Yes, the origin is the center of the first pixel in ITK see e.g. figure 4.1 of ITK's software guide <https://itk.org/ITKSoftwareGuide/html/Book1/ITKSoftwareGuide-Book1ch4.html#x45-54001r1> . Simon
On Mon, Jun 26, 2023 at 11:03 AM Albert MURIENNE <albert.murie...@b-com.com> wrote: > Hello Simon, > > > > Glad to hear you’re still actively maintaining RTK J > > I made some tests following your advices, and everything is now working > fine! > > I had already started playing with the projections origin, but I was > missing the point about the rotation convention. > > I guess the xxx.75 origin coordinates are related to the origin being at > the “center” of the pixel? > > > > Regards, > > > > Albert > > > > *De :* Simon Rit [mailto:simon....@creatis.insa-lyon.fr] > *Envoyé :* jeudi 22 juin 2023 11:47 > *À :* Albert MURIENNE <albert.murie...@b-com.com> > *Cc :* rtk-us...@openrtk.org > *Objet :* Re: [Rtk-users] Problem reconstructing from synthetic data > > > > Hi Albert, > > Nice to hear that you are still working on CT. There are two things that > must be accounted for > > - there is a difference in convention for the rotation angle between > gVirtualXRay and RTK, > > - the projections are not centered if the origin is 0. > > The following command lines work for me: > > rtksimulatedgeometry -n 360 -a -360 -o g --sdd 1000 --sid 500 > rtkfdk -p . -r 'projection([0-9]*).tif' -o fdk.mha --neworigin > -159.75,-119.75,0 --newspacing 0.5 --nsort --submatch 1 --hardware cuda -g g > > Let me know if something is unclear, > > Simon > > > > On Wed, Jun 21, 2023 at 10:04 AM Albert MURIENNE < > albert.murie...@b-com.com> wrote: > > Hello, > > I'm struggling to reconstruct properly a synthetic projection images > sequence using RTK. > The sequence was generated using gVirtualXRay ( > https://gvirtualxray.fpvidal.net/) and a dragon 3D model, and represents > a full 360 degrees CBCT tomographic sequence, with a 500mm SID and 1000mm > SDD, 0.5mm pixel size with a 640x480 image resolution, and without any > offsets (perfect circular geometry). I tried reconstructions with the > simplest FDK and SART implementations, inspired by RTK provided code > examples, using rtk::ProjectionsReader to read the images and > rtk::ThreeDCircularProjectionGeometry to read the geometry, but the results > are not good, and I don't really know if the problem comes from the data or > from my reconstruction implementation. > > The images data, as well as the xml geometry I generated, are available > for download at this link: > > > https://filesender.renater.fr/?s=download&token=bc8f87b4-989c-46d7-8c4b-dac39a4df0e1 > > Could you help me pinpoint the origin of my problem? Does it come from the > data itself? > > Thanks, > > Albert > Murienne > > _______________________________________________ > Rtk-users mailing list > rtk-us...@openrtk.org > https://www.creatis.insa-lyon.fr/mailman/listinfo/rtk-users > >
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