Hi,

here I am sitting since almost SIX DAYS rendering with POV-Ray an
8000x45000pixel version of my spaceship, and just when it reached 98%, a
faultily attached USB device caused a restart of my computer.

I wanted to continue the rendering of that image, but I cannot find the
partially rendered image in its folder.

I used RECUVA and tried to find the SIX-DAY-Rendering image among the
deleted files, no success. it has disappeared.

1. Any idea where I can find this image and/or how to restore it?
2. Wouldn't it be a very, very wise solution to have POV-Ray creating
first a temporary image and just on completion writing the original
image (preventing image loss in cases like this)?

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Am 06.01.2016 um 18:18 schrieb Sven Littkowski:
> Hi,
> 
> here I am sitting since almost SIX DAYS rendering with POV-Ray an
> 8000x45000pixel version of my spaceship, and just when it reached 98%, a
> faultily attached USB device caused a restart of my computer.
> 
> I wanted to continue the rendering of that image, but I cannot find the
> partially rendered image in its folder.
> 
> I used RECUVA and tried to find the SIX-DAY-Rendering image among the
> deleted files, no success. it has disappeared.
> 
> 1. Any idea where I can find this image and/or how to restore it?
> 2. Wouldn't it be a very, very wise solution to have POV-Ray creating
> first a temporary image and just on completion writing the original
> image (preventing image loss in cases like this)?

The "+C" command line option is your friend in such cases. It lets
POV-Ray pick up an aborted render.

The reason you're not seeing any temporary image data is that as of 3.7,
POV-Ray uses a proprietary format for that purpose.

There also exists a documentation of that format... somewhere.

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Hi, and thanks. Yes, I know about the "+c" parameter. But usually, I see
an unfinished image in that folder. Okay, will try to continue and hope,
you're right. Don't want the continued render to replace anything if
there was any error before due to the crash and restart... :-)

Update will come.

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Am 06.01.2016 um 19:36 schrieb Sven Littkowski:
> Hi, and thanks. Yes, I know about the "+c" parameter. But usually, I see
> an unfinished image in that folder.

No you don't. Not with 3.7.

You used to see that with 3.6, because it supported progressive file
output: It simply created the output file when it started the render,
wrote the header, added data as the render progressed pixel line by
pixel line, and finally added the finishing touches to the file after
the render finished. (It should be noted that if the render aborted,
technically the output image was usually broken; it just so happens that
most image file formats are quite robust to this type of damage, and
allow the written portions of the file to be salvaged.)

In 3.7, progressive file output is no longer that easy to implement,
because render results no longer come in sequentially line by line, but
rather block by block in a somewhat random fashion. To maintain a
partially finished output image and keep it up-to-date with every
finished block, you'd have to roll back portions of the written image,
and re-write them (a feat that isn't supported by most image output
libraries), or discard the image and rewrite it from scratch (which also
has various drawbacks).

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This is (as usual) a good explanation of the POV-Ray features and inner
functioning. Thanks. And yes, the render continued without problems. :-)

This topic can be considered as closed.

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