Op 31/10/2021 om 17:17 schreef Kenneth:
> "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! :-)
> 

Thanks for this Kenneth! At first glance, even these 'surface' patterns 
look great. I guess that your 'media' variant will work; I shall turn to 
that soon, as I have currently a render with 'real' bubbles (spheres, 
15000 of them) rendering. It looks good at first glance but the render 
time has dropped severely, although not dramatically. I am not yet sure 
about those 'media voids'... I shall have to think about that.

I shall make asap a scene file available and post it here. At this 
moment, it is in a terrible flux state and hardly readable, even for me. ;-)

-- 
Thomas

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