diff --git a/math/genvector/inc/Math/GenVector/VectorUtil.h b/math/genvector/inc/Math/GenVector/VectorUtil.h
index dbd7661c009a4..e4fc0333058d9 100644
--- a/math/genvector/inc/Math/GenVector/VectorUtil.h
+++ b/math/genvector/inc/Math/GenVector/VectorUtil.h
@@ -275,15 +275,16 @@ namespace ROOT {
// rotation and transformations
-
/**
rotation along X axis for a generic vector by an Angle alpha
returning a new vector.
- The only pre requisite on the Vector is that it has to implement the X() , Y() and Z()
+ The only pre requisite on the Vector is that it has to implement the X(), Y() and Z()
and SetXYZ methods.
*/
template <class Vector>
Vector RotateX(const Vector & v, double alpha) {
+ if (std::fmod(alpha, 2 * M_PI) == 0.)
+ return v;
using std::sin;
double sina = sin(alpha);
using std::cos;
@@ -298,11 +299,13 @@ namespace ROOT {
/**
rotation along Y axis for a generic vector by an Angle alpha
returning a new vector.
- The only pre requisite on the Vector is that it has to implement the X() , Y() and Z()
+ The only pre requisite on the Vector is that it has to implement the X(), Y() and Z()
and SetXYZ methods.
*/
template <class Vector>
Vector RotateY(const Vector & v, double alpha) {
+ if (std::fmod(alpha, 2 * M_PI) == 0.)
+ return v;
using std::sin;
double sina = sin(alpha);
using std::cos;
@@ -317,11 +320,13 @@ namespace ROOT {
/**
rotation along Z axis for a generic vector by an Angle alpha
returning a new vector.
- The only pre requisite on the Vector is that it has to implement the X() , Y() and Z()
+ The only pre requisite on the Vector is that it has to implement the X(), Y() and Z()
and SetXYZ methods.
*/
template <class Vector>
Vector RotateZ(const Vector & v, double alpha) {
+ if (std::fmod(alpha, 2 * M_PI) == 0.)
+ return v;
using std::sin;
double sina = sin(alpha);
using std::cos;
@@ -333,6 +338,40 @@ namespace ROOT {
return vrot;
}
+ /**
+ rotation along a custom axis for a generic vector by an Angle alpha (in rad)
+ returning a new vector.
+ The only pre requisite on the Vector is that it has to implement the X(), Y() and Z()
+ and SetXYZ methods.
+ */
+ template <class Vector>
+ Vector Rotate(const Vector &v, double alpha, const Vector &axis)
+ {
+ if (std::fmod(alpha, 2 * M_PI) == 0.)
+ return v;
+ const double ll = std::sqrt(axis.X() * axis.X() + axis.Y() * axis.Y() + axis.Z() * axis.Z());
+ if (ll == 0.)
+ GenVector::Throw("Axis Vector has zero magnitude");
+ const double sa = std::sin(alpha);
+ const double ca = std::cos(alpha);
+ const double dx = axis.X() / ll;
+ const double dy = axis.Y() / ll;
+ const double dz = axis.Z() / ll;
+ // clang-format off
+ const double rot00 = (1 - ca) * dx * dx + ca , rot01 = (1 - ca) * dx * dy - sa * dz, rot02 = (1 - ca) * dx * dz + sa * dy,
+ rot10 = (1 - ca) * dy * dx + sa * dz, rot11 = (1 - ca) * dy * dy + ca , rot12 = (1 - ca) * dy * dz - sa * dx,
+ rot20 = (1 - ca) * dz * dx - sa * dy, rot21 = (1 - ca) * dz * dy + sa * dx, rot22 = (1 - ca) * dz * dz + ca ;
+ // clang-format on
+ const double xX = v.X();
+ const double yY = v.Y();
+ const double zZ = v.Z();
+ const double x2 = rot00 * xX + rot01 * yY + rot02 * zZ;
+ const double y2 = rot10 * xX + rot11 * yY + rot12 * zZ;
+ const double z2 = rot20 * xX + rot21 * yY + rot22 * zZ;
+ Vector vrot;
+ vrot.SetXYZ(x2, y2, z2);
+ return vrot;
+ }
/**
rotation on a generic vector using a generic rotation class.
diff --git a/math/genvector/test/testGenVector.cxx b/math/genvector/test/testGenVector.cxx
index 9a6cb9f210be6..2a73505fd90d1 100644
--- a/math/genvector/test/testGenVector.cxx
+++ b/math/genvector/test/testGenVector.cxx
@@ -466,6 +466,21 @@ int testRotations3D() {
iret |= compare(qr1.Y(), qr2.Y(),"y diff",10 );
iret |= compare(qr1.Z(), qr2.Z(),"z diff",10 );
+ // test TVector3-like Rotate function around some axis by an angle. Test case taken from cwessel:
+ // https://root-forum.cern.ch/t/tvector3-rotate-to-arbitrary-rotation-using-xyzvector/63244/7
+ XYZVector ag(17, -4, -23);
+ double angle = 100;
+ XYZVector axisg(-23.4, 1.7, -0.3);
+ XYZVector rotated = Rotate(ag, angle, axisg);
+ // should be equivalent to:
+ // TVector3 at(17, -4, -23);
+ // TVector3 axist(-23.4, 1.7, -0.3);
+ // at.Rotate(angle, axist);
+ // at.Print();
+ // (17.856456,8.106555,-21.199782)
+ iret |= compare(rotated.X(), 17.856456, "x diff", 1e10);
+ iret |= compare(rotated.Y(), 8.106555, "y diff", 1e10);
+ iret |= compare(rotated.Z(), -21.199782, "z diff", 1e10);
if (iret == 0) std::cout << "\tOK\n";
else std::cout << "\t FAILED\n";
diff --git a/math/physics/src/TRotation.cxx b/math/physics/src/TRotation.cxx
index cbe0a49e26bf4..61c7187948a38 100644
--- a/math/physics/src/TRotation.cxx
+++ b/math/physics/src/TRotation.cxx
@@ -185,6 +185,7 @@ TVector3 class:
#include "TRotation.h"
#include "TMath.h"
#include "TQuaternion.h"
+#include <cmath>
ClassImp(TRotation);
@@ -323,7 +324,7 @@ TRotation::TRotation(const TQuaternion & Q) {
/// Rotate along an axis.
TRotation & TRotation::Rotate(Double_t a, const TVector3& axis) {
- if (a != 0.0) {
+ if (std::fmod(a, 2 * TMath::Pi()) != 0.) {
Double_t ll = axis.Mag();
if (ll == 0.0) {
Warning("Rotate(angle,axis)"," zero axis");