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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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tests/DiffractionGeometryTest.cpp
+25 -6
View File
@@ -117,13 +117,30 @@ TEST_CASE("DiffractionGeometry_SolidAngleCorrection","") {
x.BeamX_pxl(1000).BeamY_pxl(1000).DetectorDistance_mm(75);
DiffractionGeometry geom = x.GetDiffractionGeometry();
REQUIRE(geom.CalcAzIntSolidAngleCorr(0.0) == 1.0f);
REQUIRE(geom.CalcAzIntSolidAngleCorr(2 * M_PI) == Catch::Approx(0.5f * 0.5f * 0.5f));
// theta = 30 deg
// cos (2 * theta) = 1/2
// At the beam centre the correction is 1
REQUIRE(geom.CalcAzIntSolidAngleCorr(1000, 1000) == 1.0f);
// 2 * theta = 60 deg -> cos(2 * theta) = 1/2 -> correction = (1/2)^3
REQUIRE(geom.CalcAzIntSolidAngleCorr(1000 * (1.0 + sqrt(3)), 1000) == Catch::Approx(0.5f * 0.5f * 0.5f));
REQUIRE(geom.CalcAzIntSolidAngleCorr(1000, 1000 * (1.0 + sqrt(3))) == Catch::Approx(0.5f * 0.5f * 0.5f));
}
TEST_CASE("DiffractionGeometry_SolidAngleCorrection_TiltInvariant","") {
// The solid-angle correction depends on the incidence angle to the detector
// normal, so for a given pixel it must be invariant under a rigid detector tilt
// (rot1/rot2/rot3) -- the same behaviour as PyFAI solidAngleArray.
DiffractionExperiment x;
x.IncidentEnergy_keV(WVL_1A_IN_KEV);
x.BeamX_pxl(1000).BeamY_pxl(1000).DetectorDistance_mm(75);
DiffractionGeometry flat = x.GetDiffractionGeometry();
x.PoniRot1_rad(0.2).PoniRot2_rad(-0.1).PoniRot3_rad(0.5);
DiffractionGeometry tilted = x.GetDiffractionGeometry();
CHECK(tilted.CalcAzIntSolidAngleCorr(100, 100) == Catch::Approx(flat.CalcAzIntSolidAngleCorr(100, 100)));
CHECK(tilted.CalcAzIntSolidAngleCorr(1500, 400) == Catch::Approx(flat.CalcAzIntSolidAngleCorr(1500, 400)));
CHECK(tilted.CalcAzIntSolidAngleCorr(800, 1900) == Catch::Approx(flat.CalcAzIntSolidAngleCorr(800, 1900)));
CHECK(tilted.CalcAzIntSolidAngleCorr(1000, 1000) == Catch::Approx(flat.CalcAzIntSolidAngleCorr(1000, 1000)));
}
TEST_CASE("DiffractionGeometry_PolarizationCorrection","") {
@@ -424,7 +441,9 @@ Rot3: 0.0
Wavelength: 1e-10
*/
// Not sure why, but PyFAI solidAngleArray doesn't take into account poni rotation (???)
// PyFAI solidAngleArray is computed from the incidence angle to the detector normal,
// so it is independent of the poni rotation (tilt). CalcAzIntSolidAngleCorr matches this;
// the invariance is checked in DiffractionGeometry_SolidAngleCorrection_TiltInvariant.
DiffractionExperiment x(DetJF4M());
x.DetectorDistance_mm(200).BeamX_pxl(2000).BeamY_pxl(1000).IncidentEnergy_keV(WVL_1A_IN_KEV);
DiffractionGeometry geom = x.GetDiffractionGeometry();