Filename format
Due to compatibility reasons the filename format follows BTF Database Bonn (but any other angular resolution can be measured if required); i.e. the illumination and viewing directions are specified by spherical angles Θl (tl), Φl (pl), Θv (tv), and Φv (pv).
Each angle is specified by three digit integer values in degrees.
Filename example: tl000_pl000_tv000_pv000.png(.exr)
Images of individual view directions are stored in dedicated directories named by viewing angles: e.g. ./tv000_pv000/
Illumination and vieving directions sampling
The initial measurements use the same angular sampling as measurements of BTF database Bonn; i.e. 81 x 81 illumination and viewing directions uniformly distributed over hemisphere above the sample:
A list of individual directions is available (individual columns represent: direction number, angle Θ, angle Φ, angle ΘlS, angle ΦlS). Note that for such combinations of illumination and view directions where camera and light positions is identical (Θl==Θv && Φl==Φv), the light position should be shifted to ΘlS and ΦlS.
Routines generating list of Θ and Φ angles are available for MATLAB and C++.
Image format
Individual BTF images are stored either in PNG format (colour space sRGB 8-bits/channel) or in HDR OpenEXR (colour space XYZ (illum. D65) half-float/channel). The format may vary across the BTF samples so check information about each sample in the download section.