Alain <aze### [at] qwertygov> wrote:
> Off field objects don't take time during render time unless they are 
> made visible by a reflection or refraction

  Actually that might not be completely true.
  For each ray sent from the camera POV-Ray has to test if it hits the
off-screen object. This is usually done by testing the ray against the
bounding box of the object which is often faster, but still takes its
little amount of time (which is more than would be if there was no
object at all).
  The bounding box of the off-screen object may even be partially inside
the view (even though the object itself isn't) and thus POV-Ray will make
a full ray intersection test against that object.

  Btw, the vista buffer technique probably alleviates a lot the problem
of off-screen object testing (if the object is not in the vista buffer
it can be skipped completely for rays sent from the camera). However,
vista buffer doesn't work eg. on infinite objects (eg. planes) and it
doesn't help if the bounding box of the object is partially on screen.

  But all in all, removing off-screen objects should not usually have
any big impact on rendering times (excluding some pathological cases).

-- 
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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