Jungfraujoch/tests/DiffractionGeometryTest.cpp

// SPDX-FileCopyrightText: 2024 Filip Leonarski, Paul Scherrer Institute <filip.leonarski@psi.ch>
// SPDX-License-Identifier: GPL-3.0-only

#include <catch2/catch_all.hpp>

#include <iostream>
#include "../common/DiffractionGeometry.h"
#include "../common/DiffractionExperiment.h"
#include "../common/JFJochMath.h"

TEST_CASE("RecipToDetector_1", "[LinearAlgebra][Coord]") {
    DiffractionExperiment x(DetJF(8, 2));
    x.BeamX_pxl(1024).BeamY_pxl(1024).DetectorDistance_mm(120);
    DiffractionGeometry geom = x.GetDiffractionGeometry();

    float pos_x = 512, pos_y = 512;

    auto recip = geom.DetectorToRecip(pos_x, pos_y);
    auto [proj_x, proj_y] = geom.RecipToDetector(recip);
    REQUIRE(proj_x == Catch::Approx(pos_x));
    REQUIRE(proj_y == Catch::Approx(pos_y));
    REQUIRE((recip - geom.DetectorToRecip(proj_x, proj_y)).Length() < 0.00000001f);
    REQUIRE(std::fabs(geom.DistFromEwaldSphere(recip)) < 4e-4);
}

TEST_CASE("RecipToDetector_2", "[LinearAlgebra][Coord]") {
    DiffractionExperiment x(DetJF(8, 2));
    x.BeamX_pxl(1024).BeamY_pxl(1024).DetectorDistance_mm(120);
    float pos_x = 1023, pos_y = 1023;
    DiffractionGeometry geom = x.GetDiffractionGeometry();

    auto recip = geom.DetectorToRecip(pos_x, pos_y);
    auto [proj_x, proj_y] = geom.RecipToDetector(recip);
    REQUIRE(proj_x == Catch::Approx(pos_x));
    REQUIRE(proj_y == Catch::Approx(pos_y));
    REQUIRE((recip - geom.DetectorToRecip(proj_x, proj_y)).Length() < 0.00000001f);
    REQUIRE(std::fabs(geom.DistFromEwaldSphere(recip)) < 4e-4);
}

TEST_CASE("RecipToDetector_3", "[LinearAlgebra][Coord]") {
    DiffractionExperiment x(DetJF(8, 2));
    x.BeamX_pxl(1024).BeamY_pxl(1024).DetectorDistance_mm(120);
    float pos_x = 30, pos_y = 30;
    DiffractionGeometry geom = x.GetDiffractionGeometry();

    auto recip = geom.DetectorToRecip(pos_x, pos_y);
    auto [proj_x, proj_y] = geom.RecipToDetector(recip);
    REQUIRE(proj_x == Catch::Approx(pos_x));
    REQUIRE(proj_y == Catch::Approx(pos_y));
    REQUIRE((recip - geom.DetectorToRecip(proj_x, proj_y)).Length() < 0.00000001f);
    REQUIRE(std::fabs(geom.DistFromEwaldSphere(recip)) < 4e-4);
}

TEST_CASE("DiffractionGeometry_Phi","") {
    DiffractionExperiment x(DetJF4M());
    x.DetectorDistance_mm(75).IncidentEnergy_keV(WVL_1A_IN_KEV);
    x.BeamX_pxl(1000).BeamY_pxl(1000);
    DiffractionGeometry geom = x.GetDiffractionGeometry();

    CHECK(geom.Phi_rad(2000, 1000) * (180.0 / M_PI) == Catch::Approx(0.0));
    CHECK(geom.Phi_rad(2000, 0) * (180.0 / M_PI) == Catch::Approx(315.0f));
    CHECK(geom.Phi_rad(1000, 0) * (180.0 / M_PI) == Catch::Approx(270.0f));
    CHECK(geom.Phi_rad(0, 0) * (180.0 / M_PI) == Catch::Approx(225.0f));
    CHECK(geom.Phi_rad(0, 1000) * (180.0 / M_PI) == Catch::Approx(180.0f));
    CHECK(geom.Phi_rad(1000, 2000) * (180.0 / M_PI) == Catch::Approx(90.f));
    CHECK(geom.Phi_rad(2000, 2000) * (180.0 / M_PI) == Catch::Approx(45.0f));
}

TEST_CASE("DiffractionGeometry_Cos2Theta","") {
    DiffractionExperiment x(DetJF4M());
    x.DetectorDistance_mm(75).IncidentEnergy_keV(WVL_1A_IN_KEV);
    x.BeamX_pxl(1000).BeamY_pxl(1000);
    DiffractionGeometry geom = x.GetDiffractionGeometry();

    // det distance == 1000 pixel
    // theta = 30 deg
    // tan(2 * theta) = sqrt(3)
    REQUIRE(cosf(geom.TwoTheta_rad(1000, 1000 * (1.0 + sqrt(3)))) == Catch::Approx(0.5f));
}

TEST_CASE("DiffractionGeometry_PxlToRes","") {
    DiffractionExperiment x(DetJF4M());
    x.DetectorDistance_mm(75).IncidentEnergy_keV(WVL_1A_IN_KEV);
    DiffractionGeometry geom = x.GetDiffractionGeometry();

    // sin(theta) = 1/2
    // theta = 30 deg
    // tan(2 * theta) = sqrt(3)
    REQUIRE(geom.PxlToRes( 0, 1000 * sqrt(3)) == Catch::Approx(1.0));

    // sin(theta) = 1/4
    // theta = 14.47 deg
    // tan(2 * theta) = 0.55328333517

    REQUIRE(geom.PxlToRes(1000 * 0.55328333517 * cosf(1), 1000 * 0.55328333517 * sinf(1)) == Catch::Approx(2.0));
}


