From e9ad9b2041d66165ac5c4f19b09a896960deec23 Mon Sep 17 00:00:00 2001
From: Alex Bilger <alexbilger0@gmail.com>
Date: Thu, 7 May 2026 12:47:20 +0200
Subject: [PATCH 1/2] [Mass] Support prisms in mass

---
 Sofa/Component/Mass/src/sofa/component/mass/ElementFEMMass.cpp | 3 +++
 Sofa/Component/Mass/src/sofa/component/mass/ElementFEMMass.h   | 1 +
 2 files changed, 4 insertions(+)

diff --git a/Sofa/Component/Mass/src/sofa/component/mass/ElementFEMMass.cpp b/Sofa/Component/Mass/src/sofa/component/mass/ElementFEMMass.cpp
index 7f4a5825806..e2c0f520e30 100644
--- a/Sofa/Component/Mass/src/sofa/component/mass/ElementFEMMass.cpp
+++ b/Sofa/Component/Mass/src/sofa/component/mass/ElementFEMMass.cpp
@@ -37,6 +37,7 @@ template class SOFA_COMPONENT_MASS_API ElementFEMMass<sofa::defaulttype::Vec2Typ
 template class SOFA_COMPONENT_MASS_API ElementFEMMass<sofa::defaulttype::Vec3Types, sofa::geometry::Quad>;
 template class SOFA_COMPONENT_MASS_API ElementFEMMass<sofa::defaulttype::Vec3Types, sofa::geometry::Tetrahedron>;
 template class SOFA_COMPONENT_MASS_API ElementFEMMass<sofa::defaulttype::Vec3Types, sofa::geometry::Hexahedron>;
+template class SOFA_COMPONENT_MASS_API ElementFEMMass<sofa::defaulttype::Vec3Types, sofa::geometry::Prism>;
 
 void registerFEMMass(sofa::core::ObjectFactory* factory)
 {
@@ -59,6 +60,8 @@ void registerFEMMass(sofa::core::ObjectFactory* factory)
     factory->registerObjects(sofa::core::ObjectRegistrationData("Finite-element mass (inertia and body force) defined on hexahedra")
         .add< ElementFEMMass<sofa::defaulttype::Vec3Types, sofa::geometry::Hexahedron> >(true));
 
+    factory->registerObjects(sofa::core::ObjectRegistrationData("Finite-element mass (inertia and body force) defined on prisms")
+        .add< ElementFEMMass<sofa::defaulttype::Vec3Types, sofa::geometry::Prism> >(true));
 }
 
 }
diff --git a/Sofa/Component/Mass/src/sofa/component/mass/ElementFEMMass.h b/Sofa/Component/Mass/src/sofa/component/mass/ElementFEMMass.h
index 61c1f9d820b..f390189c375 100644
--- a/Sofa/Component/Mass/src/sofa/component/mass/ElementFEMMass.h
+++ b/Sofa/Component/Mass/src/sofa/component/mass/ElementFEMMass.h
@@ -277,6 +277,7 @@ template class SOFA_COMPONENT_MASS_API ElementFEMMass<sofa::defaulttype::Vec2Typ
 template class SOFA_COMPONENT_MASS_API ElementFEMMass<sofa::defaulttype::Vec3Types, sofa::geometry::Quad>;
 template class SOFA_COMPONENT_MASS_API ElementFEMMass<sofa::defaulttype::Vec3Types, sofa::geometry::Tetrahedron>;
 template class SOFA_COMPONENT_MASS_API ElementFEMMass<sofa::defaulttype::Vec3Types, sofa::geometry::Hexahedron>;
+template class SOFA_COMPONENT_MASS_API ElementFEMMass<sofa::defaulttype::Vec3Types, sofa::geometry::Prism>;
 #endif
 
 }  // namespace sofa::component::mass

From 9d9c1adc0acd69879b79bd5c88e14519a19261ac Mon Sep 17 00:00:00 2001
From: Alex Bilger <alexbilger0@gmail.com>
Date: Thu, 7 May 2026 12:47:40 +0200
Subject: [PATCH 2/2] Adapt example to use mass with prisms

