POV-Ray : Newsgroups : povray.general : Media: rendering needs verry long for the last few percent : Re: Media: rendering needs verry long for the last few percent Server Time
20 Apr 2024 22:08:58 EDT (-0400)
  Re: Media: rendering needs verry long for the last few percent  
From: Alain Martel
Date: 4 May 2022 14:03:19
Message: <6272bfe7$1@news.povray.org>
Le 2022-05-03 à 18:12, Juergen a écrit :
> Hi,
> I've the following situation: a scene contains six objects with media (in the
> center of the image). They are small, approx 10% of the final image.
> When I render the scene (pov 3.7.0) the image is rendered to 97% in few minutes,
> but the last 3% needs more than one hour! This final time seems to depend on the
> amount of other objects in the scene, when I reduce them, the final part render
> faster (but reducing objects is not an option).
> What is povray doing at the end of the image?
> How can I speed this up ?
> Jürgen

It may be related to your media settings.
What is the sampling method ?
If using method 3, the default, did you increase the intervals value 
above 1 ? Using method 3, intervals MUST remain at 1. Increasing it 
greatly increase the rendering time for no effective improvement.
How many samples ? Try using less samples. Go as low as you can without 
degrading the quality of your render. A solid, uniform, media may need 
only 3 samples, while one using a busy pattern like granite or agate, or 
a highly turbulent one, could demand over 100.

Any overlapping media containers ? (having common volumes)
If your media containers overlap, it can cause some performance issues 
and cause artifacts. That's particularly true if one have a simple 
pattern demanding few samples and the other have a pattern demanding a 
high samples count.

Do those objects have an ior ?
A medium to high ior will cause total internal reflections.
Do you use dispersion ? Dispersion greatly increase the total number of 
rays needed.

Any reflective surfaces ?

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