NXmx says how the stored image sits in the detector plane, in the NXdetector_module
fast_pixel_direction and slow_pixel_direction vectors. rugnux read neither, and
assumed every detector was mounted the way this system mounts its own. A facility
that bolts its detector a quarter turn round therefore produced a geometry that
was wrong by 90 degrees, which no amount of refinement recovers: the run indexed
nothing and reported that it could find no lattice.
The two vectors are read, taken from McStas into the internal frame, and matched
against the eight discrete image orientations. An exact match is adopted; anything
else is left alone, because an orientation that is not discrete is a continuous
rotation of the detector in its own plane and cannot be told apart from the tilt by
looking at the module. Every file examined here is exactly discrete.
Measured over the 94-dataset battery: 78 masters state no module vectors at all and
12 state the standard ones, so the change can reach exactly 4. Three of those go
from "Nothing was integrated" to a complete merged result with no flags -
43/93/92% indexed, CC(1/2) 0.957/0.984/0.998 - and are the sets that until now
needed a hand-passed --rot3 pi/2. The fourth states a half turn, which the existing
rotation-axis sign rescue already absorbed, and is unchanged to every digit.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Lc5JG6kJqZoCWaoZ43JGTW
leonarski_fandClaude Opus 5
08f57235d6