Re: [Plib-users] Shadow
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sjbaker
From: <Ran...@ma...> - 2001-02-18 22:21:53
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http://geography.bu.edu/brdf/brdfexpl.html I think the misunderstanding is because I didn't really make clear that I am talking about the amount of illumination perceived by the eye across the whole field of view. As a thought experiment, place yourself on the line joining the sun and the plate. Notionally pick a spot behind the plate to target your eyes on. Initially *no* shadow will be visible around the plate ("the sun sees no shadows"). Now move away from the line. As you move away, you see more and more shadow. This effect integrated across all the shadow casting things gives the *apparent* increase in brightness. What is really happening is that you are merely seeing less shadow around the shadow cast by the observer. If you want to dispense with the shadow cast by the observer (say the sun is doing the observation), that's ok. It still works. The web-page explains it much better than I do/did. My apologies for the confusion, it wasn't intended. If a means of generating the phenomenon exists which is not too hard and not very CPU intensive exists, it would be worth it. It is one of those things that makes "synthetic" images look really flat at lifeless (unless you are simulating an overcast day). Randall |