This implies among other things that the irradiance can be approximated using only 9 parameters, i.e. as a quadratic polynomial of the cartesian components of the surface normal, and that only the first 9 coefficients of the lighting can be recovered from a Lambertian object. Thereby, we show that if reciprocity of the BRDF is assumed, the light field can be factored up to global scale. New Practical Representations and Algorithms Insights from the theory lead to the derivation of a simple practical representation, which can be used to estimate BRDFs under complex lighting. Therefore, we can recover BRDFs under general, unknown lighting conditions. The images on the right with corresponding captions illustrate some of our results.
More information is found in the paper.
We expect the theoretical results, particularly the formalization of reflection as a convolution, to have broad impact in a number of areas in computer graphics and vision. This paper discusses just one of those areas, i.e. inverse rendering. Some of the companion papers below go into more depth in other areas such as forward rendering. The results are also likely to be of broad interest in computer vision. This may be simpler to read since it involves Fourier transforms rather than spherical harmonics and has most of the key insights.