TEST_CASE("DiffractionGeometry_ResToPxl","") {
    DiffractionExperiment x(DetJF4M());
    x.DetectorDistance_mm(75).IncidentEnergy_keV(WVL_1A_IN_KEV);
    DiffractionGeometry geom = x.GetDiffractionGeometry();

    // sin(theta) = 1/2
    // theta = 30 deg
    // tan(2 * theta) = sqrt(3)
    REQUIRE(geom.ResToPxl(1.0) == Catch::Approx(1000 * sqrt(3)));

    // sin(theta) = 1/4
    // theta = 14.47 deg
    // tan(2 * theta) = 0.55328333517
    REQUIRE(geom.ResToPxl(2.0) == Catch::Approx(1000 * 0.55328333517));
}

TEST_CASE("DiffractionGeometry_SolidAngleCorrection","") {
    DiffractionExperiment x;
    x.IncidentEnergy_keV(WVL_1A_IN_KEV);
    x.BeamX_pxl(1000).BeamY_pxl(1000).DetectorDistance_mm(75);
    DiffractionGeometry geom = x.GetDiffractionGeometry();

    // 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","") {
    DiffractionExperiment x;
    x.IncidentEnergy_keV(WVL_1A_IN_KEV);
    x.BeamX_pxl(1000).BeamY_pxl(1000).DetectorDistance_mm(75);

    DiffractionGeometry geom = x.GetDiffractionGeometry();

    // Circular polarization 0.5*(1+cos(2theta)^2)
    x.PolarizationFactor(0);
    REQUIRE(geom.CalcAzIntPolarizationCorr(1000 * (1.0 + sqrt(3)), 1000, 0) == Catch::Approx(0.5f * (1 + 0.5f * 0.5f)));
    REQUIRE(geom.CalcAzIntPolarizationCorr(1000, 1000 * (1.0 + sqrt(3)), 0) == Catch::Approx(0.5f * (1 + 0.5f * 0.5f)));

    // Horizontal polarization
    x.PolarizationFactor(1);

    // No correction in vertical direction
    REQUIRE(geom.CalcAzIntPolarizationCorr(1000, 1000 * (1.0 + sqrt(3)), 1) == Catch::Approx(1.0f));
    REQUIRE(geom.CalcAzIntPolarizationCorr(1000, 1000 * (1.0 - sqrt(3)), 1) == Catch::Approx(1.0f));

    // cos(2*theta)^2 in horizontal direction
    REQUIRE(geom.CalcAzIntPolarizationCorr(1000 * (1.0 + sqrt(3)), 1000, 1) == Catch::Approx(0.5f * 0.5f));
    REQUIRE(geom.CalcAzIntPolarizationCorr(1000 * (1.0 - sqrt(3)), 1000, 1) == Catch::Approx(0.5f * 0.5f));
}

TEST_CASE("DiffractionGeometry_AngleFromEwaldSphere") {
    DiffractionGeometry geom;
    geom.Wavelength_A(1.0);

    // Center of Ewald sphere == (0,0,-1)

    // Points on Ewald sphere
    REQUIRE(geom.AngleFromEwaldSphere_deg(Coord(1, 0, -1)) == 0.0f);
    REQUIRE(geom.AngleFromEwaldSphere_deg(Coord(1.0f / sqrtf(2.0f), 1.0f / sqrtf(2.0f), -1)) == 0.0f);

    REQUIRE(geom.AngleFromEwaldSphere_deg(Coord(1, 0, 1)) == Catch::Approx(90.0f));
    REQUIRE(geom.AngleFromEwaldSphere_deg(Coord(-sqrtf(2.0f), 0, 0)) == Catch::Approx(45.0f));
    REQUIRE(geom.AngleFromEwaldSphere_deg(Coord(-sqrtf(3.0f), 0, 0)) == Catch::Approx(60.0f));

    float cos_1deg = cosf(1.0f * M_PI / 180.0f);
    float sin_1deg = sinf(1.0f * M_PI / 180.0f);

    REQUIRE(fabsf(geom.AngleFromEwaldSphere_deg((Coord(cos_1deg - sin_1deg, 0, -(cos_1deg + sin_1deg)))) - 1.0f) < 0.0005);

    // Cannot be rotated to fit into the Ewald sphere
    REQUIRE(isnanf(geom.AngleFromEwaldSphere_deg(Coord(0, 0, 1))));
}

TEST_CASE("DiffractionGeometry_AngleFromEwaldSphere_Wvl2A") {
    DiffractionGeometry geom;
    geom.BeamX_pxl(1000).BeamY_pxl(1000).DetectorDistance_mm(100).Wavelength_A(2.0);

    CHECK(geom.AngleFromEwaldSphere_deg(geom.DetectorToRecip(300,300)) < 0.05f);
    CHECK(geom.AngleFromEwaldSphere_deg(geom.DetectorToRecip(200,1700)) < 0.05f);
    CHECK(geom.AngleFromEwaldSphere_deg(geom.DetectorToRecip(1200,1800)) < 0.05f);
    CHECK(geom.AngleFromEwaldSphere_deg(geom.DetectorToRecip(1500,100)) < 0.05f);
}

TEST_CASE("DiffractionGeometry_ProjectToEwaldSphere") {
    DiffractionGeometry geom;
    geom.BeamX_pxl(1000).BeamY_pxl(437).DetectorDistance_mm(100).Wavelength_A(2.0);
    Coord p0 = geom.DetectorToRecip(300,300);
    Coord p1 = geom.ProjectToEwaldSphere(p0);
    REQUIRE(p0.x == Catch::Approx(p1.x));
    REQUIRE(p0.y == Catch::Approx(p1.y));
    REQUIRE(p0.z == Catch::Approx(p1.z));

    Coord p2 = Coord(1,0,0);

    REQUIRE(std::fabs(geom.DistFromEwaldSphere(p2) > 0.01));
    REQUIRE(std::fabs(geom.DistFromEwaldSphere(geom.ProjectToEwaldSphere(p2))) < 0.0001);
}

