POV-Ray : Newsgroups : povray.general : Tracking down slow renders : Tracking down slow renders Server Time
10 Dec 2023 12:21:07 EST (-0500)
  Tracking down slow renders  
From: Chris R
Date: 5 May 2023 12:00:00
Message: <web.64552710e0749914159bf83b5cc1b6e@news.povray.org>
I have found in a few of my last projects that while doing a high-quality
render, (0 threshold anti-aliasing, hefty radiosity settings, etc.), that about
98-99% of the scene is rendered in a reasonable amount of time, and then it
seems as if no progress is ever made again.  The one I am rendering now
completed 98% in about 4 hours, but in the past 15 hours, with 10 patches
remaining to render, it has made no progress whatsoever.

This particular scene only has 2 light sources, a sunlight source as a 3x3 area
light, and one other light source also 3x3.  Most of the scene consists of
isosurfaces, usually some sort of block whose edges and faces have been
perturbed to give them texture.  The finishes are all fresnel, and there is a
tiny bit of reflection added in.  (A previous scene with this problem completed
98% in less than a day, and then made no progress for another week before I gave

Lowering the radiosity settings or the anti-aliasing settings allows the
rendering to finish, but at reduced quality.

Is there any way to turn additional debugging output to see where the render
engine is spending its time?  What I'm afraid of is that some interaction
between anti-aliasing, radiosity, and reflection is causing an infinite loop
measuring against thresholds.

Also, can someone verify that the rendering rate in the status bar (for Windows
at least), is just total pixels rendered/total time?  Is there any way to get a
rendering rate over the past N minutes instead?  For most scenes, once the
render settles down, the rate gives me a good estimate of the time to complete,
but in these long renders its not even close.

-- Chris R.

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