[Rtk-users] Blurred piece-wise reconstruction

[Simon Rit]

Have you tried the combination of both? To be clear, --divisions acts on
the reconstructed volume so it should be ~7 Go with the "--divisions 4"
option (instead of 2000*2000*2000*4/1024/1024/1024=29.8 Go otherwise).
The --lowmem option acts on the projections and you have 250 Mo (instead of
2048*2048*1500*4/1024/1024/1024=23.4 Go otherwise).
The message "Failed to allocate memory for image" seems to be a CPU memory
issue. Are you sure you have about 10 Go available to run this
reconstruction?

On Tue, Feb 11, 2020 at 7:31 PM vincent <vl at xris.eu> wrote:

> Hi Simon,
>
> I am afraid I forgot to mention something in my last email.  I tried to
> use the lowmem option, as you suggested a while ago in the list for the
> same problem, but I am afraid I am still getting the same error.
>
> kind regards,
>
> Vincent
> On 11.02.20 17:36, Simon Rit wrote:
>
> Hi Vincent,
> There is a way to do such a thing in rtkfdk with the --divisions option,
> see code here
> <https://github.com/SimonRit/RTK/blob/master/applications/rtkfdk/rtkfdk.cxx#L190-L196>.
>
> I also don't really understand either what's going on in your bottom
> reconstruction, it seems to be a geometric problem. Have you checked an
> axial slice?
> Simon
>
> On Tue, Feb 11, 2020 at 4:21 PM vincent <vl at xris.eu> wrote:
>
>> Hello RTK community,
>>
>> I am afraid that my question might not be directly related to the
>> excellent implementation we are all using, but it might still be
>> interesting for some of you.
>>
>> I have a stack of 1500 projections of size 2048*2048.  I obviously can't
>> reconstruct the full resolution volume on my graphics card, as it is too
>> big.  So my solution was to split the sinogram into N parts, for which
>> each reconstructed volume would fit in my GPU memory and then reassemble
>> them.  I did a test with a 700*820*900 sinogram, that I cut in two parts
>> of 700*410(+a small overlap)*900.
>>
>> While the reconstruction of the whole volume was acceptable, I got a
>> weird issue with the split ones: the one corresponding to the top of the
>> image is also ok, but the bottom one is very blurry.  The three images
>> can be found at the following links:
>>
>> https://ibb.co/vLk9ZhQ
>> https://ibb.co/m4pm0LT
>> https://ibb.co/Jyf1yKM
>>
>> I used the same calibration parameters for the three reconstruction.  I
>> visually checked the split sinograms and they looked fine.
>>
>>
>> Any insight will be much appreciated !
>>
>>
>> Thanks in advance,
>>
>> kindest regards,
>>
>> Vincent
>>
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