Dynamic topology change of BarycentricMapping

[drakelzh]

Hello everyone, I am currently using SOFA24.12 version. Using the SOFA tool, I have merged two adjacent spherical obj models into a tetrahedral model in the format of vtu, and assigned two different youngModulus to this tetrahedral model through the local SticknessFactor node of TetrahedronFEMForceField. Through BarycentricMapping, I mapped two spherical models as visual models onto this tetrahedral model. So its mechanical model is a tetrahedral model, while visually it is two models, and I can distinguish between the two regions through MeshROI. This feature has been successfully tested.This feature has been successfully tested, and I left some pictures to illustrate the situation.


Now I have bound a SphereROI at the front end of the instrument to access the merged tetrahedral model, and removed the tetrahedra within the ROI using TetrahedronSetTopologyModifier.

The current problem is that when removing tetrahedra, the two visual models cannot be updated synchronously because they are mapped through BarycentricMapping instead of IdentityMapping. If it is IdentityMapping, then the visual model part will also be updated when removing tetrahedra. But the two visual models cannot be mapped to the tetrahedral model through IdentityMapping, so how can the two visual models of the tetrahedral model be updated synchronously when removing the tetrahedron?
I have tried to reinit the BarycentricMapping corresponding to two visual models, but it is ineffective because the vertices in the visual model does not change during reinit. Removing tetrahedra does not affect the vertices in the visual model mapped by BarycentricMapping. However, the vertices in the tetrahedral model is updated in the handleTopologyChange function in BarycentricMapping. Inl( I think there is a bug with the handleTopologyChange in the BarycentricMapping. inl code updated for this tetrahedron in v24.12, as it did not correctly match the corresponding d_mapper. I have tried other methods to update the vertices of fromModel correctly), so the tetrahedral vertices are updated after removal, but not in the visual model.

I can remove the surface of the visual model using TriangleSetTopologyModifier now, but I haven't figured out how to construct the internal triangular mesh of the visual model yet.
If anyone has good ideas or suggestions, I would greatly appreciate!

[drakelzh]

`

<CollisionPipeline name="pipeline" depth="6" verbose="1"/>
<BruteForceBroadPhase/>
<BVHNarrowPhase/>
<CollisionResponse name="collision response" response="FrictionContactConstraint" />
<LocalMinDistance name="proximity" alarmDistance="0.1" contactDistance="0.05" angleCone="0.01"/>	

<Node name="M1">
	<EulerImplicitSolver rayleighMass="0.01" rayleighStiffness="0.01" />
	<CGLinearSolver iterations="25" tolerance="1e-6" threshold="1e-20"/>
	
	<MeshVTKLoader name="volume" filename="mesh\out.vtu" onlyAttachedPoints="false" translation="0 3 0" scale="0.1" rotation="0 90 0"/>
	<TetrahedronSetTopologyContainer name="TetraContainer" position="@volume.position" tetras="@volume.tetras"/>
	<TetrahedronSetTopologyModifier name="TetraModifier" />
	<TetrahedronSetGeometryAlgorithms template="Vec3d" />	
	
	<MechanicalObject name="mecaObj" template="Vec3d" src="@TetraContainer"/>
	<UniformMass vertexMass="0.1" />
		
	<SphereROI name="detectSphereROI" centers="0 -4 -0.5" radii="1" drawSphere="1" position="@mecaObj.rest_position"
	computeTriangles="1" computeTetrahedra="1" computeEdges="0" />

	<TetrahedronFEMForceField name="FEM" youngModulus="100" poissonRatio="0.4" listening="true" 
       localStiffnessFactor="..........."/> 
	    
	<UncoupledConstraintCorrection name="correction" defaultCompliance="60.0" /> 

	<Node name="CollisionModel">
		<TriangleCollisionModel name="volumeT"/>
		<LineCollisionModel  name="volumeL"/>
		<PointCollisionModel name="volumeP"/>			
	</Node>
		
	<PlaneForceField normal="0 1 0" d="-20.2" stiffness="1000"  showPlane="1" showPlaneSize="100" />

	<SphereROI centers="0 -1 -0.5" name="FixedROI" radii="3" drawSphere="0"  />
	<FixedProjectiveConstraint name="FixedConstraint1" indices="@FixedROI.indices" />
</Node>

<Node name="MeshROI1"  >
    <MeshOBJLoader name="ROIloader" filename="mesh/sphere_0_0_skin.obj" scale="0.1" translation="0 3 0" rotation="0 90 0"/>
	
	<TriangleSetTopologyContainer name="VisualContainer" src="@ROIloader"/>		
	<TriangleSetTopologyModifier name="VisualModifier"/>
	<TriangleSetGeometryAlgorithms name="GeomAlgo" template="Vec3d" drawEdges="0" drawTriangles="0" showIndicesScale="0.01" showTriangleIndices="0" showPointIndices="0"/>
	
	<MechanicalObject name="dofsA" src="@VisualContainer" />
	<OglModel name="Visual"  color="red"/>
	<BarycentricMapping name="BM1" template="Vec3d,Vec3d" input="@../M1/mecaObj" output="@Visual" printLog="1"/>
	
</Node>

<Node name="MeshROI2"  >
    <MeshOBJLoader name="ROIloader" filename="mesh/sphere_10_0_bone.obj" scale="0.1" translation="0 3 0" rotation="0 90 0"/>
	
	<TriangleSetTopologyContainer name="VisualContainer" src="@ROIloader"/>		
	<TriangleSetTopologyModifier name="VisualModifier"/>
	<TriangleSetGeometryAlgorithms name="GeomAlgo" template="Vec3d" drawEdges="0" drawTriangles="0" showIndicesScale="0.01" showTriangleIndices="0" showPointIndices="0"/>
	
	<MechanicalObject name="dofsB" src="@VisualContainer" />
    <OglModel name="Visual" color="green"/>
	<BarycentricMapping name="BM2" template="Vec3d,Vec3d" input="@../M1/mecaObj" output="@Visual" printLog="1" />
	
</Node>

<MeshROI name="ROIm" drawBox="1" drawEdges="0" drawTriangles="1" drawTetrahedra="0" drawOut="1" computeMeshROI="1"  doUpdate="1"
 position="@M1/mecaObj.position" tetrahedra="@M1/volume.tetrahedra" ROIposition="@MeshROI2/ROIloader.position" ROItriangles="@MeshROI2/ROIloader.triangles" 
/>

`

[hugtalbot]

Hi @drakelzh and happy new year 2️⃣ 0️⃣ 2️⃣ 6️⃣
✨ ✨ ✨ ✨ ✨ ✨

I have a few questions, I am sorry:

• why using two visual models for the surface of the object?
• have you given a try to the SofaCarving plugin ?

Do not need to have a specific texture inside the object?
Sorry not to solve straightaway your topic.

[drakelzh]

Thank you for your reply. The reason I used this method is to achieve mutual influence among multiple organizations. However, I have now fulfilled my requirements based on the spring approach, so I will close this topic.
Happy New Year!