Hi guys

I am fairly new to PovRay and I have ran into some issues - wonder if you
can help?

1. What is a common trace time for complex images (lots of reflection /
refraction, many objects)

I realise this is subjective, but I have reasonably simple scenes (10 000
objects, and about 30 reflective/refractive objects, ten light sources)
that take literally weeks to render while various IRTC entries I have seen,
with scenes literally thousands of times more complex (as regards APPARENT
objects and reflections / refractions) done with PovRay, render in times of
2 or 4 hours. So IS two weeks tracetime (or even a month) for a 1152x864
image acceptable, or am I doing something exceedingly stupid? Or is this so
subjective its not worth an answer? I am referring to times on a
"standard"-ish system - P4 2.0 GHz with 512MB on Rh9 Linux, the raytrace
being the only user process running.

Is there anybody else out there with such long tracetimes? How did you
reduce them without losing scene quality?

2. How exactly to use adc_bailout?

To decrease render time in scenes with lots of reflections / refraction, it
seems to me that I should use larger adc_bailout values (0.05+ ?) and lower
max_trace_level values (5 or less?) The default values are taking simply
too long - and apparently there is no difference for me yet, as a test
scene is taking forty hours to get to a certain point, with or without
adc_bailout set to 0.05 and max_trace_level set to 5, while having the
reflective and refractive objects in that particular part of the image.

3. Aborting?

If I abort a trace in the middle of a horizontal line, do the pixels
calculated up to that point get saved to disk? I. e. if tracing one line of
1152 pixels takes two hours, and I abort an hour into the line, do I loose
all the pixels finished up to that point, or does PovRay resume from there?
Or does it start over a x=0 on that line? What if I force PovRay to exit
instead of CTRL-C (in Linux) and waiting for it to exit in its own time?
Can I force PovRay to write each, say, 25 pixels to disk? How does the
abort_count option influence this? Does it control how regularly pixels are
saved to file?

4. Pointers / hints?

Any URL's or info on PovRay optimisation? I have often looked for
optimisation guides for programming, but are there any for the PovRay scene
language?

5. Reasons for scanline renderers being faster - is scanline better?

I have seen images created with 3DStudio that would (I think) take YEARS to
render with PovRay. Which technique is better, i. e. which program is
better - a scanline renderer (what does that mean? What is the difference
between that and raytracing?) or a raytracer? I have heard about IPAS
modules for 3DStudio that do raytracing - so 3DS can do both? Why is
scanline so very much faster than raytracing, but looks just as good?

Anyway, thanks for your time!

Regards,

-- 
Stefan Viljoen
Software Support Technician
Polar Design Solutions

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