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azint: tilt-correct solid-angle correction; honour imported rot3 in refinement

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The azimuthal-integration solid-angle correction used cos^3(2*theta), where
2*theta is the true scattering angle (from LabCoord, including detector tilt).
The solid angle of a flat pixel actually depends on the incidence angle to the
detector normal, cos(alpha) = det_distance / |detector-frame position|, which is
invariant under detector tilt (rot1/rot2/rot3). Only for an untilted detector do
the two agree. Switch CalcAzIntSolidAngleCorr(x,y) to the tilt-invariant form,
matching PyFAI solidAngleArray and MAX IV azint. Drop the q-only overload (it can
only ever be the untilted approximation and was used only in tests) and move its
test onto the (x,y) form; add a tilt-invariance test.

XtalOptimizer's residual reconstructed each spot's lab position from rot1/rot2
only, hardcoding rot3 = 0, while the rest of the pipeline (and its own spot
selection) used the full PONI rotation. An imported non-zero rot3 was therefore
silently dropped during refinement. Bake rot3 into the residual as a fixed
Rz(-rot3) so refinement stays consistent (no-op when rot3 == 0).

Polarization and azimuthal binning already honoured rot3 via the full PONI
rotation (Phi_rad), validated against PyFAI chi() by the existing rot3 phi tests.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
This commit is contained in:
leonarski_f
2026-07-11 11:34:11 +02:00
co-authored by Claude Opus 4.8
parent e7fbeb527f
commit acd2025676
5 changed files with 55 additions and 24 deletions
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common/DiffractionGeometry.cpp
+9 -10
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@@ -87,17 +87,16 @@ float DiffractionGeometry::DistFromEwaldSphere(const Coord &recip) const {
return S.Length() - (1.0f/wavelength_A);
}
float DiffractionGeometry::CalcAzIntSolidAngleCorr(float q) const {
float sin_theta = q * wavelength_A / (4 * static_cast<float>(PI));
float cos_2theta = 1.0f - 2.0f * sin_theta * sin_theta; // cos(2*alpha) = 1 - 2 * sin(alpha)^2
float cos_2theta_3 = cos_2theta * cos_2theta * cos_2theta;
return cos_2theta_3;
}
float DiffractionGeometry::CalcAzIntSolidAngleCorr(float x, float y) const {
float cos_2theta = cosf(TwoTheta_rad(x, y));
float cos_2theta_3 = cos_2theta * cos_2theta * cos_2theta;
return cos_2theta_3;
// The solid angle of a flat pixel depends on the incidence angle to the detector
// normal, cos(alpha) = det_distance / |detector-frame position|. This is evaluated
// in the detector's own frame, so it is invariant under detector tilt (rot1/rot2/rot3),
// matching PyFAI solidAngleArray and MAX IV azint. It reduces to cos^3(2*theta) only
// for an untilted detector.
float u = (x - beam_x_pxl) * pixel_size_mm;
float v = (y - beam_y_pxl) * pixel_size_mm;
float cos_alpha = det_distance_mm / sqrtf(u * u + v * v + det_distance_mm * det_distance_mm);
return cos_alpha * cos_alpha * cos_alpha;
}
float DiffractionGeometry::CalcAzIntPolarizationCorr(float x, float y, float coeff) const {