Spectral Measurement and Data Processing of Textile Surface Reflection

This paper reports a study on reflection measurement of a textile surface. The measurement was made involving spatial directions and wavelength. To integrate a spectral detector with a setup for different lighting and viewing directions, the method of fixed sample normal is proposed. In this method, the sample's surface normal is fixed and various lighting and viewing directions are obtained by relocating the source and detector. A visualization system was developed to help explore the measured data. The system allows the user to select a measured data point to display simultaneously the spectrum and its associated color and angle information. Finally, a new interpolation method based on space partition was proposed. Given an interpolation point P, the space is subdivided into subspaces and the data point closest to P in each subspace is selected. This generates a set of points and tetrahedrons, and if any tetrahedron contains P, it will be used for the interpolation based on the barycentric coordinates. This study is useful for multiple applications such as realistic image synthesis, verification of reflection models, and investigation of the relationships between textile appearances and the underlying physical parameters.