"Kenneth" <kdw### [at] gmailcom> wrote:
>
> Long ago, I rendered a "Merry Christmas" image...
>
> The general idea is to have a very thin slice of translucent white (somewhat
> broken up) to appear inside the ice-- like a crack or fracture. Perhaps
> something similar might work for your crystal.

I found my original scene file from 2007(!), and re-rendered one of the ice
objects. I've attached the render as the code existed then. But looking at my
code, I see that I had used simple textures for the ice cracks, bubbles,
etc-- which are just surface attributes, not 'volumetric' inside the ice. At the
time, I didn't know how to do such interior tricks... which was frustrating.

BTW, this was my actual 'crack' pigment:
pigment{
      marble // marble or wrinkles
      color_map{
           [0.0 rgbt 1]
           [0.487 rgbt 1]
           [0.492 rgbt <1,1,1,.5>]
           [0.508 rgbt <1,1,1,.5>]
           [0.513 rgbt 1]
           [1.0 rgbt 1]
                }
           warp{turbulence 4 lambda .2}
           scale 40
           warp{turbulence .5 lambda .2}
        }

But my main ice material makes use of MEDIA (as does your crystal)-- so these
'surface' pigment patterns, being 3-D of course, could be made into functions
instead, then used as additional densities or density_map(s) for the media
itself... by way of 3 color functions there, like this simplified example...
    media{
    emission <1,0,0> // for the RED channel
    density{function{PIGMENT_FUNCTION(x,y,z).red}}
         }

This way, my cracks and bubbles will show up INSIDE the ice, as I had originally
wanted. And I think that this technique might work for your crystal too. (The
interior 'bubbles' or voids you mentioned could possibly be made with 'media
voids'-- e.g., areas in the pigment/function that have rgb <0,0,0>, which would
produce NO media density there, I think. Just a guess though.)

Without your crystal post here, I would not have thought of revisiting my ice
scene with these changes. Thanks! :-)

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