  This thesis presents a two-layer uniform facet elastic object for real-time
simulation based on physics modeling method. It describes the elastic object
procedural modeling algorithm with particle system from the simplest
one-dimensional object, to more complex two-dimensional and three-dimensional
objects.
  The double-layered elastic object consists of inner and outer elastic mass
spring surfaces and compressible internal pressure. The density of the inner
layer can be set different from the density of the outer layer; the motion of
the inner layer can be opposite to the motion of the outer layer. These special
features, which cannot be achieved by a single layered object, result in
improved imitation of a soft body, such as tissue's liquidity non-uniform
deformation. The construction of the double-layered elastic object is closer to
the real tissue's physical structure.
  The inertial behavior of the elastic object is well illustrated in
environments with gravity and collisions with walls, ceiling, and floor. The
collision detection is defined by elastic collision penalty method and the
motion of the object is guided by the Ordinary Differential Equation
computation.
  Users can interact with the modeled objects, deform them, and observe the
response to their action in real time.
