"Alain" <aze### [at] qwertygov> wrote in message
news:40cecb48$1@news.povray.org...
> Hughes, B. nous apporta ses lumieres ainsi en ce 14/06/2004 21:20... :
> >
> >#declare Hemisphere=
> >intersection {
> >  plane {-y,0} // could use x, instead of y, for East/West
> > // negative y for northern hemisphere, positive for southern
> >  sphere {0,1}
> >  pigment {color rgb <1,1,1>}
> >}
> >
> I prefer to use a box instead of a plane like:
> intersection{
>     sphere{0,1}
>     box{<0,1.1,1.1>,-1.1}
>     pigment{MyPigment}
>     scale MyScale
>     }
>
> That way, the bounding is more efficient (tighter)

I was going to concede about this until I decided to try a test of the two
ways.

Yours parsed and rendered slower, than mine, (in version 3.6) over several
runs, rather consistently too. I put them into a while loop, making a
150X150 grid facing the camera. Output image resolution was 1280X1024 and
default AA used. I kept the number of objects down to prevent going to XP's
Page File, so it wouldn't interfere.

plane = Parse: 1 to 2 seconds Render: 19 to 20 seconds, or averaging 21
seconds total.

box = Parse: 2 to 4 seconds Render: 23 to 24 seconds, or averaging 27
seconds total.

Perhaps imprecise, being so short-lived, but I believe it is showing the
introduction of the box is actually causing a loss of optimization or
something. I don't know the truth behind the numbers; it just looks like the
plane has an advantage, at least in this case.

Bob H.

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