sofa-framework · alxbilger · Sep 3, 2026 · Sep 3, 2026
diff --git a/Sofa/Component/LinearSystem/tests/MatrixLinearSystem_test.cpp b/Sofa/Component/LinearSystem/tests/MatrixLinearSystem_test.cpp
@@ -137,7 +137,7 @@ TEST(LinearSystem, MatrixSystem_springForceField)
     // Compute the external force. This step is mandatory because most of the time force fields
     // pre-computes required elements for the matrix assembly in the addForce method
     sofa::core::MultiVecDerivId ffId = sofa::core::vec_id::write_access::externalForce;
-    ((sofa::core::behavior::BaseForceField*)spring.get())->addForce(&mparams, ffId);
+    ((sofa::core::behavior::BaseForceField*)spring.get())->addForce(&mparams, ffId, mparams.x(), mparams.v());
 
 
     // Finally build the system matrix, which is composed of only the stiffness matrix from the spring force field

diff --git a/Sofa/framework/Core/src/sofa/core/behavior/BaseForceField.cpp b/Sofa/framework/Core/src/sofa/core/behavior/BaseForceField.cpp
@@ -35,6 +35,12 @@ BaseForceField::BaseForceField()
 {
 }
 
+void BaseForceField::addForce(const MechanicalParams* mparams, MultiVecDerivId fId)
+{
+    assert(mparams);
+    addForce(mparams, fId, mparams->x(), mparams->v());
+}
+
 void BaseForceField::addMBKdx(const MechanicalParams* mparams, MultiVecDerivId dfId)
 {
     const auto kFactor = sofa::core::mechanicalparams::kFactorIncludingRayleighDamping(mparams,rayleighStiffness.getValue());

diff --git a/Sofa/framework/Core/src/sofa/core/behavior/BaseForceField.h b/Sofa/framework/Core/src/sofa/core/behavior/BaseForceField.h
@@ -79,13 +79,15 @@ class SOFA_CORE_API BaseForceField : public virtual StateAccessor
     /// \param mparams
     /// - \a sofa::core::mechanicalparams::bFactor(mparams) is the coefficient for damping contributions (i.e. first derivatives term in the ODE)
     /// - \a mparams->kFactor() is the coefficient for stiffness contributions (i.e. DOFs term in the ODE)
-    /// - \a mparams->readX() is the input vector of position
-    /// - \a mparams->readV() is the input vector of velocity
-    /// - \a mparams->readF() is the input vector of force
     /// - if \a mparams->energy() is true, the method computes and internally stores the potential energy,
     /// which will be subsequently returned by method getPotentialEnergy()
     /// \param fId the output vector of forces
-    virtual void addForce(const MechanicalParams* mparams, MultiVecDerivId fId )=0;
+    /// \param xId the input vector for positions
+    /// \param vId the input vector for velocities
+    virtual void addForce(const MechanicalParams* mparams, MultiVecDerivId fId,
+        ConstMultiVecCoordId xId, ConstMultiVecDerivId vId )=0;
+    SOFA_ATTRIBUTE_DEPRECATED__ADDFORCE_OVERLOAD()
+    virtual void addForce(const MechanicalParams* mparams, MultiVecDerivId fId ) final;
 
     /// \brief Compute the force derivative given a small displacement from the
     /// position and velocity used in the previous call to addForce().

diff --git a/Sofa/framework/Core/src/sofa/core/behavior/ForceField.h b/Sofa/framework/Core/src/sofa/core/behavior/ForceField.h
@@ -74,7 +74,7 @@ class ForceField : public BaseForceField, public virtual SingleStateAccessor<TDa
     /// This method retrieves the force, x and v vector from the MechanicalState
     /// and call the internal addForce(const MechanicalParams*, DataVecDeriv&,const DataVecCoord&,const DataVecDeriv&)
     /// method implemented by the component.
-    void addForce(const MechanicalParams* mparams, MultiVecDerivId fId ) override;
+    void addForce(const MechanicalParams* mparams, MultiVecDerivId fId, ConstMultiVecCoordId xId, ConstMultiVecDerivId vId ) override;
 
