Erm.. actually, I was just re-iterating what you said above about this being a partial-solution that may or may not be appropriate for each case.  I guess you could just fine-tune the angle by hand for exceptions... so I was mostly asking if you had enough info/node-control to base it on the (main? brightest? total?) light-source.

[EDIT: cross-posted.. this comment was not meant in response to ice-boy]

[EDIT #2: Hmm... lambert-shaded AO maybe? ;) ]

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