1. A computer implemented method of 3D modeling, the method comprising: providing in computer memory a finite element model representing a subject structural dynamic system, the finite element model programmed to have mechanical features of the subject 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 the mechanical features of the represented structural dynamic system, forming the improved 3D model of the real world object including modifying one or more properties of the 3D model corresponding to physical properties of the real world object achieving a design goal of the real world object.