     /// Given the current position and velocity states, update the current force
     /// vector by computing and adding the forces associated with this

diff --git a/Sofa/framework/Core/src/sofa/core/behavior/ForceField.inl b/Sofa/framework/Core/src/sofa/core/behavior/ForceField.inl
@@ -41,12 +41,15 @@ template<class DataTypes>
 ForceField<DataTypes>::~ForceField() = default;
 
 template<class DataTypes>
-void ForceField<DataTypes>::addForce(const MechanicalParams* mparams, MultiVecDerivId fId )
+void ForceField<DataTypes>::addForce(const MechanicalParams* mparams, MultiVecDerivId fId,
+    ConstMultiVecCoordId xId, ConstMultiVecDerivId vId )
 {
-    auto mstate = this->mstate.get();
-    if (mparams && mstate)
+    if (mparams && this->mstate)
     {
-        addForce(mparams, *fId[mstate].write() , *mparams->readX(mstate), *mparams->readV(mstate));
+        DataVecDeriv* f = fId[this->mstate.get()].write(); assert(f);
+        const DataVecCoord* x = xId[this->mstate.get()].read(); assert(x);
+        const DataVecDeriv* v = vId[this->mstate.get()].read(); assert(v);
+        addForce(mparams, *f , *x, *v);
     }
 }
 

diff --git a/Sofa/framework/Core/src/sofa/core/behavior/MixedInteractionForceField.h b/Sofa/framework/Core/src/sofa/core/behavior/MixedInteractionForceField.h
@@ -80,7 +80,7 @@ class MixedInteractionForceField : public BaseInteractionForceField, public Pair
     /// This method retrieves the force, x and v vector from the two MechanicalState
     /// and call the internal addForce(VecDeriv&,VecDeriv&,const VecCoord&,const VecCoord&,const VecDeriv&,const VecDeriv&)
     /// method implemented by the component.
-    void addForce(const MechanicalParams* mparams, MultiVecDerivId fId ) override;
+    void addForce(const MechanicalParams* mparams, MultiVecDerivId fId, ConstMultiVecCoordId xId, ConstMultiVecDerivId vId ) override;
 
     /// Compute the force derivative given a small displacement from the
     /// position and velocity used in the previous call to addForce().

diff --git a/Sofa/framework/Core/src/sofa/core/behavior/MixedInteractionForceField.inl b/Sofa/framework/Core/src/sofa/core/behavior/MixedInteractionForceField.inl
@@ -43,17 +43,19 @@ MixedInteractionForceField<DataTypes1, DataTypes2>::~MixedInteractionForceField(
 }
 
 template<class DataTypes1, class DataTypes2>
-void MixedInteractionForceField<DataTypes1, DataTypes2>::addForce(const MechanicalParams* mparams, MultiVecDerivId fId )
+void MixedInteractionForceField<DataTypes1, DataTypes2>::addForce(
+    const MechanicalParams* mparams, MultiVecDerivId fId, ConstMultiVecCoordId xId, ConstMultiVecDerivId vId )
 {
-
     if (this->mstate1 && this->mstate2)
     {
-        auto state1 = this->mstate1.get();
-        auto state2 = this->mstate2.get();
-        addForce( mparams, *fId[state1].write(), *fId[state2].write(),
-                  *mparams->readX(state1), *mparams->readX(state2),
-                  *mparams->readV(state1), *mparams->readV(state2));
-
+        DataVecDeriv1* f1 = fId[this->mstate1.get()].write(); assert(f1);
+        DataVecDeriv2* f2 = fId[this->mstate2.get()].write(); assert(f2);
+        const DataVecCoord1* x1 = xId[this->mstate1.get()].read(); assert(x1);
+        const DataVecDeriv1* v1 = vId[this->mstate1.get()].read(); assert(v1);
+        const DataVecCoord2* x2 = xId[this->mstate2.get()].read(); assert(x2);
+        const DataVecDeriv2* v2 = vId[this->mstate2.get()].read(); assert(v2);
+
+        addForce(mparams, *f1, *f2, *x1, *x2, *v1, *v2);
     }
 }
 

diff --git a/Sofa/framework/Core/src/sofa/core/behavior/PairInteractionForceField.h b/Sofa/framework/Core/src/sofa/core/behavior/PairInteractionForceField.h
@@ -80,7 +80,7 @@ class PairInteractionForceField : public BaseInteractionForceField, public PairS
     /// This method retrieves the force, x and v vector from the two MechanicalState
     /// and call the internal addForce(VecDeriv&,VecDeriv&,const VecCoord&,const VecCoord&,const VecDeriv&,const VecDeriv&)
     /// method implemented by the component.
-    void addForce(const MechanicalParams* mparams, MultiVecDerivId fId ) override;
+    void addForce(const MechanicalParams* mparams, MultiVecDerivId fId, ConstMultiVecCoordId xId, ConstMultiVecDerivId vId) override;
 
