About which axis does the source rotate?

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Hi,

I just want to confirm that the source always rotates around the axis x=0, y=0 
(i.e. z-axis)?  And due to the way the program is setup, this z-axis is always 
at the edge of the voxel volume?

This seems to cause trouble if one wants to produce CT datasets.  In the ".in" 
file, to get the voxel volume to project to the center of the detector on the 
first projection one must offset the source's coordinates in the ".in" file to 
be half of the voxel volume size in each dimension.  However, since the source 
continues to rotate around the z-axis and not the axis parallel to the z-axis 
that runs through the center of the volume.  Thus, the object rotates 
eccentrically relative to the detector and tends to "fall off" the detector at 
most angles when the field of view is small.

Is this the case, or do I understand the ".in" file incorrectly?  Is one 
supposed to fix this problem by changing the source cosines?  Or should I edit 
the source trajectory function (void set_CT_trajectory(...)) to try to make it 
so the voxel volume is centered in the field of view throughout a CT 
acquisition.

Thanks!

Jared

Original issue reported on code.google.com by jaredwmo...@gmail.com on 4 Feb 2013 at 7:12