Cloudmaps from static ground-view video *

• A cloudmap represents the sunlight attenuation caused by passing clouds.
• A video of an outdoor scene is sufficient to estimate the cloudmap.
• Three approaches are proposed, each based on different geometric assumptions.
• It is possible to estimate a cloudmap even when the camera does not view the sky.
• It is not strictly necessary to directly estimate the scene geometry.

Cloud shadows dramatically affect the appearance of outdoor scenes. We describe three approaches that use video of cloud shadows to estimate a cloudmap, a spatio-temporal function that represents the clouds passing over the scene. Two of the methods make assumptions about the camera and/or scene geometry. The third method uses techniques from manifold learning and does not require such assumptions. None of the methods require directly viewing the clouds, but instead use the pattern of intensity changes caused by the cloud shadows. An accurate estimate of the cloudmap has potential applications in solar power estimation and forecasting, surveillance, and graphics. We present a quantitative evaluation of our methods on synthetic scenes and show qualitative results on real scenes. We also demonstrate the use of a cloudmap for foreground object detection and video editing.