     /// Given the current position and velocity states, update the current force
     /// vector by computing and adding the forces associated with this

diff --git a/Sofa/framework/Core/src/sofa/core/behavior/PairInteractionForceField.inl b/Sofa/framework/Core/src/sofa/core/behavior/PairInteractionForceField.inl
@@ -46,15 +46,20 @@ PairInteractionForceField<DataTypes>::~PairInteractionForceField()
 }
 
 template<class DataTypes>
-void PairInteractionForceField<DataTypes>::addForce(const MechanicalParams* mparams, MultiVecDerivId fId )
+void PairInteractionForceField<DataTypes>::addForce(const MechanicalParams* mparams, MultiVecDerivId fId, ConstMultiVecCoordId xId, ConstMultiVecDerivId vId )
 {
     auto state1 = this->mstate1.get();
     auto state2 = this->mstate2.get();
     if (state1 && state2)
     {
-        addForce(mparams, *fId[state1].write(), *fId[state2].write(),
-            *mparams->readX(state1), *mparams->readX(state2),
-            *mparams->readV(state1), *mparams->readV(state2));
+        DataVecDeriv* f1 = fId[this->mstate1.get()].write(); assert(f1);
+        DataVecDeriv* f2 = fId[this->mstate2.get()].write(); assert(f2);
+        const DataVecCoord* x1 = xId[this->mstate1.get()].read(); assert(x1);
+        const DataVecDeriv* v1 = vId[this->mstate1.get()].read(); assert(v1);
+        const DataVecCoord* x2 = xId[this->mstate2.get()].read(); assert(x2);
+        const DataVecDeriv* v2 = vId[this->mstate2.get()].read(); assert(v2);
+
+        addForce(mparams, *f1, *f2, *x1, *x2, *v1, *v2);
     }
     else
         msg_error() << "PairInteractionForceField<DataTypes>::addForce(const MechanicalParams* /*mparams*/, MultiVecDerivId /*fId*/ ), mstate missing";

diff --git a/Sofa/framework/Core/src/sofa/core/config.h.in b/Sofa/framework/Core/src/sofa/core/config.h.in
@@ -127,3 +127,10 @@ SOFA_ATTRIBUTE_DEPRECATED("v26.06", "v29.06", "Use toBaseComponent instead.")
 #define SOFA_CORE_DEPRECATED_RENAME_CREATORMAP_OBJECTTEMPLATECREATORMAP() \
     SOFA_ATTRIBUTE_DISABLED("v25.12", "v26.06", "Type CreatorMap has been renamed to ObjectTemplateCreatorMap.")
 #endif
+
+#ifdef SOFA_BUILD_SOFA_CORE
+#define SOFA_ATTRIBUTE_DEPRECATED__ADDFORCE_OVERLOAD()
+#else
+#define SOFA_ATTRIBUTE_DEPRECATED__ADDFORCE_OVERLOAD() \
+    SOFA_ATTRIBUTE_DEPRECATED("v26.12", "v27.06", "addForce must be called by providing the position vector.")
+#endif
diff --git a/Sofa/framework/Simulation/Core/src/sofa/simulation/MappingGraphMechanicalOperations.cpp b/Sofa/framework/Simulation/Core/src/sofa/simulation/MappingGraphMechanicalOperations.cpp
@@ -40,6 +40,8 @@ void MappingGraphMechanicalOperations::projectResponse(const MappingGraph& mappi
 
 void MappingGraphMechanicalOperations::computeForce(const MappingGraph& mappingGraph,
                                                     core::MultiVecDerivId result,
+                                                    core::ConstMultiVecCoordId xId,
+                                                    core::ConstMultiVecDerivId vId,
                                                     bool clearForceBefore,
                                                     bool accumulateForcesFromMappedStates,
                                                     TaskScheduler* taskScheduler)
@@ -76,7 +78,7 @@ void MappingGraphMechanicalOperations::computeForce(const MappingGraph& mappingG
      */
     mappingGraph.algorithms.traverseComponentGroups_([&](core::behavior::BaseForceField& forceField)
     {
-        forceField.addForce(&mparams, result);
+        forceField.addForce(&mparams, result, xId, vId);
     }, sofa::simulation::VisitorApplication::ALL_NODES, taskScheduler);
 
