getRotation() does not work as expected in python

[isorrentino]

The function getRotation() returns a reference but the python does not have the ownership. Let’s consider these lines of code that are part of a function.

H = self.kindyn.getWorldTransform(imu)
self.world_R_imu = H.getRotation()

the matrix H will not exist once out from the function and as a consequence, the global variable self.world_R_imu = H.getRotation() will contain garbage.

cc @GiulioRomualdi

[traversaro]

Can you provide a complete example (see https://stackoverflow.com/help/minimal-reproducible-example) that reproduces the problem? For example, it is not clear to me if:

H = self.kindyn.getWorldTransform(imu)
self.world_R_imu = iDynTree.Rotation()
self.world_R_imu = H.getRotation()

would have the same problem.

[isorrentino]

Here is an example. I don't know why, but in this case example, the problem is not occurring.

I highlighted the main differences with my code in the comments.

import numpy as np
import idyntree.bindings as idyn
from scipy.spatial.transform import Rotation


class Example:
    def __init__(self):
        self.R1 = idyn.Rotation()
        self.R2 = idyn.Rotation()

    def get_rotation(self):

        H = idyn.Transform()

        pos = idyn.Position().FromPython(np.ones(3))
        R1 = idyn.Rotation().FromPython(Rotation.random().as_matrix())

        H.setPosition(pos)
        H.setRotation(R1)

        self.R1 = H.getRotation()

        R2 = idyn.Rotation().FromPython(Rotation.random().as_matrix())
        H.setRotation(R2)
        self.R2 = H.getRotation()

        # In my case, H adn R are computed as
        # H = kindyn.getWorldTransform(frame1)
        # self.world_R_frame1[frame1] = H.getRotation()
        #
        # H = kindyn.getWorldTransform(frame2)
        # self.world_R_frame2[frame2] = H.getRotation()
        #
        # where kindyn is a iDynTree.KinDynComputations() object

        print("in getRotation:")
        print(self.R1.toNumPy())
        print(self.R2.toNumPy())

    def test_rotation(self):
        print("Test rotation:")
        print(self.R1.toNumPy())
        print(self.R2.toNumPy())


if __name__ == "__main__":

    test = Example()

    test.get_rotation()

    test.test_rotation()