Webcam Clip Art:
Appearance and Illuminant Transfer
from Time-lapse Sequences


We introduce a new, high-quality dataset of calibrated time-lapse sequences (a). Illumination conditions are estimated in a physically-consistent way and HDR environment maps are generated for each image (b). This database can be used as a ``clip art'' library for applications like inserting lighting-consistent 2D objects, such as the buildings in (c), or relighting 3D objects, such as the statue in (d).



Calibrated webcams

Webcams placed all over the world observe and record the visual appearance of a variety of outdoor scenes over long periods of time. The recorded time-lapse image sequences cover a wide range of illumination and weather conditions -- a vast untapped resource for creating visual realism. In this work, we propose to use a large repository of webcams as a "clip art" library from which users may transfer scene appearance (objects, scene backdrops, outdoor illumination) into their own time-lapse sequences or even single photographs. The goal is to combine the recent ideas from data-driven appearance transfer techniques with a general and theoretically-grounded physically-based illumination model. To accomplish this, the paper presents three main research contributions: 1) a new, high-quality outdoor webcam database that has been calibrated radiometrically and geometrically; 2) a novel approach for matching illuminations across different scenes based on the estimation of the properties of natural illuminants (sun, sky, weather and clouds), the camera geometry, and illumination-dependent scene features; 3) a new algorithm for generating physically plausible high dynamic range environment maps for each frame in a webcam sequence.


Paper thumbnail Jean-Fran├žois Lalonde, Alexei A. Efros, and Srinivasa G. Narasimhan. Webcam Clip Art: Appearance and Illuminant Transfer from Time-lapse Sequences, ACM Transactions on Graphics (SIGGRAPH Asia 2009), 28(5), 2009. [PDF] [BibTeX]


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