1. A method for generating isosurfaces utilizing a digital computer and associated storage means, where (1) a geometric volume, represented by a set of points in three-dimensional space together with connectivity data defining a set of volume elements which subdivide said geometric volume, and (2) a scalar field associated with said set of points, a single scalar value within a range being associated with each point in said set of points, are stored in said storage means, comprising the steps of: (a) subdividing each volume element into a tetraset of linear tetrahedral subelements having triangular faces in such a way that the triangular faces of a given one of the linear tetrahedral subelements that are subdivisions of a face of a first volume element align with the faces of a given one of the tetrahedral subelements of a second volume element sharing the face of the first volume element; (b) subdividing the range of said scalar field into a predefined number of equally spaced value-steps forming a value-step sequence; (c) identifying, for each volume element and for each member of the tetraset associated with a given volume element, which, if any, value-steps are contained within each tetraset member; and (d) generating a set of isofacets for each value-step identified in step (c).