POV-Ray : Newsgroups : povray.bugreports : Two BBox calculation bugs in CSG and Quadric? : Re: Two BBox calculation bugs in CSG and Quadric? Server Time
28 Sep 2021 19:01:15 EDT (-0400)
  Re: Two BBox calculation bugs in CSG and Quadric?  
From: William F Pokorny
Date: 26 Aug 2019 08:24:31
Message: <5d63cf7f$1@news.povray.org>
On 8/21/19 6:09 AM, William F Pokorny wrote:
> On 8/20/19 8:33 PM, Andreas Kaiser wrote:
...
>>
>> I don't remember anything in the code where it might help to set a big
>> but finite AABB to +/- infinity.
> 
> Yes, same here, but this looks to me to be the intent of that code.
> 
I've confirmed this is the behavior for the csg code with the test scene 
attached to the github issue.

>> Actually this turns off BBox testing for the corresponding object.
>>
> 
> I was thinking this too when I responded, but it's perhaps not entirely 
> true in 3.7 onward.
> 
> It's the case changes in 3.7/3.8 leave a last level bounding test around 
> the object even when bounding is off by -mb or +mb<count>. I have code 
> branch - now some years old - which re-enables the 3.6 and prior like 
> behavior of -mb. In other words, my branch really disables the inner 
> most bounding box test in a way similar to 3.6.
> 
> I'm wondering this morning whether that last level of bounding box test 
> is off for infinite objects? Though I have that patch, I just don't 
> remember the behavior of the code well enough to know without 
> investigation. If that inner most bounding test still gets done, it 
> might be this code hack is - in 3.7/3.8 - of no value in any case.
> 

In some quick tests it looks like when an object is infinite it's not 
tripping the bounding tests avoided by my patch branch. Given this at 
least sometimes true there is some potential for this code to be fixing 
or addressing some issue. In other words, see enough already to ignore 
the rambling above.

...
> 
> Lastly, I'd suggest we open up a github issue. Whether a bug or 
> intentional, seems to me the code related to CRITICAL_LENGTH should be 
> investigated.
> 

See: https://github.com/POV-Ray/povray/issues/379


Post a reply to this message

Copyright 2003-2021 Persistence of Vision Raytracer Pty. Ltd.