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[Imgcif-l] Goniometer axis question

Dear All,

In an effort to understand how multiple axes are handled in CBFlib I "faked up" a toy goniometer which I chose to call FRED, which has a lot in common with a 50 degree kappa axis:

loop_
_axis.id
_axis.type
_axis.equipment
_axis.depends_on
_axis.vector[1] _axis.vector[2] _axis.vector[3]
_axis.offset[1] _axis.offset[2] _axis.offset[3]
GONIOMETER_FRED  rotation goniometer . 0.643 -0.766 0 . . .
GONIOMETER_OMEGA rotation goniometer GONIOMETER_FRED 1 0 0 . . .
SOURCE           general source . 0 0 1 . . .
GRAVITY          general gravity . 0 -1 0 . . .
DETECTOR_Z       translation detector . 0 0 -1 0 0 0
DETECTOR_Y       translation detector DETECTOR_Z 0 1 0 0 0 0
DETECTOR_X       translation detector DETECTOR_Y 1 0 0 0 0 0
ELEMENT_X        translation detector DETECTOR_X 1 0 0 -126.30 144.39 0
ELEMENT_Y        translation detector ELEMENT_X 0 1 0 0 0 0

loop_
_diffrn_scan_frame_axis.frame_id
_diffrn_scan_frame_axis.axis_id
_diffrn_scan_frame_axis.angle
_diffrn_scan_frame_axis.displacement
FRAME1 GONIOMETER_FRED  30.0 0.0
FRAME1 GONIOMETER_OMEGA 24.4499 0.0
FRAME1 DETECTOR_Z 0.0 800.02
FRAME1 DETECTOR_Y 0.0 0.0
FRAME1 DETECTOR_X 0.0 0.0

loop_
_diffrn_scan_axis.scan_id
_diffrn_scan_axis.axis_id
_diffrn_scan_axis.angle_start
_diffrn_scan_axis.angle_range
_diffrn_scan_axis.angle_increment
_diffrn_scan_axis.displacement_start
_diffrn_scan_axis.displacement_range
_diffrn_scan_axis.displacement_increment
SCAN1 GONIOMETER_FRED  30.0000 0.0 0.0 0.0 0.0 0.0
SCAN1 GONIOMETER_OMEGA 24.4499 0.0500 0.0500 0.0 0.0 0.0
SCAN1 DETECTOR_Z 0.0 0.0 0.0 800.02 0.0 0.0
SCAN1 DETECTOR_Y 0.0 0.0 0.0 0.0 0.0 0.0
SCAN1 DETECTOR_X 0.0 0.0 0.0 0.0 0.0 0.0

(I presume that cbflib is not upset by silly goniometer names, I got no errors). Anyway offsetting this axis by 30 degrees then asking for the rotation axis I got (1, 0, 0) not the offset axis I was expecting. Checking through the documentation in Tables G it seems that the cbf_get_rotation_axis which is used in pycbf *should* do this.

Looking at the actual code in cbf_simple I do however see:

    /* Currently just return the first rotation axis */

Would I be right in thinking that this is an aspirational method which still needs implementing, or am I perhaps looking in the wrong place? It would be consistent with my observations.

I checked it out from the code mentioned in Herbert's most recent email...

Thanks in advance & best wishes,

Graeme

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