On 17 Sep 1999 03:13:21 -0400, Nieminen Juha wrote:
>  You can only be sure that an object is not affected by the clock value
>when it doesn't use any identifier which has been "touched" by 'clock'
>(or other identifiers which have been "touched", etc). The same thing for
>'clock_delta'.

clock_delta is a constant for a given animation sequence, isn't it?

>  This is not enought, though. An object may depend on the clock value even
>if it doesn't use any identifier. For example:
>  #if(clock<.5) sphere { 0,1 pigment { rgb 1 } } #end

This can still be detected, of course.  Anything that's inside an #if 
block or a #while block that is dependent on clock is automatically 
dependent on clock.

>  But even this is not enough. The object may depend on the contents of an
>external file (which is #read during parsing and which may change from
>frame to frame).

e.g. by using a preframe shellout, or by writing it during the parse of the
current frame.  And let's not forget #include files that are generated 
automatically by either of those methods.

Obviously such scenes couldn't be rendered with "smart reparsing."  It would 
have to be an option, and probably not a default option.  Alternatively, you
could have a way to explicitly mark objects as being fixed from frame to frame,
and anything that isn't so marked is automatically reparsed.  This wouldn't
even take too much change to the parser.

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