TEST_CASE("DiffractionGeometry_DirectBeam") {
    DiffractionGeometry geom;
    geom.Wavelength_A(1.0);
    geom.BeamX_pxl(1230).BeamY_pxl(1450);

    auto [x, y] = geom.GetDirectBeam_pxl();
    REQUIRE(x == Catch::Approx(1230.0f));
    REQUIRE(y == Catch::Approx(1450.0f));
}

TEST_CASE("DiffractionGeometry_DirectBeam_RotZ") {
    DiffractionGeometry geom;
    geom.Wavelength_A(1.0);
    geom.BeamX_pxl(1230).BeamY_pxl(1450);
    geom.PoniRot3_rad(-M_PI_2);

    auto [x, y] = geom.GetDirectBeam_pxl();
    REQUIRE(x == Catch::Approx(1230.0f));
    REQUIRE(y == Catch::Approx(1450.0f));
}

TEST_CASE("DiffractionGeometry_DirectBeam_RotY") {
    DiffractionGeometry geom;
    geom.Wavelength_A(1.0);
    geom.DetectorDistance_mm(100);
    geom.PixelSize_mm(1.0);
    geom.BeamX_pxl(1230).BeamY_pxl(1450);
    geom.PoniRot2_rad(-M_PI_4); // 45 deg rotation

    auto [x, y] = geom.GetDirectBeam_pxl();
    CHECK(x == Catch::Approx(1230.0f)); // no Change for X
    CHECK(y >1450.0f);
}

TEST_CASE("DiffractionGeometry_PONI","") {
/*
poni_version: 2
Detector: Eiger4M
Detector_config: {}
Distance: 1.0
Poni1: 0.075
Poni2: 0.150
Rot1: 0.0
Rot2: 0.0
Rot3: 0.0
Wavelength: 1e-10
 */

// PyFAI uses nm^-1 for Q?
// The beam centre is Poni/pixel_size - 0.5 in every PONI test here: our coordinates are pixel-centred
// (0.0 is the centre of the first pixel) while pyFAI measures from the edge of the sensor and puts the
// centre of pixel i at (i + 0.5) * pixel size - see docs/DETECTOR_GEOMETRY.md. So 0.150 m / 75 um gives
// 1999.5, not 2000. With the half pixel the reference values below are reproduced to float precision;
// without it every one of them is out by 2.6e-3 nm^-1, which the old 1e-2 tolerance hid.
    DiffractionExperiment x(DetJF4M());
    x.DetectorDistance_mm(1000).BeamX_pxl(1999.5).BeamY_pxl(999.5).IncidentEnergy_keV(WVL_1A_IN_KEV);
    DiffractionGeometry geom = x.GetDiffractionGeometry();

    float diff_800_400 = fabs(geom.PxlToQ( 800,400)*10.0 - 6.295358803860941);
    float diff_400_800 = fabs(geom.PxlToQ( 400,800)*10.0 - 7.554628215027982);
    float diff_1300_2000 = fabs(geom.PxlToQ( 1300,2000)*10.0 - 5.73479724964891);

    REQUIRE(diff_800_400 < 1e-4);
    REQUIRE(diff_400_800 < 1e-4);
    REQUIRE(diff_1300_2000 < 1e-4);
}

TEST_CASE("DiffractionGeometry_PONI_phi","") {
/*
poni_version: 2
Detector: Eiger4M
Detector_config: {}
Distance: 1.0
Poni1: 0.075
Poni2: 0.150
Rot1: 0.0
Rot2: 0.0
Rot3: 0.0
Wavelength: 1e-10
 */

// PyFAI uses nm^-1 for Q?
    DiffractionExperiment x(DetJF4M());
    x.DetectorDistance_mm(1000).BeamX_pxl(1999.5).BeamY_pxl(999.5).IncidentEnergy_keV(WVL_1A_IN_KEV);
    DiffractionGeometry geom = x.GetDiffractionGeometry();

    float phi_2000_0 = fabs(geom.Phi_rad(2000,0) - 2 * M_PI + 1.5702959937284997);
    float phi_2000_2000 = fabs(geom.Phi_rad(2000,2000) - 1.5702964938446844);
    float phi_0_1000 = fabs(geom.Phi_rad(0,1000) - 3.1413425992666903);
    float phi_2000_1300 = fabs(geom.Phi_rad(1300,2000) - 2.1809518509415025);

    CHECK(phi_2000_0 < 1e-4);
    CHECK(phi_2000_2000 < 1e-4);
    CHECK(phi_0_1000 < 1e-4);
    CHECK(phi_2000_1300 < 1e-4);
}


TEST_CASE("DiffractionGeometry_PONI_phi_rot3","") {
/*
poni_version: 2
Detector: Eiger4M
Detector_config: {}
Distance: 1.0
Poni1: 0.075
Poni2: 0.150
Rot1: 0.0
Rot2: 0.0
Rot3: 0.5
Wavelength: 1e-10
 */

// PyFAI uses nm^-1 for Q?
    DiffractionExperiment x(DetJF4M());
    x.DetectorDistance_mm(1000).BeamX_pxl(1999.5).BeamY_pxl(999.5).IncidentEnergy_keV(WVL_1A_IN_KEV)
            .PoniRot3_rad(0.5);
    DiffractionGeometry geom = x.GetDiffractionGeometry();
    REQUIRE(geom.GetPoniRot3_rad() == Catch::Approx(0.5f));

    float phi_800_400 = fabs(geom.Phi_rad(800,400) - 3.105073518019684);
    float phi_2000_1300 = fabs(geom.Phi_rad(1300,2000) - 1.6809518509415027);

    CHECK(phi_800_400 < 1e-4);
    CHECK(phi_2000_1300 < 1e-4);
}


TEST_CASE("DiffractionGeometry_PONI_phi_rot1_rot2_rot3","") {
/*
poni_version: 2
Detector: Eiger4M
Detector_config: {}
Distance: 1.0
Poni1: 0.075
Poni2: 0.150
Rot1: 0.2
Rot2: 0.1
Rot3: 0.5
Wavelength: 1e-10
 */

