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fix: make SBT beam placement frames right-handed #70

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Merged
olantwin merged 1 commit into from
Jul 23, 2026
+5 −5
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fix: make SBT beam placement frames right-handed #70

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10 changes: 5 additions & 5 deletions subsystems/DecayVolume/src/SBTStructureBuilder.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -154,10 +154,10 @@ void placeHBeamInclined(GeoVPhysVol* parent, const GeoMaterial* mat, const SBTCo
nz /= nmag;
}

// Third axis: b = d x n (completes right-handed frame)
const double bx = uy * nz - uz * ny;
const double by = uz * nx - ux * nz;
const double bz = ux * ny - uy * nx;
// Third axis: b = n x d (completes right-handed frame with columns (b, n, d))
const double bx = ny * uz - nz * uy;
const double by = nz * ux - nx * uz;
const double bz = nx * uy - ny * ux;

const double xcm = 0.5 * (x0 + x1);
const double ycm = 0.5 * (y0 + y1);
Expand Down Expand Up @@ -326,7 +326,7 @@ void SBTStructureBuilder::build(GeoVPhysVol* mother, const GeoMaterial* steel, c

GeoTrf::RotationMatrix3D rotMat;
rotMat.col(0) =
Eigen::Vector3d(uy * nz - uz * ny, uz * nx - ux * nz, ux * ny - uy * nx);
Eigen::Vector3d(ny * uz - nz * uy, nz * ux - nx * uz, nx * uy - ny * ux);
rotMat.col(1) = Eigen::Vector3d(nx, ny, nz);
rotMat.col(2) = Eigen::Vector3d(ux, uy, uz);

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