Pressure Model of Soft Body Simulation
  Motivated by existing models used for soft body simulation which are rather complex to implement, we present a novel technique which is based on simple laws of physics and gives high quality results in real-time. We base the implementation on simple thermodynamics laws and use the Clausius-Clapeyron state equation for pressure calculation. In addition, this provides us with a pressure force that is accumulated into a force accumulator of a 3D mesh object by using an existing spring-mass engine. Finally after integration of Newtons second law we obtain the behavior of a soft body with fixed or non-fixed air pressure inside of it. 
Matyka Maciej, Ollila Mark