// PyFAI uses nm^-1 for Q?
    DiffractionExperiment x(DetJF4M());
    x.DetectorDistance_mm(1000).BeamX_pxl(1999.5).BeamY_pxl(999.5).IncidentEnergy_keV(WVL_1A_IN_KEV)
            .PoniRot1_rad(0.2).PoniRot2_rad(-0.1).PoniRot3_rad(0.5);
    DiffractionGeometry geom = x.GetDiffractionGeometry();

    REQUIRE(geom.GetPoniRot1_rad() == Catch::Approx(0.2f));
    REQUIRE(geom.GetPoniRot2_rad() == Catch::Approx(-0.1f));
    REQUIRE(geom.GetPoniRot3_rad() == Catch::Approx(0.5f));

    float phi_800_400 = fabs(geom.Phi_rad(800,400) - 2 * M_PI + 1.4175001633470816);
    float phi_2000_1300 = fabs(geom.Phi_rad(1300,2000) - 2 * M_PI + 0.6630282166663707);

    CHECK(phi_800_400 < 1e-4);
    CHECK(phi_2000_1300 < 1e-4);
}

TEST_CASE("DiffractionGeometry_PONI_rot1","") {
/*
poni_version: 2
Detector: Eiger4M
Detector_config: {}
Distance: 1.0
Poni1: 0.075
Poni2: 0.150
Rot1: 0.2
Rot2: 0.0
Rot3: 0.0
Wavelength: 1e-10
 */

// PyFAI uses nm^-1 for Q?
    DiffractionExperiment x(DetJF4M());
    x.DetectorDistance_mm(1000).BeamX_pxl(1999.5).BeamY_pxl(999.5).IncidentEnergy_keV(WVL_1A_IN_KEV);
    DiffractionGeometry geom = x.GetDiffractionGeometry();
    geom.PoniRot1_rad(0.2);

    float diff_800_400 = fabs(geom.PxlToQ( 800,400)*10.0 - 7.471276390173706);
    float diff_400_800 = fabs(geom.PxlToQ( 400,800)*10.0 - 5.148411999405654);
    float diff_1300_2000 = fabs(geom.PxlToQ( 1300,2000)*10.0 - 10.37635963741911);

    CHECK(diff_800_400 < 1e-4);
    CHECK(diff_400_800 < 1e-4);
    CHECK(diff_1300_2000 < 1e-4);
}


TEST_CASE("DiffractionGeometry_PONI_rot1_rot2","") {
/*
poni_version: 2
Detector: Eiger4M
Detector_config: {}
Distance: 1.0
Poni1: 0.075
Poni2: 0.150
Rot1: 0.2
Rot2: 0.1
Rot3: 0.0
Wavelength: 1e-10
 */

// PyFAI uses nm^-1 for Q?
    DiffractionExperiment x(DetJF4M());
    x.DetectorDistance_mm(1000).BeamX_pxl(1999.5).BeamY_pxl(999.5).IncidentEnergy_keV(WVL_1A_IN_KEV);
    DiffractionGeometry geom = x.GetDiffractionGeometry();
    geom.PoniRot1_rad(0.2).PoniRot2_rad(-0.1);

    float diff_800_400 = fabs(geom.PxlToQ( 800,400)*10.0 - 11.412737079654118);
    float diff_400_800 = fabs(geom.PxlToQ( 400,800)*10.0 - 8.805012278158177);
    float diff_1300_2000 = fabs(geom.PxlToQ( 1300,2000)*10.0 - 9.363455481328781);

    CHECK(diff_800_400 < 1e-4);
    CHECK(diff_400_800 < 1e-4);
    CHECK(diff_1300_2000 < 1e-4);
}

TEST_CASE("DiffractionGeometry_PyFAI_Solid_angle","") {
/*
poni_version: 2
Detector: Eiger4M
Detector_config: {}
Distance: 0.2
Poni1: 0.075
Poni2: 0.150
Rot1: 0.0
Rot2: 0.0
Rot3: 0.0
Wavelength: 1e-10
 */

// 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(1999.5).BeamY_pxl(999.5).IncidentEnergy_keV(WVL_1A_IN_KEV);
    DiffractionGeometry geom = x.GetDiffractionGeometry();

    float diff_100_100 = fabs(geom.CalcAzIntSolidAngleCorr( 100,100) - 0.4844596502755233);
    CHECK(diff_100_100 < 1e-5);

    float diff_400_800 = fabs(geom.CalcAzIntSolidAngleCorr( 400,800)- 0.6267921080721112);
    CHECK(diff_400_800 < 1e-5);
}

TEST_CASE("ResPhiToPxl") {
    DiffractionExperiment x(DetJF4M());
    x.DetectorDistance_mm(75).IncidentEnergy_keV(WVL_1A_IN_KEV);
    DiffractionGeometry geom = x.GetDiffractionGeometry();

    auto out = geom.ResPhiToPxl(1.0, 0);
    CHECK(geom.PxlToRes(out.first, out.second) == Catch::Approx(1.0));
    CHECK(fabs(geom.Phi_rad(out.first, out.second)) < 0.001 );

    out = geom.ResPhiToPxl(1.0, M_PI);
    CHECK(geom.PxlToRes(out.first, out.second) == Catch::Approx(1.0));
    CHECK(fabs(geom.Phi_rad(out.first, out.second) - M_PI) < 0.001 );

    out = geom.ResPhiToPxl(2.0, 0.7567);
    CHECK(geom.PxlToRes(out.first, out.second) == Catch::Approx(2.0));
    CHECK(fabs(geom.Phi_rad(out.first, out.second) - 0.7567) < 0.001 );
}

