  We propose a new approach allowing visio-haptic interaction with a FE model
of a human liver having both non-linear geometric and material properties. The
material properties used in the model are extracted from the experimental data
of pig liver to make the simulations more realistic. Our computational approach
consists of two main steps: a pre-computation of the configuration space of all
possible deformation states of the model, followed by the interpolation of the
precomputed data for the calculation of the reaction forces displayed to the
user through a haptic device during the real-time interactions. No a priori
assumptions or modeling simplifications about the mathematical complexity of
the underlying soft tissue model, size and irregularity of the FE mesh are
necessary. We show that deformation and force response of the liver in
simulations are heavily influenced by the material model, boundary conditions,
path of the loading and the type of function used for the interpolation of the
pre-computed data.
