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Add bindings to ASTRA cylindrical detector geometries #1634

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Add bindings to ASTRA cylindrical detector geometries #1634

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10e95bb
Convert cylindrical detector to astra vectors
wjp Apr 6, 2022
5fb20c1
Add FIXME note
wjp Feb 1, 2024
1f77075
Add det_curvature_radius property to ConeBeamGeometry.__repr__
wjp Apr 21, 2022
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Add FIXME note
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@wjp
wjp committed Feb 1, 2024
commit 5fb20c1b3cc2ef3ceb768becdf53a26ed3181fd6
3 changes: 3 additions & 0 deletions odl/tomo/backends/astra_setup.py
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Expand Up @@ -382,6 +382,9 @@ def astra_cyl_conebeam_3d_geom_to_vec(geometry):
vectors[:, 0:3] = geometry.src_position(angles)

# Center of detector in 3D space
# FIXME: This is not correct: det_point_position returns the zero-point of
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Actually, det_point_position return the center of the detector, so this is correct. The problem is with geometry.det_axes(angles), because axes are "attached" to the zero-point and not to the center as ASTRA assumes.

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@JevgenijaAksjonova JevgenijaAksjonova Feb 13, 2024 •
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I think the next few lines should look as follows:

    # Center of detector in 3D space
    mid_pt = geometry.det_params.mid_pt
    vectors[:, 3:6] = geometry.det_point_position(angles, mid_pt)
    # reverse the sign, since the partition angle in CylindricalDetector 
    # increases in the clockwise direction, by analogy to flat detectors
    det_shift_angle = -mid_pt[0]

    # `det_axes` gives shape (N, 2, 3), swap to get (2, N, 3)
    det_axes = np.moveaxis(geometry.det_axes(angles + det_shift_angle), -2, 0)

The detector partition along the first dimension is given in radians, so the distance from the mid_pt[0] to the 0 point is an angle. It is sufficient to add this angle to source angles to rotate the detector axes, however the sign should be reversed, because angles increase clockwise on the detector (to be consistent with the default setup for flat detector)

This solution does not affect the situation, when the detector is positioned symmetrically. So, one could still implement the detector shift by using detector_shift_func and rotating the axes.

# the detector, and not the center of the detector. For quarter-pixel-shifted
# detector these two do not coincide.
mid_pt = geometry.det_params.mid_pt
vectors[:, 3:6] = geometry.det_point_position(angles, mid_pt)

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