the simulation of the large deformation of 3-D objects subject
to dynamic and static loads. For static analysis, their model
achieved model reduction primarily with the use of a graded
mesh consisting of small elements at the exterior and large
element in the interior. De and co-workers [23] proposed to
use finite spheres method as a meshless scheme for real-time
medical simulation. The governing equations of elasticity were
numerically solved by the method of collocation at the nodal
points, which were placed near the surgical tool tip [24].