Bi-polynomial Modeling of Low-frequency Reflectances.

We present a bi-polynomial reflectance model that can precisely represent the low-frequency component of reflectance. Most existing reflectance models aim at accurately representing the complete reflectance domain for photo-realistic rendering purposes. In contrast, our bi-polynomial model is developed for the purpose of accurately solving inverse problems by effectively discarding the high-frequency component while retaining nonlinear variations in the low-frequency part. The bi-polynomial reflectance model is useful for estimating reflectance and shape of an object. Experimental evaluation in comparison with other parametric reflectance models demonstrates that the proposed model achieves better performance in reflectometry and photometric stereo applications.