What is the strategy of sub dividing tetrahedron in sofa

[Coco]

Hello everyone，

I want to know the strategy of sub dividing tetrahedron in sofa.But I’m not clear understand the code in the TetrahedronSetTopologyAlgorithems.inl.Can anyone gives me some details?
Best,

Coco

[Hugo]

Hi Coco,

The only implementation described in TetrahedronSetTopologyAlgorithms is a subdivision based on the plane crossing a tetrahedron.
This is pretty limited. You can actually handle your own subdivision of tetrahedron by writing a Component (like TopologicalChangeProcessor) based on the functions available in the TetrahedronSetTopologyModifier.
There you will be able to implement your own subdivision.

Did you already make some progress since December?

Best,

Hugo

[Coco]

Hi Hugo,

I get that the implementation is a subdivision based on the plane crossing a tetrahedron. I just feel confused about the implementation how it constructs subdivided tetrahedrons. Just like here

 //construct subdivided tetrahedrons
        Tetra subTetra[2];
        edgeDirec=this->m_geometryAlgorithms->computeEdgeDirection(intersectedEdgeID[0])*-1;
        Real dot=edgeDirec*planeNormal;

        //inspect the tetrahedron is already subdivided
        if((pointsID[0]>=m_intialNbPoints) && (pointsID[1]>=m_intialNbPoints))
        {
            if((pointsID[0]-m_intialNbPoints)%2==0)
            {
                if(dot>0)
                {
                    subTetra[0][0]=intersectedEdge[0]; subTetra[0][1]=pointsID[0]+1;		subTetra[0][2]=pointsID[1]+1;		subTetra[0][3]=intersectedPointID[0]+1;
                    subTetra[1][0]=intersectedEdge[1]; subTetra[1][1]=pointsID[0];			subTetra[1][2]=pointsID[1];			subTetra[1][3]=intersectedPointID[0];
                }
                else
                {
                    subTetra[0][0]=intersectedEdge[0]; subTetra[0][1]=pointsID[0];			subTetra[0][2]=pointsID[1];			subTetra[0][3]=intersectedPointID[0];
                    subTetra[1][0]=intersectedEdge[1]; subTetra[1][1]=pointsID[0]+1;		subTetra[1][2]=pointsID[1]+1;		subTetra[1][3]=intersectedPointID[0]+1;
                }
            }
            else
            {
                if(dot>0)
                {
                    subTetra[0][0]=intersectedEdge[0]; subTetra[0][1]=pointsID[0];			subTetra[0][2]=pointsID[1];				subTetra[0][3]=intersectedPointID[0]+1;
                    subTetra[1][0]=intersectedEdge[1]; subTetra[1][1]=pointsID[0]-1;		subTetra[1][2]=pointsID[1]-1;			subTetra[1][3]=intersectedPointID[0];
                }
                else
                {
                    subTetra[0][0]=intersectedEdge[0]; subTetra[0][1]=pointsID[0]-1;		subTetra[0][2]=pointsID[1]-1;			subTetra[0][3]=intersectedPointID[0];
                    subTetra[1][0]=intersectedEdge[1]; subTetra[1][1]=pointsID[0];			subTetra[1][2]=pointsID[1];				subTetra[1][3]=intersectedPointID[0]+1;
                }
            }
        }

Why does it need to determine the dot?

In the past two weeks, this problem has been bothering me and I have no progress.

Best,

Coco

[Hugo]

Hi Coco,

Hmm I’m no real expert of these topological changes.
As I understand it, when an intersection between the plane and a tetrahedron is detected, points are added at each intersection between the plane and the edges of the tetrahedron. Then, using these new points, new tetrahedron is created.
I’ll also see if anyone can tell us more about it.

Best,

Hugo

[Coco]

Hi Hugo,

Thank you for always help.It is Lunar New Year now, Wish you all the best and success.

Best,

Coco

[Hugo]

Ahah ! Thank you very much !
Wish you all the best and many SOFA achievements !

Did my reply help ?
Shall we resolve the topic?

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