     if (accumulateForcesFromMappedStates)
@@ -91,6 +93,16 @@ void MappingGraphMechanicalOperations::computeForce(const MappingGraph& mappingG
         });
     }
 }
+
+void MappingGraphMechanicalOperations::computeForce(const MappingGraph& mappingGraph,
+                                                    core::MultiVecDerivId result,
+                                                    bool clearForceBefore,
+                                                    bool accumulateForcesFromMappedStates,
+                                                    TaskScheduler* taskScheduler)
+{
+    computeForce(mappingGraph, result, mparams.x(), mparams.v(), clearForceBefore, accumulateForcesFromMappedStates, taskScheduler);
+}
+
 void MappingGraphMechanicalOperations::addMBKv(const MappingGraph& mappingGraph,
                                                core::MultiVecDerivId df, core::MatricesFactors::M m,
                                                core::MatricesFactors::B b,

diff --git a/Sofa/framework/Simulation/Core/src/sofa/simulation/MappingGraphMechanicalOperations.h b/Sofa/framework/Simulation/Core/src/sofa/simulation/MappingGraphMechanicalOperations.h
@@ -53,6 +53,10 @@ class SOFA_SIMULATION_CORE_API MappingGraphMechanicalOperations : public Mechani
     using MechanicalOperations::projectResponse;
 
     /// Compute the current force (given the latest propagated position and velocity)
+    void computeForce(const MappingGraph& mappingGraph, core::MultiVecDerivId result,
+        core::ConstMultiVecCoordId xId, core::ConstMultiVecDerivId vId,
+        bool clearForceBefore, bool accumulateForcesFromMappedStates, TaskScheduler* taskScheduler);
+    SOFA_ATTRIBUTE_DEPRECATED__COMPUTEFORCE_OVERLOAD()
     void computeForce(const MappingGraph& mappingGraph, core::MultiVecDerivId result, bool clearForceBefore, bool accumulateForcesFromMappedStates, TaskScheduler* taskScheduler);
     using MechanicalOperations::computeForce;
 

diff --git a/Sofa/framework/Simulation/Core/src/sofa/simulation/MechanicalOperations.cpp b/Sofa/framework/Simulation/Core/src/sofa/simulation/MechanicalOperations.cpp
@@ -204,6 +204,7 @@ void MechanicalOperations::computeEnergy(SReal &kineticEnergy, SReal &potentialE
     kineticEnergy = energyVisitor.getKineticEnergy();
     potentialEnergy = energyVisitor.getPotentialEnergy();
 }
+
 /// Apply projective constraints to the given velocity vector
 void MechanicalOperations::projectVelocity(core::MultiVecDerivId v, SReal time)
 {
@@ -248,15 +249,22 @@ void MechanicalOperations::accFromF(core::MultiVecDerivId a, core::ConstMultiVec
 }
 
 /// Compute the current force (given the latest propagated position and velocity)
-void MechanicalOperations::computeForce(core::MultiVecDerivId result, bool clear, bool accumulate)
+void MechanicalOperations::computeForce(core::MultiVecDerivId result,
+                                        core::ConstMultiVecCoordId xId,
+                                        core::ConstMultiVecDerivId vId, bool clear, bool accumulate)
 {
     setF(result);
     if (clear)
     {
         executeVisitor( MechanicalResetForceVisitor(&mparams, result, false) );
         //finish();
     }
-    executeVisitor( MechanicalComputeForceVisitor(&mparams, result, accumulate) );
+    executeVisitor( MechanicalComputeForceVisitor(&mparams, result, xId, vId, accumulate) );
+}
+
+void MechanicalOperations::computeForce(core::MultiVecDerivId result, bool clear, bool accumulate)
+{
+    computeForce(result, mparams.x(), mparams.v(), clear, accumulate);
 }
 
