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"

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.GetPoniRotMatrix();
    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));
}