Hi Steve,
it depends. If you use TetrahedronFEMForceField, you can give a vector of real for the young modulus. Each value is associated to an element. So it means the vector must be the size of the number of element (and probably in the same order). If the values are stored in the cell data of a vtk file, you can refer to them with youngModulus=”@vtkLoader.cellData” or something similar (sorry I couldn’t test).
However, I just noticed that HexahedronFEMForceField requires only one scalar value, which means the material must be homogeneous.
Hope this helps,
Alex