 

diff --git a/Sofa/framework/Simulation/Core/src/sofa/simulation/MechanicalOperations.h b/Sofa/framework/Simulation/Core/src/sofa/simulation/MechanicalOperations.h
@@ -77,6 +77,9 @@ class SOFA_SIMULATION_CORE_API MechanicalOperations
     /// Compute Energy
     void computeEnergy(SReal &kineticEnergy, SReal &potentialEnergy);
     /// Compute the current force (given the latest propagated position and velocity)
+    void computeForce(core::MultiVecDerivId result, core::ConstMultiVecCoordId xId, core::ConstMultiVecDerivId vId,
+        bool clear = true, bool accumulate = true);
+    SOFA_ATTRIBUTE_DEPRECATED__COMPUTEFORCE_OVERLOAD()
     void computeForce(core::MultiVecDerivId result, bool clear = true, bool accumulate = true);
     /// Compute the current force delta (given the latest propagated displacement)
     void computeDf(core::MultiVecDerivId df, bool clear = true, bool accumulate = true);

diff --git a/Sofa/framework/Simulation/Core/src/sofa/simulation/SolveVisitor.cpp b/Sofa/framework/Simulation/Core/src/sofa/simulation/SolveVisitor.cpp
@@ -45,7 +45,7 @@ void SolveVisitor::fwdInteractionForceField(Node* node, core::behavior::BaseInte
     const core::MultiVecDerivId ffId = core::vec_id::write_access::externalForce;
     core::MechanicalParams mparams;
     mparams.setDt(dt);
-    forceField->addForce(&mparams, ffId);
+    forceField->addForce(&mparams, ffId, mparams.x(), mparams.v());
 }
 
 Visitor::Result SolveVisitor::processNodeTopDown(simulation::Node* node)

diff --git a/Sofa/framework/Simulation/Core/src/sofa/simulation/config.h.in b/Sofa/framework/Simulation/Core/src/sofa/simulation/config.h.in
@@ -38,3 +38,17 @@
 #define SOFA_ATTRIBUTE_DEPRECATED__MECHANICALGETNONDIAGONALMASSESCOUNTIVISITOR() \
     SOFA_ATTRIBUTE_DISABLED("v26.12", "v27.06", "This visitor is unused.")
 #endif
+
+#ifdef SOFA_BUILD_SOFA_SIMULATION_CORE
+#define SOFA_ATTRIBUTE_DEPRECATED__MECHANICALCOMPUTEFORCEVISITOR_CONSTRUCTOR_OVERLOAD()
+#else
+#define SOFA_ATTRIBUTE_DEPRECATED__MECHANICALCOMPUTEFORCEVISITOR_CONSTRUCTOR_OVERLOAD() \
+    SOFA_ATTRIBUTE_DISABLED("v26.12", "v27.06", "Constructor must be used by providing the x and v vectors.")
+#endif
+
+#ifdef SOFA_BUILD_SOFA_SIMULATION_CORE
+#define SOFA_ATTRIBUTE_DEPRECATED__COMPUTEFORCE_OVERLOAD()
+#else
+#define SOFA_ATTRIBUTE_DEPRECATED__COMPUTEFORCE_OVERLOAD() \
+    SOFA_ATTRIBUTE_DISABLED("v26.12", "v27.06", "computeForce must be used by providing the x and v vectors.")
+#endif
diff --git a/...k/Simulation/Core/src/sofa/simulation/mechanicalvisitor/MechanicalComputeForceVisitor.cpp b/...k/Simulation/Core/src/sofa/simulation/mechanicalvisitor/MechanicalComputeForceVisitor.cpp
@@ -43,7 +43,7 @@ Visitor::Result MechanicalComputeForceVisitor::fwdMappedMechanicalState(simulati
 
 Visitor::Result MechanicalComputeForceVisitor::fwdForceField(simulation::Node* /*node*/, core::behavior::BaseForceField* ff)
 {
-    ff->addForce(this->mparams, res);
+    ff->addForce(this->mparams, res, m_xId, m_vId);
 
     return RESULT_CONTINUE;
 }

diff --git a/...ork/Simulation/Core/src/sofa/simulation/mechanicalvisitor/MechanicalComputeForceVisitor.h b/...ork/Simulation/Core/src/sofa/simulation/mechanicalvisitor/MechanicalComputeForceVisitor.h
@@ -31,18 +31,33 @@ This action is typically called after a MechanicalResetForceVisitor.
 */
 class SOFA_SIMULATION_CORE_API MechanicalComputeForceVisitor : public MechanicalVisitor
 {
+    sofa::core::ConstMultiVecCoordId m_xId;
+    sofa::core::ConstMultiVecDerivId m_vId;
+
 public:
     sofa::core::MultiVecDerivId res;
     bool accumulate; ///< Accumulate everything back to the DOFs through the mappings
 
