The bidirectional reflectance distribution function, symbol f r, is a function of four real variables that defines how light from a source is reflected off an opaque surface. It is employed in the opt
The final BRDF is the aggregated effect of the geometry and ink selection.
Opposition surge
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The opposition surge is the brightening of a rough surface, or an object with many particles, when illuminated from directly behind the observer. The term is most widely used in astronomy, where gener
Bidirectional reflectance distribution function
…Lambertian model, representing perfectly diffuse (matte) surfaces by a constant BRDF. Lommel–Seeliger, lunar and Martian reflection. Hapke scattering model, physically motivated approximation of the radiative transfer solution for a porous, irregular…
Opposition surge from the retroreflective lunar soil brightens the area around Buzz Aldrin's shadow during Apollo 11 (photo by Neil Armstrong).