This paper presents a method taking global illumination into account in a ray tracing environment. A vector approach is introduced, which allows to deal with all the types of light paths and the directional properties of materials. Three types of vectors are defined: Direct Light Vectors associated to light sources, Indirect Light Vectors which correspond to light having been diffusely reflected at least once and Caustic Light Vectors which are associated to light rays emitted by sources and reflected and/or transmitted by specular surfaces. These vectors are estimated at a small number of points in the scene. A weighted interpolation between known values allows to reconstruct these vectors for the other points, with the help of a gradient computation for the indirect component. This approach also allows to take uniform area light sources (spherical, rectangular and circular) into account for all the types of vectors. Computed images are thus more accurate and no discretizing of the geometry of the scene is needed.

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International audienceApplication Service Providers (ASPs) are increasingly adopting the cloud computing paradigm to provision remotely available resources for their applications. In this context, the ability of cloud computing to provision resources on-demand in an elastic manner is of the utmost practical interest for them. As a consequence, the field of cloud computing has witnessed the development of a large amount of elasticity management solutions deeply rooted in works from distributed systems and grid computing research communities. This chapter presents some solutions that differ in their goals, in the actions they are able to perform and in their architectures. In this chapter, we provide an overview of the concept of cloud elasticity and propose a classification of the mechanisms and techniques employed to manage elasticity. We also use this classification as a common ground to study and compare elasticity management solutions

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