     MechanicalComputeForceVisitor(const sofa::core::MechanicalParams* mechaparams,
-                                  sofa::core::MultiVecDerivId resvecid, bool bAccumulate = true )
-            : MechanicalVisitor(mechaparams) , res(resvecid), accumulate(bAccumulate)
+                          sofa::core::MultiVecDerivId resvecid,
+                          sofa::core::ConstMultiVecCoordId xId,
+                          sofa::core::ConstMultiVecDerivId vId,
+                          bool bAccumulate = true )
+        : MechanicalVisitor(mechaparams),
+        m_xId(xId), m_vId(vId),
+        res(resvecid), accumulate(bAccumulate)
     {
 #ifdef SOFA_DUMP_VISITOR_INFO
         setReadWriteVectors();
 #endif
     }
+
+    SOFA_ATTRIBUTE_DEPRECATED__MECHANICALCOMPUTEFORCEVISITOR_CONSTRUCTOR_OVERLOAD()
+    MechanicalComputeForceVisitor(const sofa::core::MechanicalParams* mechaparams,
+                                  sofa::core::MultiVecDerivId resvecid, bool bAccumulate = true )
+        : MechanicalComputeForceVisitor(mechaparams, resvecid, mparams->x(), mparams->v(), bAccumulate)
+    {}
+
     Result fwdMechanicalState(simulation::Node* /*node*/,sofa::core::behavior::BaseMechanicalState* mm) override;
     Result fwdMappedMechanicalState(simulation::Node* /*node*/,sofa::core::behavior::BaseMechanicalState* mm) override;
     Result fwdForceField(simulation::Node* /*node*/,sofa::core::behavior::BaseForceField* ff) override;

diff --git a/...rk/Simulation/Core/src/sofa/simulation/mechanicalvisitor/MechanicalIntegrationVisitor.cpp b/...rk/Simulation/Core/src/sofa/simulation/mechanicalvisitor/MechanicalIntegrationVisitor.cpp
@@ -77,7 +77,7 @@ Visitor::Result MechanicalIntegrationVisitor::fwdInteractionForceField(simulatio
     core::MechanicalParams m_mparams(*this->params);
     m_mparams.setDt(this->dt);
 
-    obj->addForce(&m_mparams, ffId);
+    obj->addForce(&m_mparams, ffId, m_mparams.x(), m_mparams.v());
     return RESULT_CONTINUE;
 }
 

diff --git a/Sofa/framework/Simulation/Core/test/Visitor_test.cpp b/Sofa/framework/Simulation/Core/test/Visitor_test.cpp
@@ -88,7 +88,7 @@ class TestVisitorWithInteractionForceField : public simulation::MechanicalVisito
 class TestForceField : public core::behavior::BaseForceField
 {
 public:
-    void addForce(const core::MechanicalParams* mparams, core::MultiVecDerivId fId) override {}
+    void addForce(const core::MechanicalParams* mparams, core::MultiVecDerivId fId, core::ConstMultiVecCoordId xId, core::ConstMultiVecDerivId vId) override {}
     void addDForce(const core::MechanicalParams* mparams, core::MultiVecDerivId dfId) override {}
     SReal getPotentialEnergy(const core::MechanicalParams* mparams) const override { return {}; }
     void addKToMatrix(const core::MechanicalParams* mparams, const sofa::core::behavior::MultiMatrixAccessor* matrix) override {}
@@ -114,7 +114,7 @@ class TestMass : public core::behavior::BaseMass
 class TestInteractionForceField : public core::behavior::BaseInteractionForceField
 {
 public:
-    void addForce(const core::MechanicalParams* mparams, core::MultiVecDerivId fId) override {}
+    void addForce(const core::MechanicalParams* mparams, core::MultiVecDerivId fId, core::ConstMultiVecCoordId xId, core::ConstMultiVecDerivId vId) override {}
     void addDForce(const core::MechanicalParams* mparams, core::MultiVecDerivId dfId) override {}
     SReal getPotentialEnergy(const core::MechanicalParams* mparams) const override { return {}; }
 };