TEST_CASE("ResPhiToPxl_poni_rot") {
    DiffractionExperiment x(DetJF4M());
    x.DetectorDistance_mm(75).IncidentEnergy_keV(WVL_1A_IN_KEV);
    DiffractionGeometry geom = x.GetDiffractionGeometry();
    geom.PoniRot3_rad(0.5).PoniRot2_rad(-0.1).PoniRot2_rad(0.3);

    auto out = geom.ResPhiToPxl(1.0, 0);
    CHECK(geom.PxlToRes(out.first, out.second) == Catch::Approx(1.0));
    CHECK(fabs(geom.Phi_rad(out.first, out.second)) < 0.001 );

    out = geom.ResPhiToPxl(1.0, M_PI);
    CHECK(geom.PxlToRes(out.first, out.second) == Catch::Approx(1.0));
    CHECK(fabs(geom.Phi_rad(out.first, out.second) - M_PI) < 0.001 );

    out = geom.ResPhiToPxl(2.0, 0.7567);
    CHECK(geom.PxlToRes(out.first, out.second) == Catch::Approx(2.0));
    CHECK(fabs(geom.Phi_rad(out.first, out.second) - 0.7567) < 0.001 );
}

TEST_CASE("DiffractionGeometry_DetectorToRecip_RecipToDetector_tilted") {
    // Verify roundtrip consistency with non-zero rot1/rot2
    DiffractionGeometry geom;
    geom.BeamX_pxl(1000).BeamY_pxl(1000).DetectorDistance_mm(150)
        .PixelSize_mm(0.075).Wavelength_A(1.0)
        .PoniRot1_rad(0.05).PoniRot2_rad(-0.03);

    // Test multiple points across the detector
    std::vector<std::pair<float, float>> test_points = {
        {500, 500}, {1500, 500}, {500, 1500}, {1500, 1500},
        {800, 1200}, {1200, 800}, {300, 1700}, {1700, 300}
    };

    for (const auto& [x, y] : test_points) {
        Coord recip = geom.DetectorToRecip(x, y);
        auto [proj_x, proj_y] = geom.RecipToDetector(recip);

        CHECK(proj_x == Catch::Approx(x).margin(0.001));
        CHECK(proj_y == Catch::Approx(y).margin(0.001));
    }
}

TEST_CASE("DiffractionGeometry_PONI_matrix_consistency") {
    // Verify that the PONI rotation matrix gives consistent results
    // when used for both forward and inverse transformations
    DiffractionGeometry geom;
    geom.BeamX_pxl(1000).BeamY_pxl(1000).DetectorDistance_mm(100)
        .PixelSize_mm(0.075).Wavelength_A(1.0)
        .PoniRot1_rad(0.04).PoniRot2_rad(-0.025);

    const auto& poni_rot = geom.GetDetectorMatrix();
    const auto poni_rot_T = poni_rot.transpose();

    // Test: poni_rot * poni_rot^T should be identity (orthogonal matrix)
    for (int i = 0; i < 3; ++i) {
        for (int j = 0; j < 3; ++j) {
            Coord ei, ej;
            ei[i] = 1.0f;
            ej[j] = 1.0f;
            float expected = (i == j) ? 1.0f : 0.0f;
            CHECK((poni_rot * (poni_rot_T * ej))[i] == Catch::Approx(expected).margin(1e-6));
        }
    }

    // Test: S0 vector transformation
    Coord S0 = geom.GetScatteringVector();
    // For beam along z, S0 = (0, 0, 1/λ)
    CHECK(S0.x == Catch::Approx(0.0f));
    CHECK(S0.y == Catch::Approx(0.0f));
    CHECK(S0.z == Catch::Approx(1.0f));
}
// Cross-check of a TILTED detector against two independent implementations, pyFAI and DIALS/dxtbx.
//
// Every other geometry test here is either self-consistent (round trips) or exercises one angle at a
// time. This one pins all three PONI angles at once, non-zero and of mixed sign, against reference
// positions computed outside Jungfraujoch. That matters because the errors this guards against are
// second order: a wrong composition order or a swapped axis is invisible unless two angles are
// non-zero simultaneously, and a wrong pivot is invisible to anything that only checks directions.
//
// HOW TO REGENERATE THE NUMBERS
//
// pyFAI (`pip install pyFAI`), which is an independent implementation of the PONI convention:
//
//     from pyFAI.geometry import Geometry
//     from pyFAI.detectors import Detector
//     px = 75e-6
//     det = Detector(pixel1=px, pixel2=px, max_shape=(2164, 2030))
//     g = Geometry(dist=0.150, poni1=1275*px + px/2, poni2=1000*px + px/2,
//                  rot1=0.05, rot2=+0.03, rot3=0.02,      # (+rot1, -rot2, +rot3); see WritePoniFile
//                  detector=det, wavelength=1e-10)
//     t3, t1, t2 = g.calc_pos_zyx(d1=[y], d2=[x])         # metres, pyFAI's own axes
//     lab_mm = (t2*1e3, t1*1e3, t3*1e3)                   # pyFAI (t1,t2,t3) -> our (x,y,z)
//
// The half pixel in poni1/poni2 is the origin convention (docs/DETECTOR_GEOMETRY.md): our beam
// centre is pixel-centred, pyFAI measures from the sensor edge.
//
// DIALS: write a master, patch this geometry into it, and read the panel back.
//
//     source /opt/dials-v3-27-0/dials_env.sh
//     build/tools/jfjoch_hdf5_test <input.h5> -n1 -S -o g          # writes g_master.h5
//     # with h5py, set /entry/instrument/detector/{beam_center_x,beam_center_y,distance},
//     # transformations/{rot1,rot2,rot3}, and recompute transformations/translation - both its
//     # magnitude and its @vector - as {bx*px, by*px, distance} normalised, since the writer
//     # derives it from the beam centre and distance.
//     p = ExperimentListFactory.from_filenames(['g_master.h5'])[0].detector[0]
//     lab = p.get_origin() + x*px_mm*p.get_fast_axis() + y*px_mm*p.get_slow_axis()
//
// Use get_origin()/get_fast_axis()/get_slow_axis() as above, NOT get_pixel_lab_coord(): that applies
// a parallax correction from the sensor thickness and material which DiffractionGeometry does not
// model, and it costs ~0.1 mm at the detector edge - enough to look like a geometry error.
//
// DIALS reports in the imgCIF frame, which is ours turned 180 degrees about x (diag(1,-1,-1)) - a
// proper rotation, not a mirror. The test applies that mapping, so it pins the frame relation too.
TEST_CASE("DiffractionGeometry_Tilted_vs_PyFAI_and_DIALS", "[DiffractionGeometry]") {
    DiffractionGeometry geom;
    geom.BeamX_pxl(1000.0f).BeamY_pxl(1275.0f).DetectorDistance_mm(150.0f)
        .PixelSize_mm(0.075f).Wavelength_A(1.0f)
        .PoniRot1_rad(0.05f).PoniRot2_rad(-0.03f).PoniRot3_rad(0.02f);

