1. A method of converting an unstructured finite element grid to a grid of voxel data, said grid of voxel data to be displayed on a display device, said method comprising the steps of: inputting data representing said unstructured finite element grid, wherein said unstructured finite element grid represents a three-dimensional object; performing a plurality of slicing operations upon said unstructured finite element grid in a viewing direction; generating, during each slicing operation, intersection polygons with scalar data at polygon vertices; mapping, during each slicing operation, each of said scalar data to shades of a color; generating, during each slicing operation, a two-dimensional array of pixel colors from said shades of a color; and reading back said two-dimensional array of pixel colors from a frame buffer such that each pixel represents a three dimensional point voxel corner.