<title>Comparison of measured BRDF data with parameterized reflectance models</title>

Scene simulation has proved to be a valuable tool for analysing the images perceived by visible and infrared imaging systems. Accurate scene simulation requires accurate incorporation of the optical properties of all the materials within a scene, with reflectance incorporated with the bidirectional reflectance distribution function (BRDF) and emission incorporated through the directional emissivity or hemispherical directional reflectance (HDR). This paper compares the fit of various parameterised models to experimental BRDF data from a variety of surfaces representing the extremes of material properties found in the environment. One of the main aims is to infer the accuracy and validity of an in-house BRDF model called Mopaf using data representative of different sorts of isotropically reflecting materials. Where appropriate physical and semiempirical models and a novel parameter based BRDF model were compared with Mopaf and with BRDF data from a Surface Optics Corporation SOC-200 instrument. It was concluded that Mopaf might not be reliable for all the angular BRDF data, especially specularly reflecting surfaces or grazing incidence data. Likewise, the other BRDF models investigated tended to be limited to a range of physical conditions such as only diffuse reflection or to a range of surface roughness. It was shown that the proposed new BRDF model was more generally applicable from the visible to infrared wavelengths, over a wide range of reflection angles and for different sorts of surface material.