> Maybe it's worth first clearing up the term "evaluate".

Thanks for your detailed answer. I know it can't be easy to explain such an
'all-encompassing' question as mine-- particularly when I'm not being completely
clear with the proper terms to use (and I'm probably further confusing the issue
by discussing two different aspects of POV-ray as if they are one:
'instantiating' elements in a scene, and the operations performed during the
parse/render stages.) Honestly, I'm still 'groping my way through a fog' to
arrive at a proper set of intelligent questions ;-) And to fully understand some
of the details of your reply.

My use of the term 'evaluate' is probably a bit shabby and uninformed. What I
really mean is, 'where the hard time-consuming work is done.' For instance,
pre-#declaring an image_map for multiple use later: 'Evaluate' would mean,
'during the #declare step' (and the parse stage)... then it's simply
instantiated later, with no extra time-consuming work required during the parse
or render stages (a gross simplification of what really happens there.) In other
words, the greatest amount of time time is spent 'evaluating' that image_map
only once.

I obviously need a better phrase to describe that paradigm.

>
> Maybe what you mean is something I'd call "creating an instance" of, or
> just "instantiating", an object: Reserving a block of memory as required
> for a primitive of that particular type, and filling in the values
> required later during the render stage. This may include a few
> precomputed values, but for most primitives it is just the data
> specified in the SDL code.

Yes, that's basically it.

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