> >
> > I'd like to discover a cheap and realistic way to add internal fractures to
> > mineral renders. Apophyllite is one of those minerals prone to being
> > found in a fractured state. I have two ideas in mind, but both are
> > rather expensive:
> > 1) height fields intersecting not only each other, but also the crystal
> > shape (which is itself an intersection); or 2) isosurfaces. Both can be
> > very, very slow. Sometimes I wish media had an ior block.
> >
> Ah... yes indeed. I have not considered your first method, but
> considered the isosurface one. However, I also cringe at the implied
> render time.
>

A beautiful crystal, Thomas-- and with those VERY nice caustics.

Long ago, I rendered a "Merry Christmas" image (which I can't find,
unfortunately), that had some objects made of translucent ice, with an ior. I
wanted internal 'cracks' to show up inside the ice-- so IIRC I accomplished that
as part of its 3-D texture, not as actual geometry. It looked decent enough to
fool the eye. Something *kind of* like this pseudo-code example:

pigment{
   gradient x
   pigment_map{
            [0.49 --ice color --]
            [0.49 bumps (?)
                 -- some scale ---
                  pigment_map{
                      [0.3 -- ice color --]
                      [0.3 rgbt <1,1,1,.7] // translucent white
                             }
                  scale 50 // to scale down the size of the warp effect
                  warp {turbulence .2}
                  scale 1/50
            ]
            [0.51 same as 0.49]
            [0.51 -- ice color --]
                 }
         }

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.

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