1. A computer-implemented method for use in designing an arbitrarily shaped physical object using a computer-assisted design (CAD) system, the arbitrarily shaped physical object having a volume, the CAD system having a keyboard, screen display, pointing device, processor, and memory, the method comprising the steps of: (a) using the CAD system, designing a surface definition of the object, the surface definition having an electronic form that can be electronically manipulated in the memory and from which the CAD system can create and display a visual representation of the object; (b) storing the surface definition in an electronic form in a digital storage medium; and (c) using a computer, obtaining the electronic form of the surface definition from the digital storage medium and automatically producing an electronic form of a boundary fitted hexahedral grid for filling the volume of the object with a plurality of hexahedral grid elements, the boundary fitted hexahedral grid conformal to the surface definition.