    struct Reference {
        int x, y;
        float pyfai[3];   // our frame:   x, y, z   [mm]
        float dials[3];   // imgCIF frame: x, y, z  [mm]
    };

    const std::vector<Reference> reference = {
        {    0,    0, {-69.399541334f, -98.819975327f, 150.623559791f},
                      {-69.399544982f,  98.819979800f, -150.623559832f}},
        { 2029, 2163, { 85.802269836f,  60.488193357f, 147.887421982f},
                      { 85.802273560f, -60.488196450f, -147.887421893f}},
        { 1000, 1275, {  7.405508016f,  -4.642730847f, 149.745128473f},
                      {  7.405508016f,   4.642730847f, -149.745128473f}},
        {  300, 1800, {-44.232874953f,  35.676608756f, 153.548927011f},
                      {-44.232877406f, -35.676610671f, -153.548927191f}},
        { 1700,  400, { 58.519162201f, -71.195011374f, 145.153948055f},
                      { 58.519164629f,  71.195014535f, -145.153947836f}},
    };

    // 2 um, i.e. 1/37 of a pixel. The references agree with each other to ~4e-6 mm; the margin is
    // set by float32 rounding in DiffractionGeometry and in the HDF5 file the DIALS values came from.
    const double margin = 2e-3;

    for (const auto &r: reference) {
        const Coord lab = geom.LabCoord(static_cast<float>(r.x), static_cast<float>(r.y));

        CHECK(lab.x == Catch::Approx(r.pyfai[0]).margin(margin));
        CHECK(lab.y == Catch::Approx(r.pyfai[1]).margin(margin));
        CHECK(lab.z == Catch::Approx(r.pyfai[2]).margin(margin));

        CHECK(lab.x == Catch::Approx( r.dials[0]).margin(margin));
        CHECK(lab.y == Catch::Approx(-r.dials[1]).margin(margin));
        CHECK(lab.z == Catch::Approx(-r.dials[2]).margin(margin));
    }
}

// ---------------------------------------------------------------------------------------------
// PONI angles <-> detector axis vectors, and the discrete image orientation
// ---------------------------------------------------------------------------------------------

namespace {
    void CheckSameMatrix(const RotMatrix &a, const RotMatrix &b, float margin = 1e-6f) {
        for (int i = 0; i < 3; i++) {
            const Coord ca = a.Column(i), cb = b.Column(i);
            CHECK(ca.x == Catch::Approx(cb.x).margin(margin));
            CHECK(ca.y == Catch::Approx(cb.y).margin(margin));
            CHECK(ca.z == Catch::Approx(cb.z).margin(margin));
        }
    }
}

TEST_CASE("PoniAngles_matrix_roundtrip") {
    const float half_pi = static_cast<float>(PI) / 2.0f;
    // rot1 and rot3 are recovered by atan2, so the branch cut at +-pi makes an angle comparison there
    // meaningless (+pi and -pi are the same rotation). The matrix comparison below covers it; the
    // angle comparison uses everything else, including the exact multiples of 90 degrees that are not
    // on the cut.
    const std::vector<float> angles = {0.0f, 0.01f, -0.03f, 0.7f, -1.2f, half_pi, -half_pi};

    for (float rot1: angles) {
        for (float rot3: angles) {
            for (float rot2: {0.0f, 0.02f, -0.4f, 1.0f, -1.4f}) {
                float r1, r2, r3;
                PoniAnglesFromMatrix(PoniRotMatrix(rot1, rot2, rot3), r1, r2, r3);
                CHECK(r1 == Catch::Approx(rot1).margin(1e-5));
                CHECK(r2 == Catch::Approx(rot2).margin(1e-5));
                CHECK(r3 == Catch::Approx(rot3).margin(1e-5));
                CheckSameMatrix(PoniRotMatrix(r1, r2, r3), PoniRotMatrix(rot1, rot2, rot3));
            }
        }
    }

    // A half turn is on the atan2 branch cut, so only the matrix can be required to come back.
    for (float rot1: {static_cast<float>(PI), -static_cast<float>(PI)}) {
        float r1, r2, r3;
        PoniAnglesFromMatrix(PoniRotMatrix(rot1, 0.1f, 0.2f), r1, r2, r3);
        CheckSameMatrix(PoniRotMatrix(r1, r2, r3), PoniRotMatrix(rot1, 0.1f, 0.2f));
    }

    // Gimbal lock: at rot2 = +-90 degrees only rot1 +- rot3 is determined, and the convention is to
    // put it all into rot1. A triple that already has rot3 = 0 therefore comes back unchanged, and
    // the matrix comes back whatever rot3 was.
    for (float rot2: {half_pi, -half_pi}) {
        for (float rot1: {0.0f, 0.3f, -1.2f}) {
            float r1, r2, r3;
            PoniAnglesFromMatrix(PoniRotMatrix(rot1, rot2, 0.0f), r1, r2, r3);
            CHECK(r1 == Catch::Approx(rot1).margin(1e-5));
            CHECK(r2 == Catch::Approx(rot2).margin(1e-5));
            CHECK(r3 == 0.0f);

