The constitutive model of a soft body's cells (triangles in 2D, tetrahedra in 3D).
Corotational linear elasticity: a linear material in the cell's rotated frame.
Neo-Hookean hyperelasticity, which resists inversion and large compressions.
Per-cell area/volume preservation constraints (the cell's shape is held by its edges).
The constitutive model of a soft body's cells (triangles in 2D, tetrahedra in 3D).