[Rtk-users] rktforwardprojections: direction parameter

[Simon Rit]

Hi Joseph,
--direction sets the m_Direction member of the itk image class which
determinant must be one:
http://www.itk.org/Doxygen/html/classitk_1_1ImageBase.html#ad5441781a157615dfecc29d400743e02

In this case, you are actually setting the direction in the projection
stack. It is probably not going to work if you do more than simply
flipping x and y (--direction 0,1,0,1,0,0,0,0,1). I don't know what
you are trying to do but you should probably modify the geometry if
you want to rotate differently around your image, e.g.,
./rtksimulatedgeometry -o geometry.xml -n 100 -a 190 --sdd=1000
--sid=634 --out_angle 30.

You can read about the geometry here:
http://wiki.openrtk.org/index.php/Main_Page#Geometry

You can also tell us more on what you are trying to achieve if you
want us to help.
Simon

On Tue, Jun 25, 2013 at 1:11 PM, Görres, Joseph
<j.goerres at dkfz-heidelberg.de> wrote:
> Hi,
>
> we are new to RTK and would like to do a forward projection with cone-beam ct image data. We would like to use the rtkforwardprojections application, which works great with your example data. However, we have problems setting the direction differently.
>
> ./rtksimulatedgeometry -o geometry.xml -n 100 -a 190 --sdd=1000 --sid=634
>
> ./rtkforwardprojections -g geometry.xml -o projections.mha -i image.nrrd --spacing=1,1,33.3 --origin=-85.512,-61.8375,61.3525 --direction=0.0,0.0,1.0 --dimension 256
> terminate called after throwing an instance of 'itk::ExceptionObject'
>   what():  ~/ITK4/src/Modules/Core/Common/include/itkImageBase.hxx:196:
> itk::ERROR: Image(0x13b2880): Bad direction, determinant is 0. Direction is 0 0 1
> 1.63042e-322 4.24237e-315 0
> 0 1.63042e-322 1.01356e-316
>
> Aborted (core dumped)
>
> We compiled the newest RTK version with ITK 4.3.1.
>
> Thank you and best regards,
> Michael and Joseph
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