Playable Environments: {V}ideo Manipulation in Space and Time

We present Playable Environments-a new representation for interactive video generation and manipulation in space and time. With a single image at inference time, our novel framework allows the user to move objects in 3D while generating a video by providing a sequence of desired actions. The actions are learnt in an unsupervised manner. The camera can be controlled to get the desired viewpoint. Our method builds an environment state for each frame, which can be manipulated by our proposed action mod-ule and decoded back to the image space with volumetric rendering. To support diverse appearances of objects, we extend neural radiance fields with style-based modulation. Our method trains on a collection of various monocular videos requiring only the estimated camera parameters and 2D object locations. To set a challenging benchmark, we in-troduce two large scale video datasets with significant cam-era movements. As evidenced by our experiments, playable environments enable several creative applications not at-tainable by prior video synthesis works, including playable 3D video generation, stylization and manipulation 1 1 willi-menapace.github.io/playable-environments-website

On the role of the mesoscale circulation on an idealized coastal upwelling ecosystem

International audienceAn idealized circulation model of coastal upwelling coupled to an ecosystem model has been built to address the impact of features such as eddies and filaments emerging from mesoscale dynamics on a marine ecosystem. The model mimics coastal upwelling along an infinite straight coast with north-south cyclic boundary conditions. Thanks to the parametrization of the geostrophic onshore flow in the thermocline, the circulation captures the typical characteristics of a coastal upwelling region: an equatorward coastal jet, a poleward undercurrent along the continental slope and mesoscale eddies and filaments. This eddying three-dimensional simulation is compared to a two-dimensional simulation using the averaged velocity field of the first simulation as velocity field. This approach allows us to compare simulations having similar upwelling and nutrient input but differing in the nature of the flow. An offshore spreading of the phytoplankton bloom is found in the eddying simulation. The width of the productive coastal band is increased from 80 km to 200 km by the mesoscale activity. A biogeochemical budget carried out in a 300 km-wide coastal band provides evidence that mesoscale activity decreases the total phytoplankton content mainly by exporting a significant part of the surface phytoplankton below the euphotic layer. In presence of mesoscale activity, the downward and offshore export of phytoplankton, zooplankton and detritus significantly contributes to total export of organic matter out of the surface coastal ocean, whereas their contribution to export is weak in the two-dimensional case