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The intensity varies between 0 and 1, where 0 is extreme dark and 1 is full brightness. This intensity range may be restricted to less extreme values with theQBRIGHT command, by which minimum Bl and maximum Bh intensities may be set by cell, material, or density. The brightness levels alter the intensity by
I = Bl + I0 ( Bh - Bl )where I0 is the original intensity as given by the cos(A) formula. This modification restricts the number of shades (where used) of a basic color used for the zone(s) affected, i.e., a new set of NShade shades within the allowed brightness levels is NOT calculated. Setting Bl > 0 is useful for highlighting a particular cell or material and for preventing objects in shadows to be totally black. Color intensities I > 0.3 appear rather dark with the default gamma correction; QBRIGHT may be used to prevent a cell or material from becoming too dark. QBRIGHT is also useful for setting a minimum intensity for black and white. The default dark black is white, and dark any color is always black. QBRIGHT may be used to keep black from being white and to keep white from being black.
A minimum brightness may be set for all colors with QPALET SET MINBRIGHTNESS. A value of 0 gives the default setting of near black as the darkest shade. A value of 0.2 prevents very dark shades while still providing a good range of shades. Unlike with the QBRIGHT settings, the full number of intensity levels is used.