Why is enabling CUDA for elastic objects look different?

[VikranthMallru]

In the video uploaded, the first simulation is without using SOFA-CUDA
The second is with SofaCuda but it shows different behaviour?
The material being used is the same, same youngs modulus and same poissons and also the same exact mesh.vtk file
I have 3d printed this using TPU, and it works like in the 1st sim(like 1st sim seems more accurate, without CUDA), so how can i make the CUDA one more accurate?
Screencast from 2025-06-28 17-04-41.webm

[alxbilger]

What did you change in your scene when switching to CUDA? Are there any warning or error messages in the console?

[VikranthMallru]

[WARNING] [SceneCheckDuplicatedName]   
- Found duplicated names ['Sofa.Component.Constraint.Lagrangian.Correction', ] in node '/'  
Nodes with similar names at the same level in your scene can crash certain operations, please rename them
[WARNING] [SceneCheckUsingAlias] This scene is using hard coded aliases. Aliases can be very confusing, use with caution.  
  - CollisionPipeline: 1 created with alias "DefaultPipeline" This alias will be REMOVED at the SOFA release v22.06, please update your scenes.
[INFO]    [SceneCheckerVisitor] Finished validating node "root".
[WARNING] [TetrahedronFEMForceField(forcefield)] buildDampingMatrix not implemented: for compatibility reason, the deprecated API (addBToMatrix) will be used. This compatibility will disapear in the future, and will cause issues in simulations. Please update the code of TetrahedronFEMForceField to ensure right behavior: the function addBToMatrix has been replaced by buildDampingMatrix

these were the warnings shown

I am using the ElasticMaterialObject() as a template from this link:

https://stlib.readthedocs.io/en/latest/_modules/stlib/physics/deformable/elasticmaterialobject.html

and make a cuda version like this

 import Sofa
 from stlib3.visuals import VisualModel

 class CudaElasticMaterialObject(Sofa.Prefab):


    prefabParameters = [
        {'name': 'volumeMeshFileName', 'type': 'string', 'help': 'Path to volume mesh file', 'default': ''},
        {'name': 'rotation', 'type': 'Vec3d', 'help': 'Rotation', 'default': [0.0, 0.0, 0.0]},
        {'name': 'translation', 'type': 'Vec3d', 'help': 'Translation', 'default': [0.0, 0.0, 0.0]},
        {'name': 'scale', 'type': 'Vec3d', 'help': 'Scale 3d', 'default': [1.0, 1.0, 1.0]},
        {'name': 'surfaceMeshFileName', 'type': 'string', 'help': 'Path to surface mesh file', 'default': ''},
        {'name': 'collisionMesh', 'type': 'string', 'help': 'Path to collision mesh file', 'default': ''},
        {'name': 'withConstrain', 'type': 'bool', 'help': 'Add constraint correction', 'default': True},
        {'name': 'surfaceColor', 'type': 'Vec4d', 'help': 'Color of surface mesh', 'default': [1., 1., 1., 1.]},
        {'name': 'poissonRatio', 'type': 'double', 'help': 'Poisson ratio', 'default': 0.3},
        {'name': 'youngModulus', 'type': 'double', 'help': "Young's modulus", 'default': 18000},
        {'name': 'totalMass', 'type': 'double', 'help': 'Total mass', 'default': 1.0},
        {'name': 'solverName', 'type': 'string', 'help': 'Solver name', 'default': ''},
        {'name': 'fixedIndices', 'type': 'string', 'help': 'Indices of fixed nodes, space separated', 'default': ''},
    ]

    def __init__(self, *args, **kwargs):
        Sofa.Prefab.__init__(self, *args, **kwargs)

    def init(self):
        # Load required plugins
        self.addObject('RequiredPlugin', name="SofaCUDA")
        self.addObject('RequiredPlugin', name="Sofa.Component.Topology.Container.Dynamic")

        # Solver setup: EulerImplicitSolver + CGLinearSolver (CUDA compatible, assembled matrix)
        if self.solverName.value == '':
            self.integration = self.addObject(
                'EulerImplicitSolver',
                name='integration',
                rayleighStiffness=0.1,
                rayleighMass=0.1
            )
            self.solver = self.addObject(
            'CGLinearSolver',
            name="solver",
            template='CompressedRowSparseMatrixMat3x3d',
            iterations=100,
            tolerance=1e-8,  # More strict
            threshold=1e-20
        )

