1. A computer implemented method of modeling mechanical features of a structural dynamic system, the method comprising: providing in computer memory a finite element model representing a structural dynamic system; in a processor coupled to the computer memory, solving a system of equations with a first term representing a linear combination of a mass, a stiffness, and a damping of the finite element model and a second term representing modal damping, the system of equations solved using a Sherman-Morrison-Woodbury formula or a preconditioned iterative method; and forming an improved 3D model of a real world object based on the finite element model by utilizing results of the solved system of equations with the finite element model and modal damping to model mechanical features of the represented structural dynamic system.