In playing around with isosurfaces, I had included a
mostly-transparent box to help figure out where the edges of the
isosurface were. I just ran into a very odd situation where if that
box is there, my isosurface shows up, but as soon as I take it away,
the isosurface mostly disappears, leaving only the bottom fifth or so.


I tried, just to see if it would change anything, making the display
box completely clear (I thought maybe something strange was happening
with pigments) but that doesn't alter the results. Commenting out the
box removes the majority of the isosurface. Putting the box back in
brings it back. Isosurface by Acme.

Here's the (somewhat bizarre, too) code, using a freshly downloaded
MP0.7 for Windows. I used both versions of FStone, tried switching
sign, accuracy, method, and even the contained_by, and both included
and excluded the explicit F(x,y,z) parameters. I'm out of ideas.
Anyone? Anyone? [Something-D-O-O, Anyone?]


//#declare FStone=function { "Pillow" <1> } 
#declare FStone=function { (x^2-1) & (y^2-1) & (z^2-1) }

#declare FBozo=function {
  pigment {
    bozo
    color_map {
      [0.0 White*0.5]
     
      [1.0 Black]
      } // end cmap 
    scale .5
    }
  }

#declare ChippedGranite=function { noise3d(x*30, y*10, z*80)*0.7 } 

//box { -1.5, 1.5 pigment { Clear } }


isosurface {
  function { FStone(x,y,z)+0 - FBozo(x,y,z) + ChippedGranite(x,y,z) }
  sign 1
  accuracy 0.001
  method 2
  eval
  contained_by { box { -8, 8 } }
  pigment { rgb <.9, .9, 0> }
  finish { specular .6 roughness 1 brilliance .5 }
  }

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