IGI: BRDF from Direct Illumination
	Li = (ρd/π + ρsK(α,Θi))Ii Li is the radiance Ii is the irradiance ρd/π is the diffuse term ρsK(α,Θi) is the specular term α is the parameterized surface roughness Θi is the azimuth of the incident and viewing directions § The data from the images collected we can solve the nonlinear optimization problem and get parameters for ρs, ρd and α § The radiance image must cover an area with a specular highlight or we will not have enough information for recovering the specular parameters.