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Am 21.04.2015 um 23:29 schrieb Christian Baun:
> Le_Forgeron <jgr### [at] free fr> wrote:
>
>> The temporary buffer for 12800 x 9600 output is
>> sizeof(double)*5*dimensions (*) : that's 124F80000 bytes in hex, more
>> than can be represented on 32 bits.
>
> Hello,
>
> I have one more question.
> How can the value 5 in the formular be explained?
>
> 3 is quite easy to explain because of RGB. But why 5 ?
> Is it because of an alpha channel?
Theoretically, only 4 channels would be required (and if alpha output
isn't desired, 3 channels would actually do); however, all colour
storage inside POV-Ray has traditionally been using the "Red, Green,
Blue, Transmit, Filter" 5-channel colour model all throughout the
program, in each and every nook and cranny. Since the release of 3.7.0,
some effort has been made to clean up the internal colour handling to
only use a 3-channel RGB or 4-channel RGBA (or RGBT) colour model where
possible, but this process is still ongoing, and result image storage is
one area that hasn't been tackled yet.
I'm a bit puzzled though why a large image should result in problems, as
a mechanism has been in place for quite a while now to place large
output image buffers on hard disk rather than main memory, and this
mechanism is designed to cope with image sizes way beyond 4GB even on
32-bit systems. (Unless you happen to still use a Fat32 hard disk
partition, which indeed doesn't support files of 4GB size or more.)
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