> What I ment was... if you render an image with AA=1/256 and then
> again with AA=1/512, you won't see a difference - unless you
> increase the bits/pixel setting.

Agreed.  Well aside from the fact that I didn't even know the
bits/pixel setting was adjustable.  I haven't had a need to play with
that yet.

> However, you're quite right - setting AA = EXACTLY ZERO will
> make a difference in the case of tiny objects (and other miniscule
> ray colour variations).

I thought I was right.  A thought hit me latter thought.  If you have a
flat backgroud the difference from pixel to pixel is also zero so you
have a is 0>0 situation.  Could this cause a floating point issue where
maybe the AA isn't done for every pixel?  Maybe the AA should be
set to -0.1?  Or maybe something like that is done internally when
the AA is set to 0.

> True - the intersection of *two* infinite planes would always be
> infinite. But the intersection of, say, 4 planes could be finite.
> (A pyrimid, for example!) Personally, a lot of my scenes involve
> generating irregular "facetted" shapes by intersecting a few
> hundred planes. Slows things down a touch if there's no manual
> bounding... (And then you have to figure out how to get it
> RIGHT! :-S)

Jellby's post cleared up the confusion this was causing me. See
my reply to his post.

> I don't know how your tank is constructed - if there are no
> infinite objects making it up, the automatic bounding *might*
> be ok...

Its a CSG of prisms, spheres, cones, tori, and boxes.  I think
that's all.  I defined all the cylinders as cones, as it was easier
for me to keep things strait in my head at the time.  That might
be costing me some rendering time too.  Do cylinders render
alot faster the cones?  I woudn't think it'd be that big of a
difference.  Oh I and do have one light source inside the
light cycle and two inside the tank so for the light to get out
all shapes are merged instead of being put together with
unions.  I'm sure that's costing me some too.  One odd
thing I have noticed is by putting a light souce inside the
objects I sometimes get a warning like "Patch objects not
allowed in intersections".  But it all works.

> (Question to anyone else reading this... What does POV-Ray
> do with the intersection of two large spheres which only slightly
> overlap?)

Good question... something I'll test with the Draw_Vistas
option you talk about below.  I'm thinking the bounding box
will be alot bigger then the small shape but I'm not sure.

I know when I was defining my models if I wanted a half
sphere I was throwing things together like this:

intersection {
  sphere {<0,0,0>, 20}
  box {<0,-1000,-1000>,<1000,1000,1000>}
}

just because I knew it would give me the shape I wanted.
Looking back at it now that MIGHT have been a very
big mistake.  Had I known planes behaved the way Jellby
pointed out I might have been using them.  It is in effect
what I'm doing above.

> Well, you never know. ;-)

I'll learn.  That's the important thing.

Thanks,
Carl

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