POV-Ray : Newsgroups : povray.windows : Strange delay for larger sized renders : Re: Strange delay for larger sized renders Server Time
19 Jun 2021 06:26:07 EDT (-0400)
  Re: Strange delay for larger sized renders  
From: Le Forgeron
Date: 5 Dec 2016 16:07:15
Message: <5845d703$1@news.povray.org>
Le 05/12/2016 à 19:15, William F Pokorny a écrit :
> On 12/05/2016 12:23 PM, Bald Eagle wrote:
>> Probably somewhat related to:
>>
http://news.povray.org/povray.windows/thread/%3Cweb.56edd77df9a19c455e7df57c0%40news.povray.org%3E/
>>
>>
>> When I begin a render on a large size resolution image (10240 x 7680),
>> PPOV-Ray
>> seems to "hiccup" - it pauses, I get the spinny torus thing, the title
>> bar says
>> "[unresponsive]" and then it kicks in, I get the usual messages, and
>> the parsing
>> continues as usual.  This seems odd to me and less related the delayed
>> stopping,
>> because the rendering hasn't started yet - because the parsing hasn't
>> even begun
>> yet.
>>
>> Has anyone else experienced this behaviour?
>>
>>
> 
> Are you setting the max image buffer memory to something larger than the
> default of 128MB? I'm not sure of the exact memory footprint, but
> suppose you'd need at least than 10240x7680x4x4 ~= 1260MB to keep the
> image in memory.
> 
> Ref:
> http://wiki.povray.org/content/Reference:General_Output_Options
> 
> I admit to not having played with this option myself...
> 
> Bill P.

You probably have a point. From my memory, Windows won't make a sparse
file for the image buffer, but allocate every sectors of it when povray
write the first bytes in it (at the very end of the file, there is a few
data that are written for later recovery).

So it needs to write about 10240 x 7680 x 5 x 4 bytes (+ a few extras),
about 1.573 GB.
At average 50 MB per second (traditional speed of write on HDD), it
would take at least 30 seconds. But things can be worst.

4 bytes: for size of float
5 for the channels of the render (RGBFT)
the other numbers, you know where they come from.


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