Practical Image-Based Relighting and Editing with <br>Spherical-Harmonics and Local Lights
Practical Image-Based Relighting and Editing with
Spherical-Harmonics and Local Lights
CVMP 2011
Borom Tunwattanapong   Abhijeet Ghosh   Paul Debevec
USC Institute for Creative Technologies

Face relighting comparison under the Grace cathedral environment (a). (b) 20 SH lights. (c) 20 local lights. (d) Our proposed technique for combining SH lighting with local lights (20 lighting conditions). (e) Ground truth image-based relighting consisting of 156 lights.



We present a practical technique for image-based relighting under environmental illumination which greatly reduces the number of required photographs compared to traditional techniques, while still achieving high quality editable relighting results. The proposed method employs an optimization procedure to combine spherical harmonics, a global lighting basis, with a set of local lights. Our choice of lighting basis captures both low and high frequency components of typical surface reflectance functions while generating close approximations to the ground truth with an order of magnitude less data. This technique benefits the acquisition process by reducing the number of required photographs, while simplifying the modification of reflectance data and enabling artistic lighting edits for post-production effects. Here, we demonstrate two desirable lighting edits, modifying light intensity and angular width, employing the proposed lighting basis.



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