[mapping] new component (BeamProjectionDifferenceMultiMapping)

[EulalieCoevoet]

This PR adds a new component with an example and test.

BeamProjectionDifferenceMultiMapping : This mapping takes some points and a beam as inputs, and outputs the difference between the points and their projection on the beam. The output difference is expressed in the local frame (wrt the beam), allowing the set up of constraints such as a fixing constraint (ex: attach a beam to another model) and sliding constraint (ex: constrain an object to slide on a beam).

Example of usage :
(you can also try the example examples/python3/component/BeamProjectionDifferenceMultiMapping.py)

# This will constrain a particle (a rigid frame) to slide along a beam
  sliding = particle.addChild('SlidingConstraint')
  beam.addChild(sliding)
  sliding.addObject('MechanicalObject', template='Rigid3', position=[0, 0, 0, 0, 0, 0, 0])  
  sliding.addObject('RestShapeSpringsForceField', stiffness=1e6)  # Put a spring on the difference to maintain it to zero
  sliding.addObject('BeamProjectionDifferenceMultiMapping',
                    directions=[0, 1, 1, 0, 0, 0, 0],  # The directions to compute
                    # Here only y, z positions to allow the particle to slide on the beam's principal direction, x
                    input1=particle.getMechanicalState().linkpath,  # The particle (a rigid frame)
                    indicesInput1=[0],  # Indices to use in the input1 model
                    input2=beam.getMechanicalState().linkpath,  # The beam on which to project the particle
                    interpolationInput2=beam.BeamInterpolation.linkpath,
                    output=sliding.getMechanicalState().linkpath  # This will contain the difference (in local frame) between the particle and its projection on the beam
                    )

The test has not been added to the project because it crashes. I didn't manage to debug it yet, although it was working not so long ago. I would still like to merge it to avoid losing it.

[epernod]

Could you describe a bit more when this component can be used?
If you have 2 points and a beam of 10 nodes. Does it project the 2 points on each node or only on the closest?

The points to be projected can only be in rigid?

[EulalieCoevoet]

When this component can be used?
Well, as I said if you want to attach a Rigid (can be another beam) to a beam, or if you want to constrain a Rigid to slide on a beam (only in position, only in rotation, or both in position and rotation). I show different usages in the example.

If you have 2 points and a beam of 10 nodes. Does it project the 2 points on each node or only on the closest?
It's the orthogonal projection of the points on the beam (can be none).

The points to be projected can only be in rigid?
I've only implemented the Rigid template yes.