POV-Ray : Newsgroups : povray.beta-test : A v3.8 / v4.0 divide by zero exposure AA sampling 3. Server Time
22 Jul 2024 10:57:03 EDT (-0400)
  A v3.8 / v4.0 divide by zero exposure AA sampling 3. (Message 1 to 1 of 1)  
From: William F Pokorny
Subject: A v3.8 / v4.0 divide by zero exposure AA sampling 3.
Date: 27 Mar 2024 08:42:18
Message: <6604142a$1@news.povray.org>
It happens when we end up with a single pixel within a within a thread 
rendering block; When neighborSamples in tracetask.cpp ends up as 1. My 
patch bumps that value to at least '2'. This makes the test to the 
threshold less forgiving, but at worst a few more samples are taken.

The single pixel in a render block isn't something which will happen 
often in practice(a).

As for what happens today on hitting this bug; It will depend on how 
your particular executable is compiled. If nothing else, it's
a component contributing to somewhat flaky render reporting. My fast 
compile ran without a squeak, but it also bailed too early on the AA for 
the single pixel.

Bill P.

(a) - The code involved here has some addition implications related to 
how many initial samples there are available in the block for a given 
pixel. The count changes downstream behavior. At the start of the 
sampling, I don't think it will matter much to the end result. This 
'concern' is mostly mitigated, if using yuqk's anti-aliasing min depth 
option with a depth >0.

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