在本論文中，我們利用立體光度測量(photometric stereo)從真實場景的時移影片(time-lapse video)推算出幾何的光度特性。一般而言，立體光度測量(photometric stereo)大都用來取得室內小型物體的三維模型，或是材質樣本，但透過取得的天空時移影像，我們可以計算出戶外場景建築物上的反射度(reflectance)和表面法線(surface normal)。而從天空的時移影像中，我們可以得到大自然的環境光和太陽的資訊。在本文的最後我們會用重建出來的時移影片(photometric stereo)來證明這些光影性質。

In this paper, we use photometric stereo to estimate geometric and photometric properties of real scenes from time-lapse videos. In general photometric stereo is used to obtain 3D model for small objects or material samples with indoor scenes. By collecting the sky video of the time-lapse video, we can obtain reflectance and surface normal on building of natural lighting outdoor scenes. From the sky video, the natural lighting environments, and sun information are obtained Applications of the reconstruction of the time-lapse video are also demonstrated.

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