Add CommonConversions and ManifConversions library

[prashanthr05]

This PR includes basic aliases and conversions between Eigen/manif/iDynTree.

This PR includes conversions between Eigen/manif/iDynTree objects.
Currently, only conversions of transform objects are included.

[S-Dafarra]

I think we have to pay attention to the definition of the Common library. This is most likely going to be a dependency for all the libraries inside the framework. Maybe it is worth separating the actual commonalities, from the conversion utilities.

What about creating a library, like Conversions, that inside links to a different library according to the specific library?

In this way, even if we depend on a new library, we can add conversion functions without the risk of making the new library a dependency for all the components. This is what we are doing already with yarp for example.

@traversaro @GiulioRomualdi what do you think?

[prashanthr05]

I think we have to pay attention to the definition of the Common library. This is most likely going to be a dependency for all the libraries inside the framework. Maybe it is worth separating the actual commonalities, from the conversion utilities.

What about creating a library, like Conversions, that inside links to a different library according to the specific library?

In this way, even if we depend on a new library, we can add conversion functions without the risk of making the new library a dependency for all the components. This is what we are doing already with yarp for example.

@traversaro @GiulioRomualdi what do you think?

Agreed. That would be a more scalable solution. Under the Conversions library, we might define different targets depending on the specific library we want to convert from. We might also define the associated aliases/typedefs with these targets.

[traversaro]

I think that conversions as separate library/libraries make sense. Furthermore, I am not sure it is good idea to have all those definitions, as I think they will complicate the readability of the API. For example, everyone knows what a Eigen::Matrix3d is, why defining a function as:

void functionThatTakesARotationMatrix(BipedalLocomotion::Common::Definitions::Rotation rot)

when I think it would be much more easy to read and use as:

void functionThatTakesARotationMatrix(Eigen::Matrix3d rot)

Also for conversions, I think that:

void Conversions::eigenRotTrans2ManifPose(Eigen::Ref<const Definitions::RotationMatrix> rotation,
                                          Eigen::Ref<const Definitions::Position> translation,
                                          Definitions::Pose& pose)

is not really clear, while:

void Conversions::eigenRotTrans2ManifPose(Eigen::Ref<const Eigen::Matrix3d> rotation,
                                          Eigen::Ref<const Eigen::Vector3d> translation,
                                          manif::SE3d& pose)

you get what this function is doing directly.

[prashanthr05]

I've made some relevant changes.

[GiulioRomualdi]

@prashanthr05, Thanks for iterating.
If @traversaro and @S-Dafarra agree we can proceed with the merge

[GiulioRomualdi]

@prashanthr05 last comment, could you update the CHANGELOG.md?

[prashanthr05]

@prashanthr05 last comment, could you update the CHANGELOG.md?

Done in 1c17dc6.

[S-Dafarra]

I noticed that the versions are somehow duplicate. Are the versions returning void needed?

[S-Dafarra]

I was thinking about the naming. Is it necessary to be so specific about the input types? We could just specify the output type, like toManifPose, then the input type is automatically deduced, similar to the toEigen of iDynTree.

[prashanthr05]

I was thinking about the naming. Is it necessary to be so specific about the input types? We could just specify the output type, like toManifPose, then the input type is automatically deduced, similar to the toEigen of iDynTree.

Thanks for this suggestion.

I have made the requested changes in b6eadd6

[GiulioRomualdi]

@prashanthr05 let me know if you want to reorganize the commits. Otherwise, I can merge

[prashanthr05]

@GiulioRomualdi I have reorganized the commits. You could proceed with the merge after the CI passes, thank you!

[GiulioRomualdi]

Merging! Thank you all!