In article <39ad151a@news.povray.org> , Geoff Wedig 
<wed### [at] darwinepbicwruedu>  wrote:

> I've kind of wondered about that.  I have a scene that parses in 15 minutes,
> or rather, all the *code* is read in in 15 minutes.  All the #render lines
> are printed, but it's another 2.5 hours before it gets around to setting up
> the scene.  Why is this?  Does it do a preparse, where it checks the code,
> then allocates memory?  The scene is memory intensive, so that would make
> sense.
>
> However, it's really annoying.  I use the #render messages to know how far
> it's gotten in the parse, but it's useless if it only tells how far it is in
> the parse and not how far along it is towards actually starting on the
> scene.

Once parsing is done, POV-Ray generates bounding boxes.  This will take
additional memory, and if at this time your system runs out of physical
memory, it will cause a significant slowdown due to swapping.

You can turn off building of bounding boxes which will make this stage
faster at the expense of rendering speed.  As building the bounding boxes in
an internal process that happens after parsing, you can't see anything.

> The other question I have is, why does memory allocation take so long
> compared to the inital parse?

Memory is managed by the operating system and in general requires more or
less advanced algorithms (depending on whether you expect lots of small or a
few big blocks, average number expected per application, and millions of
other small issues).


     Thorsten


____________________________________________________
Thorsten Froehlich, Duisburg, Germany
e-mail: tho### [at] trfde

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