POV-Ray : Newsgroups : povray.binaries.images : Having a try at light distributions : Re: Having a try at light distributions Server Time: 20 Jun 2019 19:05:42 GMT
  Re: Having a try at light distributions  
From: Alain
Date: 15 May 2019 19:35:52
Le 19-05-15 à 10:11, William F Pokorny a écrit :
> On 5/13/19 1:56 PM, Norbert Kern wrote:
>> "Jasper" <nomail@nomail> wrote:
> ...
>>
>> OK, this doesn't have anything to do with radiosity - so I agree on 
>> floating
>> point precision issues as cause...
>>
>> Norbert
>>
> 
> Is this still true for you with recent v38 releases?
> 
> I'd captured the case(s) you posted a couple years back - my notes say 
> in 2016. I wasn't able to run what you posted directly on my little 
> machine, but a cut down scene was fixed when I tested a v3.71 branch 
> March 17, of 2017.
> 
> Bill P.

The version don't matter when you hit the FPU's limits.
Don't forget that in computing the illumination, there are a few 
squaring and square roots involved. This typically demand twice the 
number of bits of the input value if you want to avoid loss of precision.
When you square a 64 bits floating point value, you need 128 bits to 
accurately represent the result.


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