LightTools 6.1 illumination design and analysis software from Optical Research Associates provides advanced features for the design of luminaires, LEDs and displays. The package includes the Ray Path function for identifying system elements that contribute to light loss, scatter, unintentional reflections or ghost images. It enables the application of measured bidirectional scattering distribution function (BSDF) data (isotropic and anisotropic) to a surface for accurately modeling scattering surfaces. A library of BSDF data of reflective materials used in luminaire construction is included. Among other additions are tools for gradient index lenses, methods to specify the properties of phosphors and expanded foreign language support.