"gvdeynde" <gvd### [at] hotmailcom> wrote in message
news:433c3135$1@news.povray.org...
> Hi,
>
> Scene: one spotlight, one coloured glass ball (photon target on for
> reflection and refraction, collect off), white plane below ball; setting up
> photons only using spacing and autostop. Povray 3.6.1 for windows.
>
> Without photons enabled: a coloured shadow from the glass ball
> With photons: some caustics, but the coloured shadow has become grey.
>
> Is this normal behaviour? Why would the colour disappear?

this is normal behaviour, and it's the realistic thing to happen, although you
might expect otherwise.  But just try it: fill a glass with a coloured but
transparent fluid, for example ice-tea, and shine a light through it.  Now look
at the shadow of the glass, you will notice that it's mostly just dark,
uncoloured shadow and only the caustics have some of the colour of the fluid.

After that, you can enjoy a nice glass of ice tea to celebrate the newly learned
facts about light and shadow! :p

cu!
--
#macro G(b,e)b+(e-b)*C/50#end#macro _(b,e,k,l)#local C=0;#while(C<50)
sphere{G(b,e)+3*z.1pigment{rgb G(k,l)}finish{ambient 1}}#local C=C+1;
#end#end _(y-x,y,x,x+y)_(y,-x-y,x+y,y)_(-x-y,-y,y,y+z)_(-y,y,y+z,x+y)
_(0x+y.5+y/2x)_(0x-y.5+y/2x)            // ZK http://www.povplace.com

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