The problem of estimating an illumination distribution from images is called inverse lighting. For inverse lighting, three approaches have been developed based on specular reflection components, diffuse reflection components, and cast shadows. The present study provides theoretical insights as to why the approach based on cast shadows works in a reliable manner, and discusses what kind of basis functions are appropriate to be used for recovering illumination from cast shadows. First, we formalize the approach based on cast shadows by using spherical harmonics. Then, we analyze the approach in the frequency domain and show the advantages and the limitations of the approach. Second, motivated by the observations in the frequency domain, we propose an efficient method using Haar wavelets that provide compact supports and sparsity of coefficients. Finally, we report the results of experiments that compared the method using spherical harmonics and the method using Haar wavelets.
Spherical harmonics vs. Haar wavelets: basis for recovering illumination from cast shadows
2004-01-01
367561 byte
Aufsatz (Konferenz)
Elektronische Ressource
Englisch
Spherical Harmonics vs. Haar Wavelets: Basis for Recovering Illumination from Cast Shadows
British Library Conference Proceedings | 2004
|Stability Issues in Recovering Illumination Distribution from Brightness in Shadows
British Library Conference Proceedings | 2001
|Detailanalyse des Hirndrucks mit HAAR-Wavelets
British Library Online Contents | 2008
WASHINGTON WATCH - Budget woes cast wide shadows.
Online Contents | 2006