Ok, I follow all of this but what happens why you are doing a lot of
differences which take up a majority of the image.

For example, I have something like this:

difference {
    box {
        <-10,0,-10>, <10,1,10>
        texture...
    }
    #while...lots of cylinders like this...
        cylinder {
            <xx, -0.1, zz>, <xx, 1.1, zz>, rr
        }
    #end
}

and my view of this scene basically is just this box thingy. Is there any
way to speed this up? If I bound the whole thing it doesn't help because
every ray hits it anyway. I can try to strategically bind the cylinders but
this doesn't seem to help much at all. The only way I can think of that
would help significanly is making a lot of small boxes with singly cylinder
differences and then putting all of them together to seem like a single
large box. For my real scene, however, this might be difficult. I'll look
into it.


--Rainer


----- Original Message -----
From: Ken <tyl### [at] pacbellnet>
>
>   The way the Pov calculates the intersection testing is related
> to it's use of internally generated bounding boxes. As you increase
> the number of objects in the difference operation the greater the
> number of intersecting surface tests the program is required to
> perform.
>   What I do do cut down on this intersection testing is to manually
> bound the difference operation. If you are differencing a 1 unit
> cube then add bounding with a 1.1 unit cube at the end of the
> difference operation. You should see a noticeable improvement.
>   You will also see where pov will issue a warning that you have
> unnecessarily used bounding. Ignore this message. It means nothing
> in this case. If you used bounding on a two object difference
> operation it would be true. Where you have multiple objects in the
> difference statement the warning message does not apply.
>
>
> --
> Ken Tyler
>
> mailto://tylereng@pacbell.net

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