Techniques for displaying 3D isovalues of scalar fields such as stress within a solid finite-element model generally involve examining each element for values of interest. An inexpensive, straightforward method is discussed for reducing the number of elements searched for such isovalues. It takes advantage of one traversal of the element data to yield a compact classification of the model by result values and ranges, with no sorting required. This data structure can then relate any scalar isovalue to a set of element groups which are closely inclusive of the isovalue. This method is intended for applications requiring repeated access to the analysis data, such as animation and interactive rendering of isosurfaces and scalar fields. While applicable to general volume visualization problems, it is particularly well suited to optimizing real-valued continuum field results such as those found in finite-element data.>

We have developed a technique that extends existing 3-D result visualization methods for use with discretized volumes such as finite element models, where result values are only available at coarsely spaced points throughout the volume. It represents results as smooth isosurfaces within the volume for one or more result values, using visually continuous, bi-cubic polynomials.At each of the points where results are available, result gradients are calculated by a finite difference procedure. The result values and result gradients are used to obtain the location of and the tangents to the isosurfaces on lines connecting the result points. Continuous doubly curved surfaces and surface normals are constructed separately between these discrete isosurface points using bi-cubic polynomials. The isosurfaces are rendered with standard light-source shading and optional levels of translucency, surrounded by translucent free faces of the structure.The method generates isosurfaces on an element-by-element basis, without reference at display time to the behavior of neighboring elements. It is intended for high speed display-time processing of either static or varying isosurface values.