"sumdumguy" <nomail@nomail> wrote in message 
news:web.4927dbb3efcfba633b34ecfe0@news.povray.org...
> "Chris B" <nom### [at] nomailcom> wrote:
>> "sumdumguy" <nomail@nomail> wrote in message
>> news:web.4927c762fb7773f43b34ecfe0@news.povray.org...
>> >I have a scene where only a small part gets changed frame to frame so I
>> >want to
>> > render the first frame fully and then the following frames only for a
>> > selection
>> > of rows and columns, automatically keeping the rest of the pixel values
>> > unchanged from first frame. How do I do this?
>>
>> I don't think there's a straightforward way of doing this. If your desire 
>> to
>> do this is to save render time you may well find you expend more time
>> developing a technique to glue all the bits together than you save when
>> rendering.
>
> My goal is indeed to save time.
> Here is why +sc option is no good for me. If I use +sc options, the 
> resulting
> image will have the pixels I want and black pixels elsewhere. So far so 
> good.
> But the location of the "good" pixels within the total image will be 
> different
> from where they are in the first frame.
>
> Suppose I have a 1280x1024 image and I want to render row 2 through 5 and
> columns 2 through 5. Just a tiny patch. This will render fine and produce 
> a
> mostly black image whose size is 1280x1024. But the non-black patch will 
> not be
> between columns 2 and 5 and rows 2 and 5. It will be starting at row 1 and 
> it
> seems to be centered columnwise. So I cannot just use software to map 
> black
> pixels to 100% transparency and then paste the new image on top of frame 
> 1.
>
> The real problem is that for large images with tons of isosurfaces and
> anti-aliasing, the speed per frame is ~2 hours on my computer. If I can 
> animate
> 1/1000th of the image that changes, I can save days (actually weeks) of
> rendering.


Sounds like you're on 3.6, which indeed does what you describe.
I'm using 3.7 Beta 27 on Windows at the moment and that seems to place the 
pixels in the right place within the generated bmp image. It may be best and 
quickest to try the 3.7 Beta for this (You can still keep a copy of 3.6 
installed alongside it).

Regards,
Chris B.

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