> Lars W. wrote:
> > 
> > Hi
> > 
> > I am trying to combine real Images, and POV-Images, and for that i need
> > to know
> > how to create Objects, that make shadows, but are not seen, i mean they
> > must be
> > 100 % transparent, but the shadows must be dark.
> > 
> > Does anybody know if such things are possible with POV-Ray ?
> > or maybe knows some alternatives ?

	One idea: if you have one predominant light-source, put a very, very tiny 
version of your object [sub-pixel-sized] very close to it.  As the light
source is a point, a .01mm object .02mm away from the light will cast just
as good a shadow as a 1m object 2m away. This has the advantage that it
allows an actual POVthing to cast a shadow w/o being seen. It won't work if
there are several strong light sources, unless you get the proportions and
positions just right.
(If you *do*, though, there is no reason that you could not get [say] a
human figure that appears only by casting *correct* shadows in several
intersecting spotlights. Spooky!) I don't think it will work at all with
linear or area lights.

	Another possibility is to create a darklight [=negative intensity light
source] in a "magic lantern" [= opaque box with a shaped cutout or
transparent "dianegative"] and, again, shrink it to speck size. With this,
I imagine that you could even cast colored shadows [think a shadow with
colored eyes?]  This will work against any available light but has the
disadvantage that it may interact oddly with other shadows - it may look
more like a dark stain than a shadow, as it will interact independly with
shadows from every source.

	-Robert Dawson

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