Jason Scheuerman wrote:
> 
> I've been trying to figure out how to create a scene in which there is a
> light shining through a white linen cloth. For example, if you were to
> take a white bedsheet and hold it up near a lightbulb, you wouldn't see
> the exact outline of the bulb but you would see the light being
> dispersed through the sheet in a fuzzy outline.  (Am I making myself
> clear?)  Anyone know how to accoplish this in POV?
> 
> Jason Scheuerman
> mt### [at] nullnet


I would suggest trying to do this texturaly. It will be difficult
to get the material properties correct to allow light to pass
in one spot only without effecting the rest of the object.

Try something like a spotted pigment with a sloped color. By that
I mean if the sheet is to be white with the spot of light in the
middle you could make the first part of the color map white and
then change the entries color intensities slowly towards the end
of the map. If this method is used you will need to scale the
pigment large enough that it only covers the object once and will
have experiment to find the correct translations and finishes.

 Below is a totaly untested and incomplete example of a sloped
color map entry:

#declare Sheet_Pigment =
 pigment{
  spotted
   color_map{
   [.750 rgb<.900,.900,.900>]
   [.750 rgb<.900,.900,.900>]
   [.791 rgb<.916,.916,.916>]
   [.833 rgb<.933,.933,.933>]
   [.875 rgb<.950,.950,.950>]
   [.916 rgb<.966,.966,.966>]
   [.958 rgb<.983,.983,.983>]
   [1.00 rgb<1.00,1.00,1.00>]
  }
}

The above gives a slow ramp from very light gray
to white.

 There are some other things yuo can do to the above
to increase the look of the effect. By leaving the
blue component at .9 and increasing the red and green
equaly you will have it change slowly to a very light
yellow color towards the center of the spot. The
following example shows how you can phase from white
to light yellow and change the intensity of the spot
colors without changing the shade of the colors
choosen:

#declare Sheet_Pigment =
 pigment{
  spotted
   color_map{
   [.750 rgb<.900,.900,.900>*1.00]
   [.750 rgb<.900,.900,.900>*1.05]
   [.791 rgb<.916,.916,.900>*1.10]
   [.833 rgb<.933,.933,.900>*1.15]
   [.875 rgb<.950,.950,.900>*1.20]
   [.916 rgb<.966,.966,.900>*1.25]
   [.958 rgb<.983,.983,.900>*1.30]
   [1.00 rgb<1.00,1.00,9.00>*1.35]
  }
}


Again this is untested and a different pigment type may
be needed but it gives you something to start with.

Good luck !

-- 
Ken Tyler

tyl### [at] pacbellnet

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