Neyret F., Lefebvre S., EGWNP 06

[Bouthors 08] Interactive multiple anisotropic scattering in clouds
Bouthors A., Neyret F., Max N., Bruneton E., Crassin C., I3D 08

[Bruneton 08] Precomputed Atmospheric Scattering
Bruneton E., Neyret F., EGSR 08

[Gardner 85] Visual simulation of clouds
Gardner G. Y., SIGGRAPH 85

[Harris 01] Real-time cloud rendering
Harris M. J., Lastra A., Eurographics 01

[Nishita 96] Display of clouds taking into account multiple anisotropic scattering and sky light
Nishita T., Nakamae E., Dobashi Y., SIGGRAPH 96

[Riley 04] Efficient rendering of atmospheric phenomena
Riley K., Ebert D. S., Kraus M., Tessendorf J., Hansen C., EGSR 04

[Vidal 08] Illumination réaliste de terrains en temps-réel
Vidal V., Rapport de Master 2