---
 .../Mapping/Hexa2PrismTopologicalMapping.scn      | 15 +++++++++------
 1 file changed, 9 insertions(+), 6 deletions(-)

diff --git a/examples/Component/Topology/Mapping/Hexa2PrismTopologicalMapping.scn b/examples/Component/Topology/Mapping/Hexa2PrismTopologicalMapping.scn
index e3c505eb7b6..c2867de54c2 100644
--- a/examples/Component/Topology/Mapping/Hexa2PrismTopologicalMapping.scn
+++ b/examples/Component/Topology/Mapping/Hexa2PrismTopologicalMapping.scn
@@ -5,13 +5,15 @@
         <RequiredPlugin pluginName="Sofa.Component.Constraint.Projective"/> <!-- Needed to use components [FixedProjectiveConstraint] -->
         <RequiredPlugin pluginName="Sofa.Component.Engine.Select"/> <!-- Needed to use components [BoxROI] -->
         <RequiredPlugin pluginName="Sofa.Component.LinearSolver.Direct"/> <!-- Needed to use components [SparseLDLSolver] -->
-        <RequiredPlugin pluginName="Sofa.Component.Mass"/> <!-- Needed to use components [MeshMatrixMass] -->
-        <RequiredPlugin pluginName="Sofa.Component.SolidMechanics.FEM.Elastic"/>
+        <RequiredPlugin pluginName="Sofa.Component.Mass"/> <!-- Needed to use components [NodalMassDensity,PrismFEMMass] -->
+        <RequiredPlugin pluginName="Sofa.Component.ODESolver.Backward"/> <!-- Needed to use components [EulerImplicitSolver] -->
+        <RequiredPlugin pluginName="Sofa.Component.SolidMechanics.FEM.Elastic"/> <!-- Needed to use components [PrismCorotationalFEMForceField] -->
         <RequiredPlugin pluginName="Sofa.Component.StateContainer"/> <!-- Needed to use components [MechanicalObject] -->
         <RequiredPlugin pluginName="Sofa.Component.Topology.Container.Constant"/> <!-- Needed to use components [MeshTopology] -->
         <RequiredPlugin pluginName="Sofa.Component.Topology.Container.Grid"/> <!-- Needed to use components [RegularGridTopology] -->
         <RequiredPlugin pluginName="Sofa.Component.Topology.Mapping"/> <!-- Needed to use components [Hexa2PrismTopologicalMapping] -->
         <RequiredPlugin pluginName="Sofa.Component.Visual"/> <!-- Needed to use components [VisualMesh] -->
+        <RequiredPlugin pluginName="Sofa.GL.Component.Rendering3D"/> <!-- Needed to use components [OglSceneFrame] -->
     </Node>
 
     <DefaultAnimationLoop/>
@@ -21,14 +23,12 @@
     <LineAxis size="0.1"/>
     <OglSceneFrame/>
 
-    <EulerImplicitSolver name="backward Euler" rayleighStiffness="0.1" rayleighMass="0.1" />
-    <SparseLDLSolver/>
+    <EulerImplicitSolver name="backward_Euler" rayleighStiffness="0.01" rayleighMass="0.01" />
+    <SparseLDLSolver template="CompressedRowSparseMatrixMat3x3d"/>
 
     <RegularGridTopology name="grid" min="-0.01 -0.01 0" max="0.01 0.01 0.2" n="5 5 30"/>
     <MechanicalObject template="Vec3" name="state" showObject="true"/>
 
-    <MeshMatrixMass massDensity="1100"/>
-
     <Node name="prisms">
         <MeshTopology name="prism_topology"/>
         <Hexa2PrismTopologicalMapping input="@grid" output="@prism_topology" />
@@ -36,6 +36,9 @@
         <PrismCorotationalFEMForceField name="FEM" youngModulus="2e6" poissonRatio="0.45" topology="@prism_topology"
                                         rotationMethod="polar" computeForceStrategy="sequenced" computeForceDerivStrategy="sequenced"/>
 
+        <NodalMassDensity property="1100"/>
+        <PrismFEMMass/>
+
         <VisualMesh position="@../state.position" topology="@prism_topology" enable="true"/>
     </Node>