I started to read this tutorial and found the first error in less than
one minute... :)
  I quote:

> bounded_by - This gives the isosurface a limit. For instance, if you make an
> isosurface sphere that is larger than 1 at its radius, and you put 

> bounded_by{ box{ <-1,-1,-1>,<1,1,1> } } 

> in the isosurface statement, what do you think will happen? The box will
> cut into the sphere, giving you an intersected box and sphere, the sphere
> having 6 flat sides. 

  I don't know if this works differently with isosurfaces since I have never
used the superpatch, but if bounded_by works as usual, that's not true.
  I think that you are confusing bounded_by and clipped_by together.
clipped_by cuts the object like an intersection does (except that it doesn't
add a new surface to the cut part). bounded_by just bounds the object. The
result is that the object becomes clipped by the projection of the bounding
object on screen. This is completely different from being clipped in
3D-space.
  If you want your bounding object to also clip the object, you have to do:

clipped_by { box { -1,1 } }
bounded_by { clipped_by }

-- 
main(i,_){for(_?--i,main(i+2,"FhhQHFIJD|FQTITFN]zRFHhhTBFHhhTBFysdB"[i]
):5;i&&_>1;printf("%s",_-70?_&1?"[]":" ":(_=0,"\n")),_/=2);} /*- Warp -*/

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