"' Directional-hemispherical reflectance "'is the reflectance of a surface under direct illumination ( with no diffuse component ).
12.
While the direct illumination is generally best sampled using eye-based ray tracing, certain indirect effects can benefit from rays generated from the lights.
13.
Like the O'Neill cylinder, McKendree proposed dedicating half of the surface of the colony to windows, allowing direct illumination of the interior.
14.
In fluorescence microscopy, dichroic filters are used as beam splitters to direct illumination of an excitation frequency toward the sample and then at an analyzer to reject that same excitation frequency but pass a particular emission frequency.
15.
Unlike the Belt of Venus, the direct illumination of clouds and aerosols that create the afterglow which characterizes alpenglow hover low in the atmosphere and create a red horizontal band visible just after sunset or before sunrise.
16.
The area subjected to direct illumination is almost exactly half the planet; but because of atmospheric and other effects that extend the reach of indirect illumination, the area of the planet covered by either direct or indirect illumination amounts to slightly more than half the surface.
17.
Such algorithms take into account not only the light that comes directly from a light source ( " direct illumination " ), but also subsequent cases in which light rays from the same source are reflected by other surfaces in the scene, whether reflective or not ( " indirect illumination " ).
