I would like represent my object as mass spring mesh to simulate soft body dynamics.

Mass represent vertex while edge represent spring that connect two adjacent vertex.

I

I draw a this simple example to explain my problem.

I have four mass m1,m2,m3,m4 and know the values and their positions.

I know the stiffness coefficient kij and dumping coefficient cij of mesh springs where i and j are the vertex index.

In figure 1 the system is in the rest position.

In figure 2 after apply a force to m4 point the system change configuration,

The user move the m4 point from figure 1 to figure 2 position.

A force applied to m4 move the mass m4.

m1 mass rest in the same position again in figure 2 while mass m2 e m3 have a new position.

I would like calculate the new position of m2 and m3 mass after that user move the m4 mass.

I know the formula about Fi_int the internal force on the vertex i and the damping force Fi_ext on the vertex.

Please help me solve this problem.