Two posts in a row!  Anyhow, forgive my ignorance:  if you shine a white
light through a blue glass, doesn't the light "turn" blue?  What am I
missing here?  I would expect the caustics here to be blue, right?  Thanks.

#declare M_Royal_Blue_Glass=material {
 texture {
  pigment {
   NewMidnightBlue*1.2 filter 0.75
  }
  finish {
   diffuse 0.8
   specular 1
   roughness 0.002
   reflection { 0.25 }
  }
 }
 interior {
  ior 1.5
  dispersion 1.1
  dispersion_samples 7
 }
}

light_source {
 <10, 75, -10>
 color <1, 1, 1>*1.05
 area_light
 x*8, y*4, 8, 4
 adaptive 1
 jitter
 circular
 orient
}
light_source {
 <10, 45, 10>
 color <1, 1, 1>*1.05/2
 area_light
 x*8, y*4, 8, 4
 adaptive 1
 jitter
 circular
 orient
}

object {
 center
 material { M_Royal_Blue_Glass }
 photons{
  target 0.5
  refraction on
  reflection on
  collect off
 }
}

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Attachments:
Download 'dc glass 2.jpg' (19 KB)

Preview of image 'dc glass 2.jpg'

cadman wrote:
>Two posts in a row!  Anyhow, forgive my ignorance:  if you shine a white
>light through a blue glass, doesn't the light "turn" blue?  What am I
>missing here?  I would expect the caustics here to be blue, right?  Thanks.
>

My guess is that the caustics you're seeing are a result of
reflection off the top surfaces of the glass object.  Have you
tried a render that looks underneath the glass?

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"cadman" <REM### [at] povraycouk> wrote in message
news:3dfb4cd0@news.povray.org...
> Two posts in a row!  Anyhow, forgive my ignorance:  if you shine a white
> light through a blue glass, doesn't the light "turn" blue?  What am I
> missing here?  I would expect the caustics here to be blue, right?  Thanks.
>
> #declare M_Royal_Blue_Glass=material {
>  texture {
>   pigment {
>    NewMidnightBlue*1.2 filter 0.75
>   }
>   finish {
>    diffuse 0.8
>    specular 1
>    roughness 0.002
>    reflection { 0.25 }
>   }
>  }
>  interior {
>   ior 1.5
>   dispersion 1.1
>   dispersion_samples 7
>  }
> }
>
> light_source {
>  <10, 75, -10>
>  color <1, 1, 1>*1.05
>  area_light
>  x*8, y*4, 8, 4
>  adaptive 1
>  jitter
>  circular
>  orient
> }
> light_source {
>  <10, 45, 10>
>  color <1, 1, 1>*1.05/2
>  area_light
>  x*8, y*4, 8, 4
>  adaptive 1
>  jitter
>  circular
>  orient
> }
>
> object {
>  center
>  material { M_Royal_Blue_Glass }
>  photons{
>   target 0.5
>   refraction on
>   reflection on
>   collect off
>  }
> }

I'm just guessing here, but I think it might relate to your dispersion samples not
being high
enough. If you turn off dispersion, do you get a blue tinted shadow?
Also, I always think that glass looks better using fresnel reflection.. you have a
constant
value of 0.25. I would try something like reflection (0.1,0.4 fresnel) (I'm sure these
values
are not technically correct.. I just made them up)

All the best,

Andy Cocker

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