        # Mesh loading
        if self.volumeMeshFileName.value == '':
            Sofa.msg_error(self, "Unable to create an elastic object because there is no volume mesh provided.")
            return None

        mesh_kwargs = dict(
            name='loader',
            filename=self.volumeMeshFileName.value,
            rotation=list(self.rotation.value),
            translation=list(self.translation.value),
            scale3d=list(self.scale.value)
        )

        if self.volumeMeshFileName.value.endswith(".msh"):
            self.loader = self.addObject('MeshGmshLoader', **mesh_kwargs)
        elif self.volumeMeshFileName.value.endswith(".gidmsh"):
            self.loader = self.addObject('GIDMeshLoader', **mesh_kwargs)
        else:
            self.loader = self.addObject('MeshVTKLoader', **mesh_kwargs)

        # Topology and mechanics
        self.container = self.addObject(
            'TetrahedronSetTopologyContainer',
            position=self.loader.position.getLinkPath(),
            tetras=self.loader.tetras.getLinkPath(),
            name='container'
        )
        self.dofs = self.addObject('MechanicalObject', template='CudaVec3f', name='dofs')
        self.geometry = self.addObject('TetrahedronSetGeometryAlgorithms', template='CudaVec3f', name='GeomAlgo')

        self.mass = self.addObject(
            'UniformMass',
            totalMass=self.totalMass.value,
            name='UniformMass'
        )


        # FEM forcefield with CUDA and matrix-free (computeGlobalMatrix=False)
        self.forcefield = self.addObject(
            'TetrahedronFEMForceField',
            template='CudaVec3f',
            method='large',
            name='forcefield',
            poissonRatio=self.poissonRatio.value,
            youngModulus=self.youngModulus.value,
            computeGlobalMatrix=False
        )

        # Fixed constraint: fix nodes if indices are given
        if self.fixedIndices.value.strip():
            self.fixedConstraint = self.addObject(
                'FixedConstraint',
                template='CudaVec3f',
                topology='@container',
                indices=self.fixedIndices.value
            )

        # Optional: Add constraint correction if requested (not needed if using FixedConstraint)
        if self.withConstrain.value and not self.fixedIndices.value.strip():
            self.correction = self.addObject('LinearSolverConstraintCorrection', name='correction')

        # Collision model (mesh-based)
        if self.collisionMesh:
            self.addCollisionModel(
                self.collisionMesh.value,
                list(self.rotation.value),
                list(self.translation.value),
                list(self.scale.value)
            )

        # Visual model
        if self.surfaceMeshFileName:
            self.addVisualModel(
                self.surfaceMeshFileName.value,
                list(self.surfaceColor.value),
                list(self.rotation.value),
                list(self.translation.value),
                list(self.scale.value)
            )

    def addCollisionModel(self, collisionMesh, rotation=[0.0, 0.0, 0.0], translation=[0.0, 0.0, 0.0], scale=[1., 1., 1.]):
        self.collisionmodel = self.addChild('CollisionModel')
        self.collisionmodel.addObject(
            'MeshSTLLoader',
            name='loader',
            filename=collisionMesh,
            rotation=rotation,
            translation=translation,
            scale3d=scale
        )
        self.collisionmodel.addObject('TriangleSetTopologyContainer', src='@loader', name='container')
        self.collisionmodel.addObject('MechanicalObject', template='Vec3', name='dofs')
        self.collisionmodel.addObject('TriangleCollisionModel')
        self.collisionmodel.addObject('LineCollisionModel')
        self.collisionmodel.addObject('PointCollisionModel')
        self.collisionmodel.addObject('BarycentricMapping')

        # self.collisionmodel.TriangleCollisionModel.selfCollision = True
        # self.collisionmodel.LineCollisionModel.selfCollision = True
        # self.collisionmodel.PointCollisionModel.selfCollision = True

    def addVisualModel(self, filename, color, rotation, translation, scale=[1., 1., 1.]):
        visualmodel = self.addChild(VisualModel(
            visualMeshPath=filename,
            color=color,
            rotation=rotation,
            translation=translation,
            scale=scale
        ))
        visualmodel.addObject('BarycentricMapping', name='mapping')

No other changes to the object were made

Here is a video adding to it for more clarity:
Screencast from 2025-06-30 17-32-18.webm

[VikranthMallru]

Hello! @alxbilger
I have been hitting this roadblock and I'm unaware how I can proceed, can you please help?
Thank you so much