Chris Cason <del### [at] deletethistoopovrayorg> wrote:
> helge_h wrote:
> > Here is my file and output; the only difference between the two sessions is the
> > sphere radius - 1357 units makes finite objects that render fast, 1358 units
> > makes infinite objects that render much slower, and also where there are no
> > objects.
>
> ok, the code behind this is a test in the parser's post-processing that
> sets the infinite flag on any object whose volume exceeds a pre-defined
> value; in the case of 3.6 and 3.7 this value is 10,000,000,000 (10^10).
> the code itself was added in 1994.
>
> there might have been several reasons behind this; one would probably be
> related to bounding slab creation. there could be others (such as the
> render-time performance of slabs with objects of such large volume present).
>
> it's hard to say how much need there is for this today - if the reasoning
> was to reduce the memory use of bounding slabs, then it's probably less
> important than it used to be. if it was due to the efficiency of the
> bounding, then it's not so clear, as the operation of bounding slabs has
> not changed significantly.
>
> one thing that would be worth looking into is whether or not this is needed
> or desirable with +bm2 bounding. I suspect it is not.
>
> if you're willing to do an analysis on a large sample of scenes using a
> version of POV that allows this above-mentioned volume test to be disabled,
> and compare the results to the same scenes without it disabled, then I'll
> build a special EXE.
>
> -- Chris

Thanks a lot for your reply, nice to have an explanation, and good to know that
it will be considered in future versions of POV-Ray.

I'm sorry, I don't have the time to do any more on this.

It would be a good thing to make a note of it in the documentation, though,
since it has a significant effect on rendering times - 4 to 8 times as far as I
have seen.

H

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