"Jaap Frank" <jjf### [at] casemanl> wrote in message 
news:47d31681$1@news.povray.org...
> Hi,
>
> Recently I stumbled over a link to Chris Bartlett's StairCase macro
> and downloaded the files.
> The first example in StairCaseDoc.pov traced happily in about 7s
> with my AMD Athlon 64 3000+ on Windows XP Home SP2.
> Because all the examples trace as an animation, I started it with
> +kfi0 +kff50 in the command line box and went doing something
> else. After a while I checked the progress and noticed that the
> tracing was very slow compared to the single trace before.
> I quickly checked the messages for the first example and good only
> see a difference in the number of objects :
> Single trace: 176                Trace time: 7sec
> Animation:   168                Trace time: 68sec
> Weird, why is there a difference when everything in the file stays the
> same?

The 'StairCaseDoc.pov' file is designed to use the animation feature to 
regenerate all of the 50 different images in the documentation provided with 
the macros. When you use the animation feature with this file, the SDL uses 
the frame number to work out which image to generate, then sets the macro 
parameters for that image. Some of the images contain simple single flights 
of stairs with a small number of objects, others contain multiple flights of 
stairs with a very large number of objects. The render time therefore varies 
a lot from image to image/frame to frame.

> All my animation files are based on clock values and I never
> noticed any differences in trace time with a single trace or in
> an animation. However I never used the frame system of POV.
> In news.povray.org I can't find any reference to such a behaviour.

Even if you just use the clock and don't vary the contents of the scene 
between frames, the render times for different frames can still vary 
depending on the proximity to the camera of different objects. For example, 
a partially transparent or reflective sphere a long way from the camera has 
less impact on render times than if it's close to the camera and generates 
additional rays to trace.

Regards,
Chris B.

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