For improved multispectral classification and retrieval of Lambertian reflectances from patches of arbitrary surface orientation, we investigate the consequences of a dichromatic illumination model accounting for direct sunlight and diffuse skylight. This illumination model leads to the concept of spectral classes as two dimensional planes in the feature space. This paper addresses three questi...

Sunlight and skylight are rarely rendered correctly in computer graphics. A major reason for this is high computational expense. Another is that precise atmospheric data is rarely available. We present an inexpensive analytic model that approximates full spectrum daylight for various atmospheric conditions. These conditions are parameterized using terms that users can either measure or estimate...