"OBJ" mesh not following moved "GMSH" using "BarycentricMapping"

[CarlHenrikPreberEttesvoll]

Hi,

I have been playing around with SofaPyhton3, and i am now trying to use the 'TransformEngine' to move a 'TetrahedronSetTopologyContainer', and use a combination of 'OBJ' and 'GMSH' meshes with 'BarycentricMapping'.

I do it in the following way now:

ball.addObject('MeshOBJLoader', name="meshLoaderBall_obj", filename=f"mesh/{ball_mesh_name}/{ball_mesh_name}.obj")
ball.addObject('MeshGmshLoader', name="meshLoaderBall_msh", filename=f"mesh/{ball_mesh_name}/{ball_mesh_name}.msh")
ball.addObject('TransformEngine', name="MovedBall_msh", input_position="@meshLoaderBall_msh.position", translation=start_position_mm)

# ----------- Ball mechanics ------------- #
ball.addObject('EulerImplicitSolver')
ball.addObject('CGLinearSolver', iterations="200", tolerance="1e-9", threshold="1e-9")

ball.addObject('TetrahedronSetTopologyContainer', name="topo", src="@meshLoaderBall_msh")
ball.addObject('TetrahedronSetGeometryAlgorithms', template="Vec3d", name="GeomAlgo")

ball.addObject('MechanicalObject', template="Vec3d", name="MechanicalModelBall", position="@MovedBall_msh.output_position",
               showObject="1")
ball.addObject('TetrahedronFEMForceField', name="FEM", youngModulus=f"{ball_base_young_modulus/1e6}", poissonRatio="0.4")
ball.addObject('UniformMass', totalMass="0.002")

ball.addObject('PrecomputedConstraintCorrection')

# ----------- Visualization ------------- #
ball_visualisation = ball.addChild('VisualModel')
ball_visualisation.addObject('MeshTopology', src="@../meshLoaderBall_obj")
ball_visualisation.addObject('OglModel', name="VisualModel", color=[1.0, 0.0, 0.0, 1.0])
ball_visualisation.addObject('BarycentricMapping', name="VisualMapping", input="@../MechanicalModelBall", output="@VisualModel")

However doing it in this way does not move the "VisualModel" defined by the "OBJ" mesh on top of the mechanical object defined by the "GMSH" mesh. Result can be seen here:

At the same time if I change the mapping from "BarycentricMapping" to "IdentityMapping", I have no problem with moving the object, as can be seen here:

But as you can see, the visual model is not really that good when I do it this way, and I am also afraid the collision model will suffer aswell by doing it in this way (please correct me if I am wrong) . Additonally I think this is also incorrect use of the mapping according to my understanding of the following tutorial https://www.youtube.com/watch?v=GKH1lTvO_YM&t=12100s

I have tried the same on the example presented in tutorial around 4:01:22 with the liver, and here aswell it does not work as intended.

Does anybody have a clue what I might have done wrong here, and how to fix this?

Btw, great tool, however needs a bit more documentation! :)

[CarlHenrikPreberEttesvoll]

Hi,

I have fixed the problem by adding the same transform to both meshes and including the transform position into both the collision and visual model using the 'position' input when creating the two other obejcts.