The lights.rad file must be in the same directory as qrad.exe. You can specify the brightness in the red, green, and blue spectrums. Higher numbers result in lower quality lighting but can speed up the testing process. This helps reduce the number of surfaces effected by any given switchable light. Helps reduce stair stepping effect along the edges of shadows.
Higher values result in more contrast and light intensities being cut off sooner.
Qrad will look for lights.rad by defaut in the directory that qrad.exe is run from. This turns that off. Set to 0 for direct light only. Copyright 1996-2000, All rights reserved. Site Content Copyright Valve, LLC 1998-2000, unless otherwise specified.