            PoniAnglesFromMatrix(PoniRotMatrix(rot1, rot2, 0.4f), r1, r2, r3);
            CheckSameMatrix(PoniRotMatrix(r1, r2, r3), PoniRotMatrix(rot1, rot2, 0.4f));
        }
    }
}

TEST_CASE("DetectorAxes_roundtrip") {
    for (int64_t quarter_turns = 0; quarter_turns < 4; quarter_turns++) {
        for (bool mirror: {false, true}) {
            for (float rot1: {0.0f, 0.05f, -0.9f}) {
                for (float rot2: {0.0f, -0.03f, 1.1f}) {
                    for (float rot3: {0.0f, 0.2f, -1.5f}) {
                        DiffractionGeometry geom;
                        geom.Orientation(DetectorOrientation(mirror, quarter_turns))
                            .PoniRot1_rad(rot1).PoniRot2_rad(rot2).PoniRot3_rad(rot3);

                        const Coord fast = geom.GetFastAxis();
                        const Coord slow = geom.GetSlowAxis();
                        const RotMatrix before = geom.GetDetectorMatrix();

                        // Feeding the two axes straight back must not move anything.
                        DiffractionGeometry from_axes;
                        from_axes.Orientation(DetectorOrientation(mirror, quarter_turns))
                                 .DetectorAxes(fast, slow);
                        CheckSameMatrix(from_axes.GetDetectorMatrix(), before, 1e-5f);
                        CHECK(from_axes.GetPoniRot1_rad() == Catch::Approx(rot1).margin(1e-5));
                        CHECK(from_axes.GetPoniRot2_rad() == Catch::Approx(rot2).margin(1e-5));
                        CHECK(from_axes.GetPoniRot3_rad() == Catch::Approx(rot3).margin(1e-5));
                    }
                }
            }
        }
    }
}

TEST_CASE("DetectorOrientation_identity_is_todays_geometry") {
    DiffractionGeometry with_default;
    with_default.PoniRot1_rad(0.04f).PoniRot2_rad(-0.02f).PoniRot3_rad(0.11f);

    DiffractionGeometry with_identity;
    with_identity.Orientation(DetectorOrientation(false, 0))
                 .PoniRot1_rad(0.04f).PoniRot2_rad(-0.02f).PoniRot3_rad(0.11f);

    // Bit for bit: the discrete part must cost existing data nothing.
    CheckSameMatrix(with_identity.GetDetectorMatrix(), with_default.GetDetectorMatrix(), 0.0f);
    CheckSameMatrix(with_default.GetDetectorMatrix(), PoniRotMatrix(0.04f, -0.02f, 0.11f), 0.0f);
    CHECK(with_default.GetOrientation().IsIdentity());
}

TEST_CASE("DetectorOrientation_maps_the_detector_plane") {
    // Untilted, so the lab coordinate of a pixel is the discrete orientation applied to its offset
    // from the PONI, in mm.
    auto make = [](bool mirror, int64_t quarter_turns) {
        DiffractionGeometry g;
        g.BeamX_pxl(100).BeamY_pxl(200).DetectorDistance_mm(100).PixelSize_mm(0.1f)
         .Orientation(DetectorOrientation(mirror, quarter_turns));
        return g;
    };

    // One pixel along the fast direction is 0.1 mm from the PONI.
    const Coord fast_step = make(false, 0).LabCoord(101, 200) - make(false, 0).LabCoord(100, 200);
    CHECK(fast_step.x == Catch::Approx(0.1).margin(1e-6));
    CHECK(fast_step.y == Catch::Approx(0.0).margin(1e-6));

    // A quarter turn about the beam takes the fast direction to lab +y ...
    CHECK(make(false, 1).GetFastAxis().y == Catch::Approx(1.0).margin(1e-6));
    // ... and the slow direction to lab -x.
    CHECK(make(false, 1).GetSlowAxis().x == Catch::Approx(-1.0).margin(1e-6));
    // A mirror in Y leaves the fast direction alone and reverses the slow one.
    CHECK(make(true, 0).GetFastAxis().x == Catch::Approx(1.0).margin(1e-6));
    CHECK(make(true, 0).GetSlowAxis().y == Catch::Approx(-1.0).margin(1e-6));
    // Two quarter turns is a half turn.
    CHECK(make(false, 2).GetFastAxis().x == Catch::Approx(-1.0).margin(1e-6));
    CHECK(make(false, 2).GetSlowAxis().y == Catch::Approx(-1.0).margin(1e-6));

    // Every orientation is orthogonal, and improper exactly when it mirrors.
    for (int64_t k = 0; k < 4; k++)
        for (bool mirror: {false, true}) {
            const DetectorOrientation o(mirror, k);
            CheckSameMatrix(o.Matrix() * o.Matrix().transpose(), RotMatrix(), 1e-6f);
            const Coord expected_normal = mirror ? -(o.Matrix().Column(0) % o.Matrix().Column(1))
                                                 : (o.Matrix().Column(0) % o.Matrix().Column(1));
            CheckSameMatrix(RotMatrix(o.Matrix().Column(0), o.Matrix().Column(1), expected_normal),
                            o.Matrix(), 1e-6f);
        }
}

