I'm rendering a sequence of frames in which certain objects in the scene
rotate, but most of the scene stays the same from frame to frame.

I just happened to be looking at the Messages window during the rendering,
and noticed that each frame seems to take longer than the last to render.
E.g. the first frame took 15 minutes, the next took 17, and so on until
8 or 9 frames later it was taking 28 minutes.

This would be understandable to me if the scene were changing in complexity
from one frame to the next, but as far as I can tell it is equally complex
in each frame.

Has anyone noticed this phenomenon before?  I saw there was a thread earlier
this month asking about increasing amounts of RAM being used in each frame;
it's possible the two issues are related (I haven't been watching the RAM
usage).  However, I'm using v3.6, not v3.5.

[Warning: slight digression follows]  It reminds me of the time I did an
"animation" to test the various radiosity presets.  I set up a fixed scene
(i.e. didn't use clock anywhere) and set the Radiosity_Settings value to
frame_number.  Then I started up a 10-frame "animation" and left the
computer for a few hours while it cranked through them.  Except I didn't
want it to do the REALLY slow settings such as Final or OutdoorHQ, so I
put in a little if/then that set the Radiosity_Settings to 0 (i.e. Default)
for both of those.  Much to my surprise, the first time it ran with Default
it took four hours to render, but later when it ran with Default again it
took less than 1/2 an hour.  Same scene, same radiosity preset, 8x diff
in rendering time.  Never did figure that one out!

But anyway, back to my question:  Does anyone know of anything that POV-Ray
does while rendering an animation sequence that would explain why very
similar frames would take successively longer to render?

Thanks,
wr.

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