Re: Deep data API: another batch of questions.

Thanks for your answer. I didn't thought I could pass an "illegal" pointer
to the function, i'll try this method instead.


2014-04-21 0:19 GMT+02:00 Peter Hillman <[email protected]>:

>  You will need to call setFrameBuffer before every call to writePixels, as
> you need to update the frame pointers.
> The pointer you pass to Slice/DeepSlice is the memory location of pixel
> (0,0) in the image. This point will move in memory as you update your
> memory block with different scanlines.
>
> Your first call is probably doing the right thing. For each subsequent
> call you need to set up a new FrameBuffer with yStride*currentScanLine()
> subtracted from the base pointer, where currentScanLine() is the y offset
> of the first scanline you are writing.
>
> The library will only access the memory locations it needs to for
> writePixels() - there's no problem in passing an "illegal address" as a
> base pointer to setFrameBuffer, as long as (base+yStride*currentScanLine()
> + dataWindow.min.x*xStride) is always a valid location when writePixels()
> is called.
>
> The above is true for xSampling=1 and ySampling=1 - you may need to adjust
> the logic accordingly otherwise.
>
>
>
> On 19/04/14 21:18, Lerenard Michel wrote:
>
>      Hi,
>
>  still trying to write deep data image, i'm struggling a bit with
> FrameBuffers.
>  As I need to write subsampled deep images, I cannot use Tiled images. I
> went for the scanline approach. My idea was to write batches of n
> scanlines, in increasing Y order.
>
>  This way I was thinking I would be able to limit the memory footprint:
>  OpenEXR would not need to cache data, and I would be able to reuse the
> same buffers for every batch of lines: one buffer for Z and one for each
> visible channel.
>
>  So I created a bunch of buffers, whose size was my image width * 32.
> (arbitrary value). I planned to feed these buffers to the DeepSlices I
> added to the FrameBuffer.
> Thing is, it appears the FrameBuffer/Slices cannot work that way: they
> need to have memory allocated for the whole image. I couldn't find any
> function limiting / defining the region I want to work on.
>
>  Here are my questions:
>  - Is the statement above correct ?
>  - Should I work differently ? I doesn't look like using several
> framebuffers would help, I out of ideas at the moment.
>
>  I can explain in more details my process if it can help.
>
>
>  Thanks
>
> Michel
>
>
> _______________________________________________
> Openexr-devel mailing [email protected]://lists.nongnu.org/mailman/listinfo/openexr-devel
>
>
>

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