TEST_CASE("DetectorOrientation_preserves_radius_and_solid_angle") {
    // Both generators are signed permutations of (u, v), so the distance from the PONI - and with it
    // the solid-angle correction, the resolution of a ring and every radius-only consumer - cannot
    // move. This is why most of the pipeline needs no change.
    const float ref = [] {
        DiffractionGeometry g;
        g.BeamX_pxl(500).BeamY_pxl(700).DetectorDistance_mm(120).PixelSize_mm(0.075f);
        return g.CalcAzIntSolidAngleCorr(823, 311);
    }();

    for (int64_t k = 0; k < 4; k++)
        for (bool mirror: {false, true}) {
            DiffractionGeometry g;
            g.BeamX_pxl(500).BeamY_pxl(700).DetectorDistance_mm(120).PixelSize_mm(0.075f)
             .PoniRot1_rad(0.03f).PoniRot2_rad(-0.02f)
             .Orientation(DetectorOrientation(mirror, k));
            CHECK(g.CalcAzIntSolidAngleCorr(823, 311) == Catch::Approx(ref).margin(1e-7));
        }
}

TEST_CASE("DetectorOrientation_and_polarization") {
    // Polarization depends on the azimuth in the LABORATORY, so what the discrete orientation changes
    // is which pixel lands where. A quarter turn moves a pixel from the polarization plane to across
    // it; a mirror in Y sends phi to -phi and so cannot move it at all.
    auto corr = [](bool mirror, int64_t quarter_turns, float x, float y) {
        DiffractionGeometry g;
        g.BeamX_pxl(500).BeamY_pxl(500).DetectorDistance_mm(100).PixelSize_mm(0.075f)
         .Orientation(DetectorOrientation(mirror, quarter_turns));
        return g.CalcAzIntPolarizationCorr(x, y, 0.99f);
    };

    const float along_x = corr(false, 0, 700, 500);
    const float along_y = corr(false, 0, 500, 700);
    CHECK(along_x != Catch::Approx(along_y));

    CHECK(corr(false, 1, 700, 500) == Catch::Approx(along_y));
    CHECK(corr(true, 0, 700, 500) == Catch::Approx(along_x));
    CHECK(corr(true, 0, 500, 700) == Catch::Approx(along_y));
}

TEST_CASE("DetectorOrientation_recip_roundtrip") {
    for (int64_t k = 0; k < 4; k++)
        for (bool mirror: {false, true}) {
            DiffractionGeometry geom;
            geom.BeamX_pxl(1000).BeamY_pxl(1000).DetectorDistance_mm(150)
                .PixelSize_mm(0.075f).Wavelength_A(1.0f)
                .PoniRot1_rad(0.05f).PoniRot2_rad(-0.03f).PoniRot3_rad(0.2f)
                .Orientation(DetectorOrientation(mirror, k));

            for (const auto &[x, y]: std::vector<std::pair<float, float>>{
                     {500, 500}, {1500, 500}, {500, 1500}, {1200, 800}}) {
                const auto [px, py] = geom.RecipToDetector(geom.DetectorToRecip(x, y));
                CHECK(px == Catch::Approx(x).margin(0.001));
                CHECK(py == Catch::Approx(y).margin(0.001));
            }
        }
}

// A detector swung out on a 2theta arm, which is how chemical crystallography reaches high angle.
// The arm turns the detector about the sample, so the geometry that describes it is the PONI rotation
// and nothing else moves: the distance stays the distance along the detector normal and the beam
// centre stays the point of normal incidence. What DOES move is the direct beam, which is no longer
// at the beam centre - the two coincide only on a detector square to the beam.
TEST_CASE("DiffractionGeometry_TwoThetaArm", "[LinearAlgebra][Coord]") {
    const float two_theta = 30.0f * PI / 180.0f;
    const float distance_mm = 160.0f, pixel_mm = 0.172f, wavelength = 0.6889f;
    const float bx = 740.0f, by = 866.0f;

    DiffractionGeometry geom;
    geom.BeamX_pxl(bx).BeamY_pxl(by).DetectorDistance_mm(distance_mm)
        .PixelSize_mm(pixel_mm).Wavelength_A(wavelength);
    // The arm turns about the internal x axis; a rotation of +2theta about it is rot2 = -2theta.
    geom.PoniRot2_rad(-two_theta);

    // The beam centre pixel is the PONI: still on the detector normal through the sample, and now
    // 2theta away from the beam.
    CHECK(geom.TwoTheta_rad(bx, by) == Catch::Approx(two_theta));
    CHECK(geom.LabCoord(bx, by).Length() == Catch::Approx(distance_mm));
    CHECK(geom.GetNormalAxis() * Coord(0, 0, 1) == Catch::Approx(cosf(two_theta)));
    // The plane turned about x, so the fast axis - along +x - did not move, and the slow one tipped
    // out of the detector plane by the full 2theta.
    CHECK((geom.GetFastAxis() - Coord(1, 0, 0)).Length() < 1e-6f);
    CHECK(geom.GetSlowAxis() * Coord(0, 0, 1) == Catch::Approx(sinf(two_theta)));

    // The direct beam is off the PONI by D*tan(2theta), along the direction the arm swung.
    auto [direct_x, direct_y] = geom.GetDirectBeam_pxl();
    CHECK(direct_x == Catch::Approx(bx));
    CHECK(direct_y == Catch::Approx(by + distance_mm * tanf(two_theta) / pixel_mm));

    // Resolution at the PONI is the Bragg spacing of 2theta, not of a pixel at zero distance from
    // the beam centre - the reason a swung detector reaches so much further than a square-on one.
    CHECK(geom.PxlToRes(bx, by) == Catch::Approx(wavelength / (2.0f * sinf(two_theta / 2.0f))));

    // Round trip through reciprocal space, at the PONI and away from it in both directions.
    const std::vector<std::pair<float, float>> probes =
            {{bx, by}, {bx + 300.0f, by - 500.0f}, {bx - 700.0f, by + 200.0f}};
    for (const auto &[x, y]: probes) {
        auto [back_x, back_y] = geom.RecipToDetector(geom.DetectorToRecip(x, y));
        CHECK(back_x == Catch::Approx(x));
        CHECK(back_y == Catch::Approx(y));
    }
}