What happens if the position of a directional light is a not a unit vector? Are results for parallel vector directional lights positions the same?
What happens if the position of a directional light is a not a unit vector?
Then the lighting computation will not produce reasonable output.
Are results for parallel vector directional lights positions the same?
No. Two lights can have different colors or other parameters. But if the two lights are identical in every way, then the result will be like one brighter light.
I vaguely recall, some people wrote this feature was exploited somehow by some. I suppose, non-unit position also makes the directional light brighter. Also, do the GL specs say something about non-unit directional light positions and where?