In this report, we describe models and algorithms designed to produce efficient and physically consistent dynamic simulations. These models and algorithms have been implemented in a unique framework, modeling both deformations and contacts through visco-elastic relations. Since this model of interaction (known as «penalty based») is much debated, we present a compared study of two contact models; «penalty» and «impulse». Indeed, the «penalty» based model is supposed to have two major drawbacks : - determin- ing the visco-elastic parameters and - choosing the computation time step. We present a solution for both problems based on physical concepts. Finally, we will present results comparing real data, «impulse» based simulation and «penalty» based simulation.