Jim Charter <jrc### [at] msncom> wrote:
> How is it that case 1 gets a performance/memory gain and case 2 doesn't?

  When you create instances of a mesh, the mesh data is not copied. However,
when creating instances of a union, the contents are copied for each
instance.
  The reason is that transformations made to the instance may change the
contents of the union.
  In order to get the same advantage as with a mesh, all transformation
optimizations would need to be removed from all existing primitives.
This might have a negative impact on the rendering speed of some
scenes... (It's not an impossible idea, but it would be nice to know
how much it would impact in practice.)

-- 
plane{-x+y,-1pigment{bozo color_map{[0rgb x][1rgb x+y]}turbulence 1}}
sphere{0,2pigment{rgbt 1}interior{media{emission 1density{spherical
density_map{[0rgb 0][.5rgb<1,.5>][1rgb 1]}turbulence.9}}}scale
<1,1,3>hollow}text{ttf"timrom""Warp".1,0translate<-1,-.1,2>}//  - Warp -

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